HK1250709B - Novel oxathiolane carboxylic acids and derivatives for the treatment and prophylaxis of virus infection - Google Patents

Description

New oxathiolane carboxylic acids and their derivatives for treating and preventing viral infections

The present invention relates to novel oxathiolane carboxylic acid compounds and their corresponding derivatives and prodrugs having Toll-like receptor agonist activity, their preparation methods, pharmaceutical compositions containing them and their potential use as drugs.

Field of the Invention

The present invention relates to compounds of formula (I) and (Ia),

and their prodrugs, compounds of formula (II) and (IIa),

wherein R ¹ to R ⁵ , W and A are as described below, or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof.

Toll-like receptors (TLRs) recognize a wide range of conserved pathogen-associated molecular patterns (PAMPs). They play a crucial role in detecting invading pathogens and subsequently initiating innate immune responses. There are 10 known members of the TLR family in humans. These are type I transmembrane proteins characterized by a leucine-rich extracellular domain and a cytoplasmic tail containing the conserved Toll/interleukin (IL)-1 receptor (TIR) domain. Within this family, TLR3, TLR7, TLR8, and TLR9 are located within endosomes. TLR7 can be activated by binding to specific small molecule ligands (i.e., TLR7 agonists) or its natural ligand (i.e., single-stranded RNA, ssRNA). Upon ssRNA binding to TLR7, the dimerized form of the receptor is thought to undergo structural changes, leading to the subsequent recruitment of adaptor proteins to its cytoplasmic domain, including myeloid differentiation primary response gene 88 (MyD88). After the receptor signaling cascade is initiated through the MyD88 pathway, cytoplasmic transcription factors such as interferon regulatory factor 7 (IRF-7) and nuclear factor kappa B (NF-κB) are activated. These transcription factors then translocate to the nucleus and initiate the transcription of various genes, such as IFN-α and other antiviral cytokine genes. TLR7 is mainly expressed on plasmacytoid cells and is also expressed on B-cells. Altered immune cell responsiveness may be associated with the decline in innate immune responses during chronic viral infection. Agonist-induced TLR7 activation may thus represent a new approach for treating chronic viral infections (D.J Connolly and L.AJ O'Neill, Current Opinion in Pharmacology 2012, 12: 510-518, P.A. Roethle et al., J. Med. Chem. 2013, 56, 7324-7333).

Current therapies for chronic HBV infection are based on two distinct classes of drugs: traditional antiviral nucleoside (nucleotide) analogs and the more recent pegylated interferon α (PEG-IFN-α). Oral nucleoside (nucleotide) analogs work by inhibiting HBV replication. This is a lifelong treatment course, during which drug resistance often develops. As an alternative, pegylated interferon α (PEG-IFN-α) has been used to treat some chronically infected HBV patients for a limited duration of treatment. Although HBeAg seroconversion has been achieved in at least a small proportion of HBV patients, adverse reactions make it difficult to tolerate. Notably, functional cure, defined as HBsAg seroconversion, is extremely rare with both current therapies. Therefore, there is an urgent need for a new generation of therapeutic options to achieve functional cure in HBV patients. Treatment with oral TLR7 agonists represents a promising solution, offering higher efficacy and better tolerability. Pegylated IFN-α (PEG-IFN-α) is currently used to treat chronic HBV and is an alternative to the potential need for lifelong use of antiviral nucleoside (acid) analogs. In a small group of chronic HBV patients, PEG-IFN-α therapy can induce persistent immune control of the virus after a limited course of treatment. However, the percentage of HBV patients who achieve seroconversion using interferon therapy is low (up to 27% for HBeAg-positive patients), and the treatment is generally poorly tolerated. In addition, functional cure (defined as HBsAg disappearance and seroconversion) is also extremely uncommon when treated with PEG-IFN-α and nucleoside (acid). Due to these limitations, there is an urgent need for improved treatment options for treating and inducing functional cure of chronic HBV. Treatment with oral small molecule TLR7 agonists is a promising approach with the potential to provide higher efficacy and tolerance (T.Asselah et al., Clin Liver Dis 2007, 11, 839-849).

Indeed, several identified TLR7 agonists have been considered for therapeutic purposes. To date, imiquimod (ALDARA ^™ ) is a TLR7 agonist approved by the US FDA for the treatment of human papillomavirus-induced skin lesions. The TLR7/8 dual agonist resiquimod (R-848) and the TLR7 agonist 852A have been evaluated for the treatment of human genital herpes and chemotherapy-refractory metastatic melanoma, respectively. ANA773 is an oral prodrug TLR7 agonist being developed to treat patients with chronic hepatitis C virus (HCV) infection and chronic hepatitis B infection. GS-9620 is an orally active TLR7 agonist. A Phase Ib study demonstrated that treatment with GS-9620 was safe, well-tolerated, and resulted in dose-dependent induction of ISG15 mRNA in patients with chronic hepatitis B (EJ Gane et al., Annu Meet AmAssoc Study Liver Dis (November 1-5, Washington, DC) 2013, Abstract 946). Therefore, there is an urgent clinical need to develop effective and safe TLR7 agonists as new HBV treatments to provide more treatment options or replace existing partially effective treatments.

SUMMARY OF THE INVENTION

The present invention provides a series of novel 3-substituted 5-amino-6H-thiazolo[4,5-d]pyrimidine-2,7-dione compounds and their prodrugs having Toll-like receptor agonist activity. The present invention also provides the biological activity of these compounds in inducing increased SEAP levels by activating Toll-like receptors, such as the TLR7 receptor, and the metabolic conversion of the prodrugs to the parent compounds in the presence of human hepatocytes. Furthermore, the present invention provides the therapeutic or prophylactic use of these compounds and pharmaceutical compositions containing these compounds and their prodrugs in the treatment or prevention of infectious diseases, such as HBV or HCV. The present invention also provides compounds with superior activity.

The present invention relates to novel compounds of formula (I) and (Ia) or pharmaceutically acceptable salts, enantiomers or diastereomers thereof,

in

^R1 is OH;

^R2 is H;

R ³ is H, C _1-6 alkyl, C _2-6 alkenyl or C _3-7 cycloalkyl;

W is -CH ₂ - or -C(C _1-6 alkyl) ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or heterocyclic amino.

The present invention also relates to prodrugs of formula (II) and (IIa) or pharmaceutically acceptable salts, enantiomers or diastereomers thereof,

in

R ⁴ is H, C _1-6 alkylcarbonyl, phenylcarbonyl or C _1-6 alkylphenylcarbonyl;

^R5 is H, _C1-6 alkyl, _C2-6 alkenyl or _C3-7 cycloalkyl;

W is -CH ₂ - or -C(C _1-6 alkyl) ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or heterocyclic amino.

The present invention also relates to methods for preparing the compounds, medicaments based on the compounds of the present invention and methods for producing the same, and the use of compounds of formula (I) or (Ia) or prodrugs thereof of formula (II) or (IIa) as TLR7 agonists. Therefore, compounds of formula (I) and (Ia) or prodrugs thereof of formula (II) and (IIa) can be used to treat or prevent HBV and/or HCV infection by utilizing Toll-like receptor agonism.

Detailed Description of the Invention

Unless otherwise defined, all technical and scientific terms used herein have the meaning commonly understood by those skilled in the art to which the invention belongs. In addition, the following definitions are listed to illustrate and define the meaning and scope of the various terms used to describe the present invention.

definition

The term "C _1-6 alkyl" as used herein refers to a saturated straight-chain or branched alkyl group containing 1 to 6, particularly 1 to 4, carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc. Specific "C _1-6 alkyl" groups are methyl, ethyl and n-propyl.

The term "heterocyclyl" refers to a monovalent saturated or partially unsaturated monocyclic or bicyclic ring system of 3-10 ring atoms, comprising 1-5 ring heteroatoms selected from N, O and S, the remaining ring atoms being carbon. In a specific embodiment, the heterocyclyl is a monovalent saturated monocyclic ring system of 4-7 ring atoms, comprising 1, 2 or 3 ring heteroatoms selected from N, O and S, the remaining ring atoms being carbon. Examples of monocyclic saturated heterocyclyls are aziridine, oxirane, azetidinyl, oxetanyl, pyrrolidinyl, tetrahydrofuranyl, tetrahydrothiophenyl, pyrazolidinyl, imidazolidinyl, oxazolidinyl, isoxazolidinyl, thiazolidinyl, piperidinyl, tetrahydropyranyl, tetrahydrothiopyranyl, piperazinyl, morpholinyl, thiomorpholinyl, dioxothiomorpholinyl, azepanyl, diazepanyl, homopiperazinyl or oxazepanyl. Examples of bicyclic saturated heterocycles are azabicyclo[3.2.1]octyl, quinuclidinyl, oxazabicyclo[3.2.1]octyl, azabicyclo[3.3.1]nonyl, oxazabicyclo[3.3.1]nonyl or thiazabicyclo[3.3.1]nonyl. Examples of partially unsaturated heterocycles are dihydrofuranyl, imidazolinyl, dihydrooxazolyl, tetrahydropyridinyl or dihydropyranyl.

The term "heterocyclic amino" denotes an amino group having a nitrogen atom in a heterocyclic ring. Examples of heterocyclic amino groups are pyrrolidinyl, piperidinyl or morpholinyl.

The term " _C2-6 alkenyl" means an unsaturated straight or branched alkenyl group containing 2 to 6, especially 2 to 4 carbon atoms, such as vinyl, propenyl, allyl, butenyl, etc. Specific " _C2-6 alkenyl" groups are allyl and vinyl.

The term "C _3-7 cycloalkyl", alone or in combination, denotes a saturated carbocyclic ring containing 3 to 7 carbon atoms, in particular 3 to 6 carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, etc. A specific "C _3-7 cycloalkyl" group is cyclopropyl.

The term "C _1-6 alkoxy" refers to the group C _1-6 alkyl-O-, wherein "C _1-6 alkyl" is as defined above. Particular "C _1-6 alkoxy" groups are methoxy or ethoxy.

The term "carbonyl" alone or in combination signifies the group -C(O)-.

The term "C _1-6 alkylcarbonyl" refers to the group C _1-6 alkyl-C(O)-, wherein "C _1-6 alkyl" is as defined above. A specific "C _1-6 alkylcarbonyl" group is acetyl.

The term "enantiomers" refers to two stereoisomers of a compound that are non-superimposable mirror images of one another.

The term "diastereomer" refers to stereoisomers that have two or more chiral centers and whose molecules are not mirror images of one another. Diastereomers have different physical properties, such as melting points, boiling points, spectral characteristics, and reactivities.

The term "pharmaceutically acceptable salts" refers to salts that are not biologically or otherwise undesirable. Pharmaceutically acceptable salts include acid and base addition salts.

The term "pharmaceutically acceptable acid addition salts" denotes those pharmaceutically acceptable salts formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, carbonic acid, phosphoric acid and organic acids selected from aliphatic, alicyclic, aromatic, araliphatic, heterocyclic, carboxylic and organic sulfonic acids such as formic acid, acetic acid, propionic acid, glycolic acid, gluconic acid, lactic acid, pyruvic acid, oxalic acid, malic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, aspartic acid, ascorbic acid, glutamic acid, anthranilic acid, benzoic acid, cinnamic acid, mandelic acid, pamoic acid, phenylacetic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid and salicylic acid.

The term "pharmaceutically acceptable base addition salt" refers to those pharmaceutically acceptable salts formed with organic or inorganic bases. Examples of acceptable inorganic bases include sodium, potassium, ammonium, calcium, magnesium, iron, zinc, copper, manganese and aluminum salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary and tertiary amines; substituted amines, including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, 2-diethylaminoethanol, trimethylamine (trimethamine), dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine (hydrabamine), choline, betaine, ethylenediamine, glucosamine, methylglucamine, theobromine, purines, piperazine, piperidine, N-ethylpiperidine and polyamine resins.

Compounds of formula (I) or (Ia) and their prodrugs containing one or more chiral centers may exist as racemates, diastereomeric mixtures or optically active single isomers. Racemates can be separated into enantiomers according to known methods. In particular, diastereomeric salts that can be separated by crystallization are formed from the racemic mixture by reaction with an optically active acid such as D- or L-tartaric acid, mandelic acid, malic acid, lactic acid or camphorsulfonic acid.

The compounds of the present invention may exhibit tautomerism. Although the structural formulas do not explicitly depict all possible tautomeric forms, it should be understood that they are intended to represent any tautomeric form of the depicted compound, and are not limited to the specific compound depicted by the structural formula. For example, with respect to Formula (III), it should be understood that regardless of whether its substituents are shown in their enol or keto form, they represent the same compound (as shown in the examples below).

_Rx refers to any possible substituent.

Certain compounds of the present invention may exist as single stereoisomers (i.e., substantially free of other stereoisomers), racemates, and/or mixtures of enantiomers and/or diastereomers. All such single stereoisomers, racemates, and mixtures thereof are within the scope of the present invention. Preferably, the optically active compounds of the present invention are used in optically pure form. As generally understood by those skilled in the art, an optically pure compound having one chiral center (i.e., one asymmetric carbon atom) is a compound consisting essentially of one of the two possible enantiomers (i.e., enantiomerically pure), and an optically pure compound having more than one chiral center is a compound that is both diastereomerically pure and enantiomerically pure. Preferably, the compounds of the present invention are used in a form that is at least 90% optically pure, i.e., a form containing at least 90% of a single isomer (80% enantiomeric excess ("e.e.") or diastereomeric excess ("d.e.")), more preferably at least 95% (90% e.e. or d.e.), even more preferably at least 97.5% (95% e.e. or d.e.), and most preferably at least 99% (98% e.e. or d.e.). In addition, the compounds of Formula (I) and (Ia), and their prodrugs Formula (II) and (IIa), as well as other compounds of the present invention, are intended to encompass solvated and unsolvated forms of the defined structures. For example, Formula (I) or (Ia) includes compounds of the shown structures in both hydrated and unhydrated forms. Other examples of solvates include structures in combination with isopropanol, ethanol, methanol, DMSO, ethyl acetate, acetic acid, or ethanolamine.

The term "prodrug" refers to a form or derivative of a compound that is metabolized in vivo, for example, by a subject's biological fluids or enzymes, to produce a pharmacologically active form of the compound after administration to produce the desired pharmacological effect. Prodrugs are described, for example, in "The Organic Chemistry of Drug Design and Drug Action", Richard B. Silverman, Academic Press, San Diego, 2004, Chapter 8: Prodrugs and Drug Delivery Systems, pp. 497-558.

"Pharmacologically active metabolites" refer to pharmacologically active products produced by the metabolism of a specific compound or salt thereof in the body. Once in the body, most drugs serve as substrates for chemical reactions that alter their physical properties and biological effects. These metabolic transformations often affect the polarity of the compounds of the invention, altering how the drug is distributed and excreted from the body. However, in some cases, drug metabolism is necessary for its therapeutic effect.

The term "therapeutically effective amount" means an amount of a compound or molecule of the invention which, when administered to a subject, produces the following effects: (i) treatment or prevention of a specific disease, condition, or disorder; (ii) alleviation, amelioration, or elimination of one or more symptoms of a specific disease, condition, or disorder; or (iii) prevention or delay of the onset of one or more symptoms of a specific disease, condition, or disorder as described herein. The therapeutically effective amount will vary depending on the compound, the disease state being treated, the severity of the disease being treated, the age and relative health of the subject, the route and form of administration, the judgment of the attending physician or veterinary practitioner, and other factors.

The term "pharmaceutical composition" refers to a mixture or solution comprising a therapeutically effective amount of an active pharmaceutical ingredient and a pharmaceutically acceptable excipient, ready for administration to a mammal, such as a human, in need thereof.

TLR7 agonists and prodrugs

The present invention relates to compounds of formula (I) or pharmaceutically acceptable salts, enantiomers or diastereomers thereof,

in

^R1 is OH;

^R2 is H;

^R3 is H, _C1-6 alkyl, _C2-6 alkenyl or _C3-7 cycloalkyl;

W is -CH ₂ - or -C(C _1-6 alkyl) ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or heterocyclic amino.

Another embodiment of the present invention is (ii) a compound of formula (I) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

^R1 is OH;

^R2 is H;

^R3 is H, methyl, ethyl, butyl, allyl or cyclopropyl;

W is -CH ₂ - or -C(CH ₃ ) ₂ -;

A is OH, methoxy, CH ₃ NH—, (CH ₃ ) ₂ N—, or morpholinyl.

Another embodiment of the present invention is (iii) a compound of formula (Ia) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof,

in

^R1 is OH;

^R2 is H;

R ³ is H, C _1-6 alkyl, C _2-6 alkenyl or C _3-7 cycloalkyl;

W is -CH ₂ - or -C(C _1-6 alkyl) ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or heterocyclic amino.

Another embodiment of the present invention is (iv) a compound of formula (Ia) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

^R1 is OH;

^R2 is H;

^R3 is H, methyl, ethyl, butyl, allyl or cyclopropyl;

W is -CH ₂ - or -C(CH ₃ ) ₂ -;

A is OH, methoxy, CH ₃ NH—, (CH ₃ ) ₂ N—, or morpholinyl.

Another embodiment of the present invention is (v) a compound of formula (I) or (Ia), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein R ³ is C _1-6 alkyl, C _2-6 alkenyl or C _3-7 cycloalkyl.

Another embodiment of the present invention is (vi) a compound of formula (I) or (Ia), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein R ³ is methyl, ethyl, cyclopropyl or allyl.

Another embodiment of the present invention is (vii) a compound of formula (I) or (Ia), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein W is _-CH2- .

Another embodiment of the present invention is (viii) a compound of formula (I) or (Ia) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

^R1 is OH;

^R2 is H;

R ³ is C _1-6 alkyl or C _3-7 cycloalkyl;

W is -CH ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or morpholinyl.

Another embodiment of the present invention is (ix) a compound of formula (I) or (Ia) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

^R1 is OH;

^R2 is H;

^R3 is methyl, ethyl or cyclopropyl;

W is -CH ₂ -;

A is OH, methoxy, CH ₃ NH—, (CH ₃ ) ₂ N—, or morpholinyl.

Another embodiment of the present invention is (x), wherein the specific compound of formula (I) or (Ia) is the following compound or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof:

Methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetate;

Methyl 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-hydroxymethyl)-1,3-oxathiolan-4-yl]acetate;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid;

2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide;

2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-N,N-dimethylacetamide; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate, methyl ester;

methyl 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate;

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide;

2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide;

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide;

2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide;

5-amino-3-[(4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione;

5-amino-3-[(2S,4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione;

Methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetate;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypentyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxybut-3-enyl]-1,3-oxathiolan-4-yl]acetic acid;

methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetate;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[5-(5-Amino-7-hydroxy-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-2-methyl-propionic acid.

Another embodiment of the present invention is (xi), wherein the more specific compound of formula (I) or (Ia) is the following compound or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof:

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid;

2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid;

methyl 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate;

methyl 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate;

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide;

2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide;

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide;

2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide;

5-amino-3-[(4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione;

5-amino-3-[(2S,4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetic acid;

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetic acid.

Another embodiment of the present invention is (xii) a compound of formula (II) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof,

in

R ⁴ is H, C _1-6 alkylcarbonyl, phenylcarbonyl or C _1-6 alkylphenylcarbonyl;

^R5 is H, _C1-6 alkyl, _C2-6 alkenyl or _C3-7 cycloalkyl;

W is -CH ₂ - or -C(C _1-6 alkyl) ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or heterocyclic amino.

Another embodiment of the present invention is (xiii) a compound of formula (II) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

^R4 is H, acetyl, phenylcarbonyl or methylphenylcarbonyl;

^R5 is H, methyl, ethyl, butyl, allyl or cyclopropyl;

W is -CH ₂ - or -C(CH ₃ ) ₂ -;

A is OH, methoxy, CH ₃ NH—, (CH ₃ ) ₂ N—, or morpholinyl.

Another embodiment of the present invention is (xiv) a compound of formula (IIa) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof,

in

R ⁴ is H, C _1-6 alkylcarbonyl, phenylcarbonyl or C _1-6 alkylphenylcarbonyl;

^R5 is H, _C1-6 alkyl, _C2-6 alkenyl or _C3-7 cycloalkyl;

W is -CH ₂ - or -C(C _1-6 alkyl) ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or heterocyclic amino.

Another embodiment of the present invention is (xv) a compound of formula (IIa) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

^R4 is H, acetyl, phenylcarbonyl or methylphenylcarbonyl;

^R5 is H, methyl, ethyl, butyl, allyl or cyclopropyl;

W is -CH ₂ - or -C(CH ₃ ) ₂ -;

A is OH, methoxy, CH ₃ NH—, (CH ₃ ) ₂ N—, or morpholinyl.

Another embodiment of the present invention is (xvi) a compound of formula (II) or (IIa), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein R ⁴ is phenylcarbonyl.

Another embodiment of the present invention is (xvii) a compound of formula (II) or (IIa), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein R ⁵ is C _1-6 alkyl, C _2-6 alkenyl or C _3-7 cycloalkyl.

Another embodiment of the present invention is (xviii) a compound of formula (II) or (IIa), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein R ⁵ is methyl, ethyl, cyclopropyl or allyl.

Another embodiment of the present invention is (xix) a compound of formula (II) or (IIa), or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein W is _-CH2- .

Another embodiment of the present invention is (xx) a compound of formula (II) or (IIa) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

R ⁴ is phenylcarbonyl;

^R5 is _C1-6 alkyl or _C3-7 cycloalkyl;

W is -CH ₂ -;

A is OH, C _1-6 alkoxy, C _1-6 alkylNH-, (C _1-6 alkyl) ₂ N-, or morpholinyl.

Another embodiment of the present invention is (xxi) a compound of formula (II) or (IIa) or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof, wherein

R ⁴ is phenylcarbonyl;

^R5 is methyl, ethyl or cyclopropyl;

W is -CH ₂ -;

A is OH, methoxy, CH ₃ NH—, (CH ₃ ) ₂ N—, or morpholinyl.

Another embodiment of the present invention is (xxii), wherein the specific compound of formula (II) or (IIa) is [(1S)-1-[(2S,4S,5R)-5-(5-amino-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl] benzoate; or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof.

synthesis

The compounds of the present invention can be prepared by any conventional means. Suitable methods for synthesizing these compounds and their starting materials are provided in the following schemes and examples. Unless otherwise indicated, all substituents, particularly R ¹ to R ⁵ , are as defined above. In addition, unless otherwise explicitly stated, all reactions, reaction conditions, abbreviations and symbols have the meanings familiar to those of ordinary skill in the art of organic chemistry.

Process 1:

^Ra is H or ^R1 ; ^R6 and ^R7 are independently selected from H and _C1-6 alkyl, or together with the nitrogen to which they are attached form a heterocyclic amino group.

As shown in Scheme 1, the synthesis of the present invention begins with benzoyloxyacetaldehyde IV and mercaptosuccinic acid V, which are refluxed with a catalytic amount of an acid such as p-TsOH in an organic solvent such as toluene to produce carboxylic acid VI. Esterification of carboxylic acid VI is carried out in the presence of a coupling agent such as CDI or with _TMSCHN to produce ester VII. Ester VII is further _reduced with a reducing agent such as LiAlH(Ot-Bu) to produce hemiacetal VIII. Hemiacetal VIII is acylated with an anhydride such as acetic anhydride to produce compound IX. Compound IX is coupled with compound X in the presence of a suitable silyl etherifying agent such as N,O-bis(trimethylsilyl)acetamide (BSA) and a Lewis acid such as TMSI to produce compound XI. Compound XI is deprotected under alkaline conditions (e.g., _KCO in _MeOH ) to produce compound XII, which is further separated by preparative HPLC to produce compounds P1 and P2. Compound XII is hydrolyzed under alkaline conditions (e.g., aqueous LiOH solution) to produce carboxylic acid XIII, which is further separated by preparative HPLC to give compounds P3 and P4. Carboxylic acid XIII is coupled with ^R6R7NH in the presence of a coupling agent such as HATU ^to give amide compound XIV, which is further separated by preparative HPLC to give compounds P5 and P6.

Process 2:

^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 .

As shown in Scheme 2, the synthesis can also begin with aldehyde XV (synthesis see: J. Am. Chem. Soc. 2009, 131, 3450-3451) and mercaptosuccinic acid V, which are then refluxed with a catalytic amount of an acid such as p-TsOH in an organic solvent such as toluene to produce compound XVI. Esterification of the carboxylic acid of compound XVI is carried out in the presence of _a coupling agent such as CDI or with TMSCHN to produce ester XVII. Ester XVII is further reduced with _a reducing agent such as LiAlH(Ot-Bu) to produce hemiacetal XVIII. The hemiacetal is acylated with an anhydride such as acetic anhydride to produce compound XIX. Compound XIX is coupled with compound X in the presence of a suitable silyl etherifying agent such as N,O-bis(trimethylsilyl)acetamide (BSA) and a Lewis acid such as TMSI to produce compound XX. Compound XX is deprotected under alkaline conditions (e.g., _KCO in _MeOH ) to produce compound P7. Compound P7 is hydrolyzed under basic conditions (eg, aqueous LiOH) to produce carboxylic acid P8.

Process 3

^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ; ^R6 and ^R7 are independently selected from H and _C1-6 alkyl, or together with the nitrogen to which they are attached form a heterocyclic amino group.

As shown in Scheme 3, the synthesis can also start from aldehyde XV (synthesis see: J. Am. Chem. Soc. 2009, 131, 3450-3451) and (S)-2-mercaptosuccinic acid XXI, which are refluxed with a catalytic amount of an acid such as p-TsOH in an organic solvent such as toluene to produce compound XXII. Carboxylic acid XXII is esterified in the presence of a coupling agent such as CDI or with _TMSCHN to produce ester XXIII. Ester XXIII is further reduced with a reducing agent such as LiAlH(Ot-Bu) to produce hemiacetal XXIV. _Hemiacetal XXIV is acylated with an anhydride such as acetic anhydride to produce compound XXV. Compound XXV is coupled with compound X in the presence of a suitable silyl etherifying agent such as N,O-bis(trimethylsilyl)acetamide (BSA) and a Lewis acid such as TMSI to produce compound XXVI. Compound XXVI was deprotected under basic conditions (e.g., _K₂CO₃ in _MeOH ) to afford compound XXVII, which was further separated by preparative HPLC to afford compounds P9 and P10. Compound XXVII was hydrolyzed under basic conditions (e.g., aqueous LiOH) to afford carboxylic acid XXVIII, which was further separated by preparative HPLC ^to afford compounds P11 and P12. Carboxylic acid XXVIII was coupled with ^R₆R₇NH in the presence of a coupling agent such as HATU to afford amide compound XXIX, which was further separated by preparative HPLC to afford compounds P13 and P14.

The present invention also relates to a method for preparing a compound of formula (I), (Ia), (II) or (IIa), comprising the following reaction:

(a) reacting a compound of formula (XI) with a base,

wherein ^Ra is H or ^R1 ;

(b) reacting a compound of formula (XII) with a base,

wherein ^Ra is H or ^R1 ;

(c) reacting the compound of formula (XIII) with R ⁶ R ⁷ NH in the presence of a coupling agent,

wherein ^Ra is H or ^R1 ;

(d) reacting a compound of formula (P7) with a base,

wherein ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ;

(e) reacting a compound of formula (XXVI) with a base,

wherein ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ;

(f) reacting a compound of formula (XXVII) with a base,

wherein ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ;

(g) reacting a compound of formula (XXVIII) with R ⁶ R ⁷ NH in the presence of a coupling agent,

wherein ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ;

(h) reacting a compound of formula (XXV) with compound X in the presence of a silyl etherifying agent and a Lewis acid,

wherein R ^b is R ³ or R ⁵ ;

or wherein Ra, ^Rb , ^{R1 , R2} , ^R3 , ^R5 , ^R6 and ^R7 are as defined above.

In steps (a) and (e), the base may be, for example, K ₂ CO ₃ .

In steps (b), (d) and (f), the base may be, for example, LiOH.

In steps (c) and (g), the coupling agent may be, for example, HATU.

In step (h), the silyl etherification agent may be, for example, BSA, and the Lewis acid may be, for example, TMSI.

The compounds of formula (I), (Ia), (II) and (IIa) prepared according to the above-mentioned process are also an object of the present invention.

Pharmaceutical compositions and administration

Another embodiment provides a pharmaceutical composition or medicine containing a compound of the present invention and a therapeutically inert carrier, diluent or excipient, and methods for preparing these compositions and medicines using the compound of the present invention. In one embodiment, a compound of formula (I) or (Ia) or a prodrug thereof can be prepared into a galenic dosage form by mixing at ambient temperature, at an appropriate pH and with a physiologically acceptable carrier (i.e., a nontoxic carrier to the recipient at the dosage and concentration employed) in the desired purity. The pH of the preparation depends primarily on the specific use and concentration of the compound, but is generally preferably in the range of about 3 to about 8. In one embodiment, a compound of formula (I) or (Ia) or a prodrug thereof is prepared in an acetate buffer at pH 5. In another embodiment, a compound of formula (I) or (Ia) or a prodrug thereof is sterile. The compound can be stored, for example, as a solid or amorphous composition, as a lyophilized formulation, or as an aqueous solution.

The composition is formulated, dosed, and administered in a manner consistent with good medical practice. Factors considered in this context include the specific condition being treated, the specific mammal being treated, the clinical condition of the individual patient, the cause of the condition, the site of delivery of the agent, the method of administration, the time schedule for administration, and other factors known to practitioners. The "effective amount" of the compound to be administered will be governed by these considerations and is the minimum amount required to activate the TLR7 receptor and result in the production of INF-α and other cytokines, which can be used for, but is not limited to, the treatment or prevention of patients infected with hepatitis B and/or hepatitis C virus.

In one embodiment, the pharmaceutically effective amount of the compound of the invention administered parenterally per dose will be in the range of about 0.1 to 50 mg/kg, or about 0.1 to 30 mg/kg of patient body weight/day, with a typical initial range of 0.3 to 15 mg/kg/day of the compound used. In another embodiment, oral unit dosage forms such as tablets and capsules preferably contain about 20 to about 1000 mg of the compound of the invention.

The compounds of the present invention can be administered by any suitable means, including oral, topical (including buccal and sublingual), rectal, vaginal, transdermal, parenteral, subcutaneous, intraperitoneal, intrapulmonary, intradermal, intrathecal and epidural and intranasal administration, as well as intralesional administration when desired for local treatment. Parenteral infusions include intramuscular, intravenous, intraarterial, intraperitoneal or subcutaneous administration.

The compounds of the present invention can be administered in any convenient administration form, such as tablets, powders, capsules, solutions, dispersions, suspensions, syrups, sprays, suppositories, gels, emulsions, patches, etc. These compositions may contain common components of pharmaceutical preparations, such as diluents, carriers, pH adjusters, sweeteners, fillers and other active substances.

Typical formulations are prepared by mixing the compound of the invention with a carrier or excipient. Suitable carriers and excipients are well known to those skilled in the art and are described in detail in, for example, Ansel, Howard C. et al., Ansel's Pharmaceutical Dosage Forms and Drug Delivery Systems . Philadelphia: Lippincott, Williams & Wilkins, 2004; Gennaro, Alfonso R. et al., Remington: The Science and Practice of Pharmacy . Philadelphia: Lippincott, Williams & Wilkins, 2000; and Rowe, Raymond C. Handbook of Pharmaceutical Excipients . Chicago, Pharmaceutical Press, 2005. The preparation may also contain one or more buffers, stabilizers, surfactants, wetting agents, lubricants, emulsifiers, suspending agents, preservatives, antioxidants, opacifiers, glidants, processing aids, colorants, sweeteners, aromas, flavorings, diluents and other well-known additives in order to give the drug (i.e., the compound of the present invention or its pharmaceutical composition) a beautiful appearance or facilitate the production of the pharmaceutical product (i.e., the drug).

An example of a suitable oral dosage form is a tablet comprising about 20 to 1000 mg of a compound of the invention, about 30 to 90 mg of anhydrous lactose, about 5 to 40 mg of croscarmellose sodium, about 5 to 30 mg of polyvinylpyrrolidone (PVP) K30, and about 1 to 10 mg of magnesium stearate. The powdered ingredients are first mixed together and then mixed with a solution of PVP. The resulting composition can be dried, granulated, mixed with magnesium stearate, and compressed into tablets using conventional equipment. An example of an aerosol formulation can be prepared by dissolving, for example, 20 to 1000 mg of a compound of the invention in a suitable buffer solution, such as a phosphate buffer, and adding a tonicity agent, such as a salt, such as sodium chloride, as needed. The solution can be filtered, for example, using a 0.2 micron filter to remove impurities and contaminants.

Thus, one embodiment includes a pharmaceutical composition comprising a compound of Formula (I) or (Ia) or a prodrug thereof of Formula (II) or (IIa) or a pharmaceutically acceptable salt or enantiomer or diastereomer thereof.

In another embodiment, a pharmaceutical composition comprising a compound of Formula (I) or (Ia) or a prodrug thereof of Formula (II) or (IIa) or a pharmaceutically acceptable salt or enantiomer or diastereomer thereof, and a pharmaceutically acceptable carrier or excipient is included.

Another embodiment includes a pharmaceutical composition for treating hepatitis B virus infection comprising a compound of Formula (I) or (Ia) or a prodrug thereof of Formula (II) or (IIa) or a pharmaceutically acceptable salt or enantiomer or diastereomer thereof.

Indications and treatments

The present invention provides methods for treating or preventing hepatitis B virus infection and/or hepatitis C virus infection in a patient in need thereof.

The present invention also provides methods for introducing a therapeutically effective amount of a compound of formula (I) or (Ia) or a prodrug thereof, or other compounds of the present invention, into a patient's bloodstream for treating and/or preventing hepatitis B virus infection and/or hepatitis C virus infection.

The methods of the present invention are particularly suitable for human patients. Specifically, the methods and dosages of the present invention can be used for, but are not limited to, patients infected with HBV and/or HCV. The methods and dosages of the present invention can also be used for other patients undergoing antiviral therapy. The prophylactic methods of the present invention are particularly suitable for patients at risk of viral infection. These patients include, but are not limited to, healthcare workers, such as doctors, nurses, hospice caregivers; military personnel; teachers; childcare workers; patients traveling to or living abroad, particularly in third world regions, including social aid workers, missionaries, and diplomats. Finally, the methods and compositions described include the treatment of refractory patients or patients who are resistant to treatment, such as patients who are resistant to reverse transcriptase inhibitors, protease inhibitors, etc.

Another embodiment includes a method of treating or preventing hepatitis B virus infection and/or hepatitis C virus infection in a mammal in need of such treatment, comprising administering to the mammal a therapeutically effective amount of a compound of Formula (I) or (Ia) or a prodrug thereof, or an enantiomer, diastereomer, prodrug or pharmaceutically acceptable salt thereof.

Example

The present invention may be more fully understood by reference to the following examples, which, however, should not be construed as limiting the scope of the invention.

abbreviation

ACN: acetonitrile

HATU: 1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridine 3-oxide hexafluorophosphate

DMAP: 4-dimethylaminopyridine

DIPEA: Diisopropylethylamine

p-TsOH: 4-Methylbenzenesulfonic acid

DMSO-d ₆ : deuterated dimethyl sulfoxide

DCM: dichloromethane

FBS: Fetal Bovine Serum

rt: room temperature

HPLC: High Performance Liquid Chromatography

LiAlH(Ot-Bu) ₃ : lithium aluminum tri-tert-butoxyhydride

v/v: volume ratio

SFC: Supercritical Liquid Chromatography

MS(ESI): Mass Spectrometry (Electron Spray Ionization)

BSA: N,O-bis(trimethylsilyl)acetamide

obsd.: measured value

_EC50 : The molar concentration of an agonist that produces 50% of the agonist's maximum possible response

TEA: Triethylamine

TMSCHN ₂ : trimethylsilyldiazomethane

TMSI: Iodotrimethylsilane

CDI: 1,1'-Carbonyldiimidazole

TMSCl: trimethylchlorosilane

NBS: N-bromosuccinimide

General experimental conditions

Intermediates and final compounds were purified by flash chromatography using one of the following instruments: i) Biotage SP1 system with Quad 12/25 cartridge assembly; ii) ISCO combination flash chromatograph. Silica gel brands and pore sizes: i) KP-SIL particle size: 40-60 μm; ii) CAS Registry Number: 63231-67-4, particle size: 47-60 μm; iii) ZCX from Qingdao Haiyang Chemical Co., Ltd., pore size: 200-300 or 300-400.

Intermediates and final compounds were purified by reverse phase column preparative HPLC using either an X Bridge ^™ Perp C ₁₈ (5 μm, OBD ^™ 30×100 mm) column or a SunFire ^™ Perp C ₁₈ (5 μm, OBD ^™ 30×100 mm) column.

LC/MS spectra were obtained using a Waters UPLC-SQD mass spectrometer. Standard LC/MS conditions were as follows (run time 3 minutes):

Acidic conditions: A: 0.1% formic acid and 1% acetonitrile in H ₂ O solution; B: 0.1% formic acid in acetonitrile solution;

Basic conditions: A: 0.05% NH ₃ ·H ₂ O in H ₂ O solution; B: acetonitrile;

Mass Spectrometry (MS): Generally only ions indicating the mass of the parent nucleus are reported, and unless otherwise stated, mass ions quoted are positive mass ions (M+H) ⁺ .

NMR spectra were obtained using a Bruker Avance 400 MHz.

All reactions involving air-sensitive reagents were performed under argon. Unless otherwise stated, reagents were used directly from commercial suppliers without further purification.

Preparation Example

Example 1

Methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetate

Preparation of 2-[2-(Benzoyloxymethyl)-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 1a)

A mixture of benzoyloxyacetaldehyde (1.97 g, 12 mmol) and mercaptosuccinic acid (1.5 g, 10 mmol) was stirred in toluene (50 mL) at 60 ° C for 4 hours in the presence of a catalytic amount of p-TsOH (0.23 g, 1.3 mmol). After the reaction was completed, the mixture was cooled to room temperature and diluted with EtOAc (50 mL), washed with saturated sodium bicarbonate and brine. The organic layer was dried over sodium sulfate, filtered and concentrated to give a crude product, which was purified by column chromatography to give 2.5 g of 2-[2-(benzoyloxymethyl)-5-oxo-1,3-oxathiolane-4-yl]acetic acid (Compound 1a) as a white powder.

Compound 1a: ¹ H NMR (400 MHz, DMSO-d ₆ ) δ ppm: 12.78 (brs, 1H), 7.99 (m, 2H), 7.70 (m, 1H), 7.57 (m, 2H), 5.92 (t, J=4.8 Hz, 1H), 4.53-4.65 (m, 2H), 4.42-4.53 (m, 1H), 2.72-3.06 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 297.

Preparation of [4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1b)

To a solution of 2-[2-(benzoyloxymethyl)-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 1a) (1.5 g, 5.1 mmol) in DCM (20 mL) was added CDI (1.23 g, 7.6 mmol). The mixture was stirred at room temperature for 3 hours, then MeOH (0.62 mL, 15 mmol) was added. The mixture was stirred at room temperature for an additional 16 hours. After completion of the reaction, the reaction mixture was quenched with saturated _NH4Cl and extracted with DCM. The combined organic layers were washed with saturated _NH4Cl and brine, dried over sodium sulfate, filtered, and concentrated to yield the crude product, which was purified by column chromatography to yield 0.83 g of [4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1b) as a yellow oil.

Compound 1b: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 8.05 (m, 2H), 7.62 (m, 1H), 7.48 (m, 2H), 5.74-5.86 (m, 1H), 4.60 (m, 2H), 4.30-4.40 (m, 1H), 3.77 (m, 3H), 2.97-3.24 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 311.

Preparation of [5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1c)

To a solution of [4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1b) (600 mg, 1.9 mmol) in anhydrous THF (10 mL) was added dropwise LiAlH(Ot-Bu) ₃ (1 M in THF, 2.9 mL, 2.9 mmol) at -78°C. After stirring at room temperature for 2 hours, pyridine (0.78 mL, 9.6 mmol), acetic anhydride (0.91 mL, 9.6 mmol), and DMAP (0.71 g, 5.8 mmol) were added. The reaction mixture was stirred at room temperature overnight and then quenched with saturated NH ₄ Cl. The solution was extracted three times with DCM (50 mL). The organic layers were combined, washed with brine, dried over sodium sulfate, filtered and concentrated to give the crude product, which was purified by flash column chromatography to give 0.34 g of [5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1c) as a yellow oil.

Compound 1c: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 8.08 (m, 2H), 7.59 (m, 1H), 7.47 (m, 2H), 6.42-6.73 (m, 1H), 5.65-5.77 (m, 1H), 4.50-4.70 (m, 1H), 4.34-4.42 (m, 1H), 3.90-4.03 (m, 1H), 3.67-3.78 (m, 3H), 2.58-2.91 (m, 2H), 2.06-2.18 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 355.

Preparation of [5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1d)

To a solution of 5-amino-7-hydroxy-3H-thiazolo[4,5-d]pyrimidin-2-one (368 mg, 2.0 mmol) in ACN (15 mL) was added BSA (1.42 g, 7.0 mmol). The mixture was heated at 60 ° C until a clear solution was formed. The solvent was evaporated under reduced pressure. The residue was dissolved in DCM (20 mL). To the above solution was added benzoic acid [5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl ester (Compound 1c) (700 mg, 2.0 mmol) and TMSI (0.61 mL, 4.4 mmol). After stirring at room temperature overnight, the reaction mixture was quenched with saturated NaHCO ₃ solution. The mixture was extracted three times with DCM (100 mL). The combined organic layers were washed with saturated sodium bicarbonate and brine, dried over sodium sulfate, filtered, and concentrated to give a crude product, which was purified by flash silica gel column chromatography to give 0.22 g of light yellow powdered benzoic acid [5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl ester (Compound 1d). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 479.

Preparation of methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetate (Example 1)

To a solution of [5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 1d) (180 mg, 0.38 mmol) in MeOH (10 mL) was added K ₂ CO ₃ (0.21 g, 1.5 mmol) and the mixture was stirred at room temperature. After the reaction was completed, the mixture was neutralized with HOAc to pH 7 and then concentrated to obtain a crude product, which was purified by preparative HPLC to obtain 2 mg of methyl 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-hydroxymethyl)-1,3-oxathiolan-4-yl]acetate (Example 1-P1) and 4 mg of methyl 2-[(cis-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-hydroxymethyl)-1,3-oxathiolan-4-yl]acetate (Example 1-P2) as white powders. The relative configurations of Examples 1-P1 and 1-P2 were determined in a manner similar to that of Example 2.

Example 1-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.96 (d, J=8.5 Hz, 1H), 5.29 (dd, J=5.5, 4.3 Hz, 1H), 4.86 (m, 1H), 3.83 (m, 1H), 3.75 (m, 1H), 3.61 (s, 3H), 2.76 (d, J=7.3 Hz, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 375.

Example 1-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.14 (d, J=7.0 Hz, 1H), 5.78 (dd, J=5.3, 4.0 Hz, 1H), 4.83 (m, 1H), 3.75 (m, 2H), 3.61 (s, 3H), 2.82 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 375.

Example 2

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid

Preparation of 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid (Example 2)

To a solution of crude methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetate (Example 1) (168 mg, 0.45 mmol) in THF (10 mL) was added aqueous LiOH (2 M, 5 mL, 1.0 mmol). The reaction mixture was stirred at room temperature. After the reaction is complete, the mixture is neutralized with HOAc to pH 7 and concentrated to give a crude product, which is purified by preparative HPLC to give 8 mg of 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid (Example 2-P1) and 17 mg of 2-[(cis-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid (Example 2-P2) as a white powder. The relative configuration of the compounds of Example 2-P1 and Example 2-P2 was determined by NOESY.

Example 2-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.96 (d, J=8.5 Hz, 1H), 5.28 (dd, J=5.5, 4.0 Hz, 1H), 4.85 (m, 1H), 3.83 (m, 1H), 3.75 (m, 1H), 2.67 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 361.

Example 2-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.13 (d, J=7.0 Hz, 1H), 5.77 (dd, J=5.5, 4.3 Hz, 1H), 4.83 (m, 1H), 3.75 (m, 2H), 2.77 (m, 1H), 2.66 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 361.

For Example 2-P1, NOESY correlations were observed between C1′-H and C4′-H, and between C1′-H and C6′-H, but no correlation was observed between C2′-H and C4′-H. For Example 2-P2, NOESY correlations were observed between C2′-H and C4′-H, and between C1′-H and C6′-H, but no correlation was observed between C1′-H and C4′-H.

Example 3

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide

Preparation of 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide

To a solution of crude 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]acetic acid (Example 2) (133 mg, 0.37 mol), dimethylamine (0.22 mL, 0.45 mol) and DIPEA (0.3 mL, 1.5 mmol) in DMF (5 mL) was added HATU (214 mg, 0.56 mmol). The reaction mixture was stirred at room temperature for 1 hour, quenched with saturated NH ₄ Cl, and extracted with EtOAc. The combined organic layers were washed with brine, dried over sodium sulfate, filtered and concentrated to give a crude product, which was purified by preparative HPLC to give 6 mg of 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide (Example 3-P1) and 10 mg of 2-[(cis-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide (Example 3-P2) as white powders. The relative configurations of the compounds of Example 3-P1 and Example 3-P2 were determined in a manner similar to Example 2.

Example 3-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.96 (d, J=8.8 Hz, 1H), 5.28 (dd, J=5.3, 4.02 Hz, 1H), 4.95 (m, 1H), 3.79 (m, 2H), 3.03 (s, 3H), 2.88 (m, 1H), 2.84 (s, 3H), 2.76 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 388.

Example 3-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.13 (d, J=7.0 Hz, 1H), 5.76 (t, J=4.6 Hz, 1H), 4.86 (m, 1H), 3.75 (m, 2H), 3.05 (s, 3H), 2.95 (m, 1H), 2.86 (s, 3H), 2.83 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 388.

Example 4

Methyl 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate

Preparation of 2-[(4S)-2-[(1S)-1-benzoyloxypropyl]-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 4a)

A mixture of (1S)-1-formylpropyl benzoate (4.6 g, 24 mmol) (synthesis see: J. Am. Chem. Soc. 2009, 131, 3450-3451), (S)-2-mercaptosuccinic acid (3.59 g, 24 mmol), and p-TsOH (455 mg, 2.4 mmol) in toluene (200 mL) was stirred at 60°C for 4 hours. After completion of the reaction, the mixture was diluted with EtOAc (100 mL), washed with saturated sodium bicarbonate and brine, dried over sodium sulfate, and concentrated. The residue was purified by flash silica gel chromatography (EtOAc/hexane = 1:10 to 1:3 as eluent) to yield 3.9 g of 2-[(4S)-2-[(1S)-1-benzoyloxypropyl]-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 4a) as a brown oil.

Compound 4a: ¹ H NMR (400 MHz, DMSO-d ₆ ) δ ppm: 12.78 (brs, 1H), 7.98 (m, 2H), 7.71 (m, 1H), 7.57 (t, J=7.7 Hz, 2H), 5.81-5.91 (m, 1H), 5.19-5.39 (m, 1H), 4.21-4.50 (m, 1H), 2.63-3.00 (m, 2H), 1.63-1.88 (m, 2H), 0.93 (t, J=7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 325.

Preparation of [(1S)-1-[(4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl]benzoate (Compound 4b)

To a solution of 2-((4S)-2-((S)-1-(benzoyloxy)propyl)-5-oxo-1,3-oxathiolan-4-yl)acetic acid (Compound 4a) (3.6 g, 12 mmol) in Et ₂ O/MeOH (v/v = 4:1, 100 mL) was added TMSCHN ₂ (2 M in hexane, 8.3 mL, 17 mmol) at room temperature. The reaction mixture was then stirred at room temperature for 2 hours, quenched with water (50 mL), and extracted with EtOAc. The combined organic extracts were washed with brine, dried over sodium sulfate, and concentrated. The residue was purified by flash chromatography (EtOAc/hexane = 1:10 to 1:1 as eluent) to give 3.6 g of [(1S)-1-[(4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl] benzoate (Compound 4b) as a cis/trans mixture. Benzoic acid [(1S)-1-[(4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl] ester (compound 4b) (2.1 g, 6.2 mmol) was further separated by SFC to obtain yellow oily [(1S)-1-[(2S,4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl] ester (compound 4b1) 0.87 g and [(1S)-1-[(2R,4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl] ester (compound 4b2) 0.9 g. The absolute configurations of compounds 4b1 and 4b2 were determined by NOESY.

Compound 4b: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 8.05 (m, 2H), 7.66 (m, 1H), 7.52 (m, 2H), 5.81 (m, 1H), 5.26-5.44 (m, 1H), 4.23-4.50 (m, 1H), 3.62- 3.77 (m, 3H), 2.79-3.12 (m, 2H), 1.77-1.99 (m, 2H), 0.99-1.09 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 339.

Compound 4b1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 8.05 (dd, J = 8.3, 1.3 Hz, 2H), 7.67 (m, 1H), 7.53 (m, 2H), 5.80 (dd, J = 4.3, 0.8 Hz, 1H), 5.31 (m, 1H), 4.27 (m, 1H), 3.70 (s, 3H), 3.06-2.92 (m, 2H), 1.91 (m, 2H), 1.03 (t, J = 7.5 Hz, 3H).

Compound 4b2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 8.06 (dd, J = 1.3, 8.3 Hz, 2H), 7.66 (m, 1H), 7.53 (m, 2H), 5.82 (d, J = 4.8 Hz, 1H), 5.39 (td, J = 8.8, 4.4 Hz, 1H), 4.47 (dd, J = 8.5, 4.3 Hz, 1H), 3.73 (s, 3H), 3.07 (dd, J = 17.2, 4.4 Hz, 1H), 2.91-2.80 (m, 1H), 2.00-1.77 (m, 2H), 1.03 (t, J = 7.5 Hz, 3H).

For compound 4b1, NOESY correlations were observed between C2′-H and C5′-H. For compound 4b2, NOESY correlations were observed between C2′-H and C4′-H.

Preparation of [(1S)-1-[(4S)-5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl] benzoate (Compound 4c)

To a solution of [(1S)-1-[(4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl]benzoate (Compound 4b) (3.3 g, 9.8 mmol) in anhydrous THF (60 mL) was added dropwise LiAlH(Ot-Bu) ₃ (1 M in THF, 14.6 mL, 15 mmol) at -78°C. The reaction mixture was warmed to room temperature and stirred at room temperature for 2 hours. Pyridine (3.86 g, 3.9 mL, 49 mmol), acetic anhydride (4.98 g, 4.6 mL, 49 mmol), and DMAP (3.57 g, 29 mmol) were then added. The reaction mixture was stirred at room temperature overnight and then quenched with saturated NH ₄ Cl. The solution was extracted three times with DCM (50 mL). The combined organic layers were washed with brine, dried over sodium sulfate, and concentrated. The residue was purified by flash silica gel chromatography (EtOAc/hexane = 1:10 to 3:1 as eluent) to give 3.7 g of [(1S)-1-[(4S)-5-acetoxy-4-(2-methoxy-2-oxoethyl)-1,3-oxathiolan-2-yl]propyl] benzoate (Compound 4c) as a yellow oil.

Compound 4c: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 8.05 (m, 2H), 7.64 (m, 1H), 7.51 (m, 2H), 6.34-6.50 (m, 1H), 5.42-5.67 (m, 1H), 5.23-5.36 (m, 1H), 3.83-4.16 (m, 1H), 3.64-3.73 (m, 3H), 2.59-2.92 (m, 2H), 2.01-2.38 (m, 3H), 1.57-1.93 (m, 2H), 0.92-1.04 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 383.

Preparation of [(1S)-1-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl]benzoate (Compound 4d)

To a solution of 5-amino-7-hydroxythiazolo[4,5-d]pyrimidin-2(3H)-one (1.4 g, 7.6 mmol) in anhydrous _CH₃CN (50 mL) was added BSA (5.71 g, 28 mmol). The mixture was heated at 60°C until the solution became clear. The solvent was evaporated under reduced pressure. The residue was redissolved in anhydrous DCM (100 mL). To the solution was added [(1S)-1-[(4S)-5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl]benzoate (Compound 4c) (2.9 g, 7.6 mmol) and TMSI (3.34 g, 2.3 mL, 17 mmol). The reaction mixture was stirred at room temperature overnight and then quenched with saturated _NaHCO₃ . The solution was extracted three times with DCM (100 mL) and washed with saturated sodium bicarbonate and brine. The organic layer was dried over sodium sulfate and then concentrated. The residue was purified by flash silica gel chromatography (DCM/MeOH = 20:1 as eluent) to afford 1.7 g of [(1S)-1-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl]benzoate (Compound 4d) as a yellow solid. MS found (ESI ⁺ ) [(M+H) ⁺ ]: 507.

Preparation of methyl 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate (Example 4)

To a solution of [(1S)-1-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl]benzoate (Compound 4d) (0.25 g, 0.49 mmol) in MeOH (10 mL) was added K ₂ CO ₃ (0.13 g, 0.94 mmol). The mixture was stirred at room temperature overnight. After completion of the reaction, the reaction mixture was neutralized with HOAc to pH 7. The mixture was concentrated in vacuo. The residue was purified by preparative HPLC to give 3 mg of methyl 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate (Example 4-P1) and 4 mg of methyl 2-[(2R,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate (Example 4-P2) as white powders. The absolute configurations of Examples 4-P1 and 4-P2 were determined by NOESY.

Example 4-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.94 (d, J = 8.5 Hz, 1H), 5.17 (d, J = 5.3 Hz, 1H), 4.81 (m, 1H), 3.65 (ddd, J = 8.9, 5.1, 3.5 Hz, 1H), 3.60 (s, 3H), 2.76 (d, J = 7.0 Hz, 2H), 1.64 (m, 1H), 1.50 (m, 1H), 1.02 (t, J = 7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 403.

Example 4-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.14 (d, J = 7.0 Hz, 1H), 5.67 (d, J = 5.5 Hz, 1H), 4.79 (q, J = 7.1 Hz, 1H), 3.68 (ddd, J = 8.8, 5.2, 3.8 Hz, 1H), 3.61 (s, 3H), 2.81 (m, 2H), 1.66 (m, 1H), 1.41 (m, 1H), 1.01 (t, J = 7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 403.

For Example 4-P1, NOESY correlations were observed between C2′-H and C5′-H, and between C1′-H and C4′-H. For Example 4-P2, NOESY correlations were observed between C2′-H and C4′-H, but no correlations were observed between C1′-H and C4′-H.

Example 5

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid

Preparation of 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid (Example 5)

To a solution of crude methyl 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetate (Example 4) (400 mg, 1.0 mmol) in THF (10 mL) was added aqueous LiOH (1 M, 5 mL, 5 mmol). The reaction mixture was stirred at room temperature for 2 hours, then neutralized with 1N HCl to pH 7 and concentrated to give a crude product, which was purified by preparative HPLC to give 3 mg of 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid (Example 5-P1) and 4 mg of 2-[(2R,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid (Example 5-P2) as white powders. The absolute configurations of Example 5-P1 and Example 5-P2 were determined by NOESY.

Example 5-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.93 (d, J = 8.5 Hz, 1H), 5.14 (d, J = 5.5 Hz, 1H), 4.82 (m, 1H), 3.65 (m, 1H), 2.63 (m, 2H), 1.64 (m, 1H), 1.49 (m, 1H), 1.02 (t, J = 7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

Example 5-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.13 (d, J = 7.0 Hz, 1H), 5.66 (d, J = 5.5 Hz, 1H), 4.79 (m, 1H), 3.67 (ddd, J = 8.9, 5.3, 3.6 Hz, 1H), 2.75 (m, 1H), 2.66 (m, 1H), 1.68 (m, 1H), 1.42 (m, 1H), 1.01 (t, J = 7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

For Example 5-P1, NOESY correlation was observed between C1′-H and C4′-H, while C2′-H was not correlated with C4′-H. For Example 5-P2, NOESY correlation was observed between C2′-H and C4′-H, while C1′-H was not correlated with C4′-H.

Example 6

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide

Preparation of 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide (Example 6)

To a solution of crude 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]acetic acid (Example 5) (200 mg, 0.51 mmol) in DMF (5 mL) was added methylamine hydrochloride (70 mg, 1.03 mol), DIPEA (0.36 mL, 2.1 mmol), and HATU (294 mg, 0.77 mmol). The reaction was stirred at room temperature for 2 hours, then quenched with saturated _NH4Cl and extracted with EtOAc. The organic layer was concentrated to obtain a crude product, which was further purified by preparative HPLC to obtain 2 mg of 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide (Example 6-P1) and 5 mg of 2-[(2R,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N-methyl-acetamide (Example 6-P2) as white powders. The absolute configuration was determined in a manner similar to that of Example 5.

Example 6-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.91 (d, J = 8.8 Hz, 1H), 5.15 (d, J = 5.3 Hz, 1H), 4.84 (m, 1H), 3.65 (m, 1H), 2.62 (s, 3H), 2.55 (d, J = 7.3 Hz, 2H), 1.64 (m, 1H), 1.50 (m, 1H), 1.02 (t, J = 7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 402.

Example 6-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.10 (d, J=7.3 Hz, 1H), 5.69 (d, J=5.5 Hz, 1H), 4.83 (m, 1H), 3.68 (m, 1H), 2.64 (s, 3H), 2.57 (m, 2H), 1.68 (m, 1H), 1.42 (m, 1H), 1.01 (t, J=7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 402.

Example 7

2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide

Preparation of 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide (7)

The title compound was prepared in a similar manner to Example 6 by replacing methylamine hydrochloride with dimethylamine. Example 7 was further purified by preparative HPLC to give 4 mg of 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide (Example 7-P1) and 9 mg of 2-[(2R,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxathiolan-4-yl]-N,N-dimethyl-acetamide (Example 7-P2) as white powders. The absolute configurations of Example 7-P1 and Example 7-P2 were determined in a similar manner to Example 5.

Example 7-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.93 (d, J=8.5 Hz, 1H), 5.14 (d, J=5.3 Hz, 1H), 4.91 (m, 1H), 3.66 (m, 1H), 3.04 (s, 3H), 2.89 (m, 1H), 2.84 (s, 3H), 2.77 (m, 1H), 1.65 (m, 1H), 1.50 (m, 1H), 1.02 (t, J=7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 416.

Example 7-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.14 (d, J = 7.0 Hz, 1H), 5.65 (d, J = 5.0 Hz, 1H), 4.84 (m, 1H), 3.69 (ddd, J = 8.8, 5.0, 3.8 Hz, 1H), 3.06 (s, 3H), 2.94 (m, 1H), 2.82 (m, 4H), 1.67 (m, 1H), 1.41 (m, 1H), 1.01 (t, J = 7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 416.

Example 8

5-Amino-3-[(4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxoethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione

Preparation of 5-amino-3-[(4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione (Compound 8)

The title compound was prepared in a manner similar to Example 6 by replacing methylamine hydrochloride with morpholine. Example 8 was further purified by preparative HPLC to give 4 mg of 5-amino-3-[(2S,4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione (Example 8-P1) and 10 mg of 5-amino-3-[(2R,4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxathiolan-5-yl]-6H-thiazolo[4,5-d]pyrimidine-2,7-dione (Example 8-P2) as white powders. The absolute configurations of Example 8-P1 and Example 8-P2 were determined in a manner similar to Example 5.

Example 8-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.93 (d, J=8.5 Hz, 1H), 5.14 (d, J=5.3 Hz, 1H), 4.94 (m, 1H), 3.65 (m, 3H), 3.59 (m, 2H), 3.48 (m, 4H), 2.84 (m, 2H), 1.65 (m, 1H), 1.50 (m, 1H), 1.02 (t, J=7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 458.

Example 8-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.13 (m, 1H), 5.65 (d, J = 5.0 Hz, 1H), 4.93 (m, 1H), 3.68 (m, 3H), 3.60 (m, 2H), 3.52 (m, 2H), 3.48 (m, 2H), 2.92 (m, 1H), 2.86 (m, 1H), 1.67 (m, 1H), 1.41 (m, 1H), 1.01 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 458.

Example 9

Methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetate

Preparation of [(1S)-1-methyl-2-oxo-ethyl]benzoate (Compound 9a)

A mixture of propanal (5.0 g, 86 mmol), [diphenyl-[(2S)-pyrrolidin-2-yl]methoxy]-trimethylsilane (2.8 g, 8.6 mmol), and hydroquinone (948 mg, 8.6 mmol) in THF (200 mL) was stirred at 0°C. Benzyl peroxide (22.9 g, 95 mmol) was then added to the mixture. After stirring at 0°C to room temperature for 4 hours, the reaction mixture was poured into 1N aqueous HCl (200 mL) and extracted with EtOAc, washed with saturated sodium bicarbonate and brine, dried over sodium sulfate, and concentrated. The residue was purified by flash silica gel chromatography (EtOAc/hexane = 1:10 to 1:3 as eluent) to yield 4.5 g of [(1S)-1-methyl-2-oxo-ethyl] benzoate (Compound 9a) as a yellow oil.

Compound 9a: ¹ H NMR (400 MHz, DMSO-d ₆ ) δ ppm: 9.64 (m, 1H), 8.03 (m, 2H), 7.71 (m, 1H), 7.62 (m, 2H), 4.99 (m, 1H), 1.48 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 179.

Preparation of 2-[2-[(1S)-1-benzoyloxyethyl]-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 9b)

A mixture of (1S)-1-methyl-2-oxoethyl benzoate (Compound 9a) (3.0 g, 17 mmol), 2-mercaptosuccinic acid (2.53 g, 17 mmol), and p-TsOH (320 mg, 1.7 mmol) in toluene (150 mL) was stirred at 60°C for 4 hours. After completion of the reaction, the reaction mixture was diluted with EtOAc (50 mL), washed with saturated sodium bicarbonate and brine, dried over sodium sulfate, and concentrated. The residue was purified by flash silica gel chromatography (EtOAc/hexane = 1:10 to 1:3 as eluent) to give 4.7 g of 2-[2-[(1S)-1-benzoyloxyethyl]-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 9b) as a yellow oil.

Compound 9b: ¹ H NMR (400 MHz, DMSO-d ₆ ) δ ppm: 12.76 (brs, 1H), 7.95 (m, 2H), 7.70 (m, 1H), 7.56 (t, J=7.7, 2H), 5.78-5.86 (m, 1H), 5.24-5.40 (m, 1H), 4.28-4.54 (m, 1H), 2.57-3.02 (m, 2H), 1.33-1.42 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 311.

Preparation of [(1S)-1-[4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9c)

To a solution of 2-[2-[(1S)-1-benzoyloxyethyl]-5-oxo-1,3-oxathiolan-4-yl]acetic acid (Compound 9b) (1.7 g, 5.5 mmol) in Et ₂ O/MeOH (v/v = 4:1, 50 mL) was added TMSCHN ₂ (2M in hexane, 4.1 mL, 8.2 mmol) at room temperature. The reaction mixture was stirred at room temperature for 2 hours, then quenched with water (50 mL) and extracted with EtOAc. The combined organic extracts were washed with brine, dried over sodium sulfate, and concentrated. The residue was purified by flash silica gel chromatography (EtOAc/hexane = 1:10 to 1:1 as eluent) to give 1.5 g of yellow oily [(1S)-1-[4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9c).

Compound 9c: ¹ H NMR (400 MHz, DMSO-d ₆ ) δ ppm: 7.96 (m, 2H), 7.71 (m, 1H), 7.57 (t, J=7.7 Hz, 2H), 5.77-5.90 (m, 1H), 5.21-5.44 (m, 1H), 4.34- 4.59 (m, 1H), 3.55-3.67 (m, 3H), 2.74-3.09 (m, 2H), 1.38 (q, J=6.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 325.

Preparation of [(1S)-1-[5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9d)

To a solution of [(1S)-1-[4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9c) (1.5 g, 4.6 mmol) in anhydrous THF (60 mL) was added dropwise LiAlH(Ot-Bu) ₃ (1 M in THF, 6.9 mL, 6.9 mmol) at -78°C. The reaction mixture was warmed to room temperature and stirred at room temperature for 2 hours. Pyridine (1.87 mL, 23 mmol), acetic anhydride (2.2 mL, 23 mmol), and DMAP (1.69 g, 14 mmol) were then added. The reaction mixture was stirred at room temperature overnight and then quenched with saturated NH ₄ Cl. The solution was extracted three times with DCM (50 mL). The combined organic layers were washed with brine, dried over sodium sulfate, and concentrated. The residue was purified by flash silica gel chromatography (EtOAc/hexane = 1:10 to 1:3 as eluent) to give 1.1 g of [(1S)-1-[5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]ethyl] benzoate (Compound 9d) as a yellow oil.

Compound 9d: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 8.03 (m, 2H), 7.63 (m, 1H), 7.50 (m, 2H), 6.36-6.54 (m, 1H), 5.43-5.60 (m, 1H), 5.22-5.42 (m, 1H), 3.85-4.16 (m, 1H), 3.67-3.75 (m, 3H), 2.58-2.95 (m, 2H), 1.94-2.15 (m, 3H), 1.29-1.47 (m, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 369.

Preparation of [(1S)-1-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9e)

To a solution of 5-amino-7-hydroxythiazolo[4,5-d]pyrimidin-2(3H)-one (550 mg, 3.0 mmol) in anhydrous ACN (50 mL) was added BSA (2.7 mL, 11 mmol). The mixture was heated at 60°C until the solution became clear. The solvent was removed and the residue was redissolved in anhydrous DCM (100 mL). To the solution was added [(1S)-1-[5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9d) (1.1 g, 3.0 mmol) and TMSI (0.91 mL, 6.6 mmol). The reaction mixture was stirred at room temperature overnight and then quenched with saturated _NaHCO₃ . The solution was extracted three times with DCM (100 mL) and washed with saturated sodium bicarbonate and brine. The organic layer was dried over sodium sulfate and concentrated. The residue was purified by flash silica gel chromatography (DCM/methanol = 20:1 as eluent) to afford 600 mg of [(1S)-1-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]ethyl]benzoate (Compound 9e) as a yellow solid. MS found (ESI ⁺ ) [(M+H) ⁺ ]: 493.

Preparation of methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetate (Example 9)

To a solution of [(1S)-1-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]ethyl] benzoate (Compound 9e) (0.6 g, 1.2 mmol) in MeOH (10 mL) _was added _K2CO3 (253 mg, 1.8 mmol). After stirring at room temperature overnight, the reaction mixture was adjusted to pH 7 with 1N aqueous HCl solution and then concentrated to give a crude product, which was further purified by preparative HPLC to give Example 9-P1 (trans-1′, 2′-diastereomer 1) 8 mg, Example 9-P2 (trans-1′, 2′-diastereomer 2) 5 mg, Example 9-P3 (trans-1′, 2′-diastereomer 3) 2 mg and Example 9-P4 (trans-1′, 2′-diastereomer 4) 2.5 mg as white powders.

Example 9-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.14 (d, J = 7.0 Hz, 1H), 5.62 (d, J = 5.3 Hz, 1H), 4.80 (q, J = 7.3 Hz, 1H), 3.92 (m, 1H), 3.61 (s, 3H), 2.82 (m, 2H), 1.23 (d, J = 6.3 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

Example 9-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.14 (d, J = 7.0 Hz, 1H), 5.60 (d, J = 6.0 Hz, 1H), 4.83 (q, J = 7.3 Hz, 1H), 3.89 (quin, J = 6.3 Hz, 1H), 3.61 (s, 3H), 2.81 (m, 2H), 1.21 (d, J = 6.5 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

Example 9-P3: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.94 (d, J = 8.5 Hz, 1H), 5.11 (d, J = 5.8 Hz, 1H), 4.83 (m, 1H), 3.98 (m, 1H), 3.61 (s, 3H), 2.76 (d, J = 7.3 Hz, 2H), 1.23 (d, J = 6.3 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

Example 9-P4: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.95 (d, J = 8.5 Hz, 1H), 5.14 (d, J = 4.3 Hz, 1H), 4.75 (m, 1H), 4.02 (dd, J = 6.4, 4.1 Hz, 1H), 3.60 (s, 3H), 2.75 (d, J = 7.0 Hz, 2H), 1.21 (d, J = 6.5 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

Example 10

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetic acid

Preparation of 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetic acid (Example 10)

To a solution of a crude mixture of methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxathiolan-4-yl]acetate (Example 9, 280 mg, 0.72 mmol) in THF (10 mL) was added aqueous LiOH (1 M, 5 mL, 5.0 mmol). After stirring at room temperature for 2 hours, the reaction mixture was adjusted to pH 6-7 with aqueous HCl and then concentrated. The residue was purified by preparative HPLC to give Example 10-P1 (trans-1′,2′-diastereomer 1) 23 mg, Example 10-P2 (trans-1′,2′-diastereomer 2) 20 mg, Example 10-P3 (trans-1′,2′-diastereomer 3) 9 mg, and Example 10-P4 (trans-1′,2′-diastereomer 4) 9 mg as white powders.

Example 10-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.12 (d, J = 7.0 Hz, 1H), 5.57 (d, J = 6.3 Hz, 1H), 4.83 (m, 1H), 3.88 (quin, J = 6.3 Hz, 1H), 2.73 (m, 1H), 2.61 (m, 1H), 1.20 (d, J = 6.3 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 375.

Example 10-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.13 (d, J = 7.0 Hz, 1H), 5.60 (d, J = 5.0 Hz, 1H), 4.80 (m, 1H), 3.91 (m, 1H), 2.74 (m, 1H), 2.65 (m, 1H), 1.24 (d, J = 6.5 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 375.

Example 10-P3: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.94 (d, J = 8.5 Hz, 1H), 5.10 (d, J = 5.8 Hz, 1H), 4.83 (m, 1H), 3.97 (quin, J = 6.3 Hz, 1H), 2.68 (m, 2H), 1.23 (d, J = 6.3 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 375.

Example 10-P4: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.95 (d, J = 8.8 Hz, 1H), 5.13 (d, J = 4.3 Hz, 1H), 4.74 (m, 1H), 4.02 (m, 1H), 2.67 (m, 2H), 1.21 (d, J = 6.3 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 375.

Example 11

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypentyl]-1,3-oxathiolan-4-yl]acetic acid

Preparation of 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypentyl]-1,3-oxathiolan-4-yl]acetic acid (Example 11)

The title compound was prepared in a manner similar to Example 10 by replacing propionaldehyde with hexanal. Example 11 was further purified by preparative HPLC to give Example 11-P1 (trans-1′,2′-diastereomer 1) (13 mg), Example 11-P2 (trans-1′,2′-diastereomer 2) (21 mg), Example 11-P3 (trans-1′,2′-diastereomer 3) (10 mg), and Example 11-P4 (trans-1′,2′-diastereomer 4) (18 mg) as white powders.

Example 11-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.10 (d, J = 7.0 Hz, 1H), 5.61 (d, J = 6.3 Hz, 1H), 4.84 (m, 1H), 3.66 (m, 1H), 2.65 (dd, J = 15.1, 5.8 Hz, 1H), 2.48 (dd, J = 15.3, 9.3 Hz, 1H), 1.50 (m, 3H), 1.39 (m, 3H), 0.94 (t, J = 7.2 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 417.

Example 11-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.10 (d, J = 7.3 Hz, 1H), 5.64 (d, J = 5.3 Hz, 1H), 4.80 (dt, J = 8.8, 6.5 Hz, 1H), 3.73 (m, 1H), 2.64 (dd, J = 14.9, 5.6 Hz, 1H), 2.47 (dd, J = 14.8, 9.0 Hz, 1H), 1.65 (m, 1H), 1.51 (m, 1H), 1.38 (m, 4H), 0.94 (t, J = 7.2 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 417.

Example 11-P3: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.90 (d, J = 8.8 Hz, 1H), 5.09 (d, J = 5.8 Hz, 1H), 4.83 (m, 1H), 3.72 (m, 1H), 2.58 (m, 1H), 2.45 (dd, J = 15.6, 9.3 Hz, 1H), 1.59 (m, 1H), 1.51 (m, 1H), 1.38 (m, 4H), 0.94 (t, J = 7.2 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 417.

Example 11-P4: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.91 (d, J = 8.8 Hz, 1H), 5.14 (d, J = 4.3 Hz, 1H), 4.75 (td, J = 9.0, 5.1 Hz, 1H), 3.85 (m, 1H), 2.55 (m, 1H), 2.41 (dd, J = 15.1, 9.0 Hz, 1H), 1.46 (m, 6H), 0.94 (t, J = 7.2 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 417.

Example 12

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxybut-3-enyl]-1,3-oxathiolan-4-yl]acetic acid

Preparation of 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxybut-3-enyl]-1,3-oxathiolan-4-yl]acetic acid (12)

The title compound was prepared in a manner similar to Example 10 by replacing propionaldehyde with 4-methylhex-5-enal. Example 12 was further purified by preparative HPLC to give Example 12-P1 (trans-1′,2′-diastereomer 1) (23 mg), Example 12-P2 (trans-1′,2′-diastereomer 2) (22 mg), Example 12-P3 (trans-1′,2′-diastereomer 3) (16 mg), and Example 12-P4 (trans-1′,2′-diastereomer 4) (28 mg) as white powders.

Example 12-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.13 (d, J = 6.8 Hz, 1H), 5.91 (ddt, J = 17.0, 10.1, 7.0 Hz, 1H), 5.65 (d, J = 5.5 Hz, 1H), 5.10 (m, 2H), 4.83 (m, 1H), 3.74 (m, 1H), 2.73 (m, 1H), 2.63 (m, 1H), 2.31 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 12-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.11 (d, J = 7.0 Hz, 1H), 5.90 (ddt, J = 17.2, 10.1, 6.9 Hz, 1H), 5.65 (d, J = 5.5 Hz, 1H), 5.10 (m, 2H), 4.80 (m, 1H), 3.78 (m, 1H), 2.64 (dd, J = 14.7, 5.6 Hz, 1H), 2.44 (m, 2H), 2.22 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 12-P3: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.93 (m, 2H), 5.10 (m, 3H), 4.83 (m, 1H), 3.81 (m, 1H), 2.56 (m, 1H), 2.42 (m, 2H), 2.30 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 12-P4: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.89 (m, 2H), 5.17 (d, J=4.3 Hz, 1H), 5.04-5.16 (m, 2H), 4.75 (m, 1H), 3.94 (m, 1H), 2.56 (m, 2H), 2.31 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 13

Methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetate

Preparation of methyl 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetate (Example 13)

The title compound was prepared in a manner similar to Example 9 by replacing propionaldehyde with 2-cyclopropylacetaldehyde. Example 13 was further purified by preparative HPLC to give Example 13-P1 (trans-1′,2′-diastereomer 1) (11 mg), Example 13-P2 (trans-1′,2′-diastereomer 2) (8 mg), Example 13-P3 (trans-1′,2′-diastereomer 3) (7 mg), and Example 13-P4 (trans-1′,2′-diastereomer 4) (6 mg) as white powders.

Example 13-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.17 (d, J = 7.0 Hz, 1H), 5.76 (d, J = 4.8 Hz, 1H), 4.80 (q, J = 7.0 Hz, 1H), 3.61 (s, 3H), 3.27 (dd, J = 7.5, 4.8 Hz, 1H), 2.83 (dd, J = 7.3, 1.0 Hz, 2H), 0.90 (m, 1H), 0.52 (m, 2H), 0.39 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 415.

Example 13-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.15 (d, J=7.0 Hz, 1H), 5.77 (d, J=6.3 Hz, 1H), 4.83 (m, 1H), 3.61 (s, 3H), 3.02 (dd, J=8.5, 6.3 Hz, 1H), 2.81 (m, 2H), 0.98 (m, 1H), 0.56 (m, 2H), 0.42 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 415.

Example 13-P3: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.95 (d, J = 8.3 Hz, 1H), 5.26 (d, J = 5.5 Hz, 1H), 4.83 (m, 1H), 3.61 (s, 3H), 3.15 (dd, J = 8.0, 5.5 Hz, 1H), 2.78 (d, J = 7.0 Hz, 2H), 0.96 (m, 1H), 0.54 (m, 2H), 0.46 (m, 1H), 0.39 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 415.

Example 13-P4: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.96 (d, J = 8.5 Hz, 1H), 5.33 (d, J = 4.0 Hz, 1H), 4.74 (m, 1H), 3.60 (s, 3H), 3.27 (dd, J = 8.0, 3.8 Hz, 1H), 2.76 (d, J = 7.0 Hz, 2H), 0.92 (m, 1H), 0.52 (m, 2H), 0.42 (m, 1H), 0.35 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 415.

Example 14

2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetic acid

Preparation of 2-[5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxathiolan-4-yl]acetic acid (Example 14)

The title compound was prepared in a manner similar to Example 10 by replacing propionaldehyde with 2-cyclopropylacetaldehyde. Example 14 was further purified by preparative HPLC to give Example 14-P1 (trans-1′,2′-diastereomer 1) (49 mg), Example 14-P2 (trans-1′,2′-diastereomer 2) (38 mg), Example 14-P3 (trans-1′,2′-diastereomer 3) (12 mg), and Example 14-P4 (trans-1′,2′-diastereomer 4) (15 mg) as white powders.

Example 14-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.16 (d, J = 7.0 Hz, 1H), 5.75 (d, J = 6.3 Hz, 1H), 4.83 (m, 1H), 3.02 (dd, J = 8.5, 6.3 Hz, 1H), 2.75 (m, 2H), 0.99 (m, 1H), 0.56 (m, 2H), 0.41 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 14-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.18 (d, J = 7.0 Hz, 1H), 5.75 (d, J = 4.8 Hz, 1H), 4.80 (q, J = 7.1 Hz, 1H), 3.27 (dd, J = 7.5, 4.8 Hz, 1H), 2.77 (m, 2H), 0.90 (m, 1H), 0.52 (m, 2H), 0.39 (m, 2H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 14-P3: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.95 (d, J = 8.3 Hz, 1H), 5.26 (d, J = 5.8 Hz, 1H), 4.82 (m, 1H), 3.15 (dd, J = 8.0, 5.8 Hz, 1H), 2.71 (m, 2H), 0.96 (m, 1H), 0.53 (m, 2H), 0.46 (m, 1H), 0.40 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 14-P4: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 5.97 (d, J = 8.5 Hz, 1H), 5.33 (d, J = 4.0 Hz, 1H), 4.73 (m, 1H), 3.27 (dd, J = 8.0, 3.8 Hz, 1H), 2.71 (d, J = 6.8 Hz, 2H), 0.93 (m, 1H), 0.53 (m, 2H), 0.43 (m, 1H), 0.35 (m, 1H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 401.

Example 15

Benzoic acid [(1S)-1-[(2S,4S,5R)-5-(5-amino-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl] ester

Preparation of [(1S)-1-[(2S,4S,5R)-5-(5-amino-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl]benzoate (Example 15)

In a manner similar to that for [(1S)-1-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl] benzoate (compound 4d), a novel 5-amino-3H-thiazolo[4,5-d]pyrimidin-2-one- was prepared by replacing [(1S)-1-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]propyl] benzoate (compound 4b1) with [(1S)-1-[(2S,4S)-4-(2-methoxy-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]propyl] benzoate (compound 4b2) with [(1S)-1-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-one] [0146] The title compound was prepared by reacting 1,3-oxathiolan-2-yl]propyl] ester (Compound 4b) and 5-amino-3,7a-dihydrothiazolo[4,5-d]pyrimidine-2,7-dione to give 400 mg of a white powder.

Example 15: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 8.22 (s, 1H), 8.08 (m, 2H), 7.63 (m, 1H), 7.50 (m, 2H), 6.07 (d, J=8.0 Hz, 1H), 5.55 (d, J=4.8 Hz, 1H), 5.33 (dt, J=8.8, 4.4 Hz, 1H), 4.95 (q, J=7.3 Hz, 1H), 3.55 (s, 3H), 2.79 (m, 2H), 1.93 (m, 2H), 1.00 (t, J=7.4 Hz, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 491.

Example 16

2-[5-(5-amino-7-hydroxy-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-2-methyl-propionic acid

Preparation of dimethyl 2,2-dimethylsuccinate (Compound 16a)

To a solution of 2,2-dimethylsuccinic acid (15.0 g, 0.10 mol) in MeOH (200 mL) was added acetyl chloride (7.1 mL, 0.10 mol) at 0°C. The reaction mixture was stirred at room temperature overnight. The solvent was evaporated under reduced pressure to yield 18.0 g of crude dimethyl 2,2-dimethylsuccinate (Compound 16a) as a colorless oil.

Compound 16a: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 3.72 (s, 3H), 3.68 (s, 3H), 2.62 (s, 2H), 1.29 (s, 6H).

Preparation of 3-bromo-2,2-dimethyl-succinic acid dimethyl ester (Compound 16b)

Under an argon atmosphere, to a solution of diisopropylamine (8.3 mL, 59 mmol) in THF (200 mL) was added n-BuLi (1.6 M in hexane, 37 mL, 59 mmol) at -78°C. After stirring at -78°C for 30 minutes, a solution of dimethyl 2,2-dimethylsuccinate (Compound 16a) (8.0 g, 45 mmol) in THF (50 mL) was added dropwise. Stirring was continued for 30 minutes, followed by the dropwise addition of TMSCl (10.4 mL, 82 mmol). The reaction mixture was stirred at -78°C for another 30 minutes, followed by the addition of NBS (9.7 g, 54 mmol). The reaction mixture was stirred at -78°C for another 2 hours, then quenched with saturated _NH₄Cl . The reaction mixture was extracted three times with EtOAc (100 mL). The combined organic layers were washed with saturated NH ₄ Cl, H ₂ O, and brine, dried over sodium sulfate, filtered, and concentrated to afford 11.0 g of crude 3-bromo-2,2-dimethyl-succinic acid dimethyl ester (Compound 16b) as a yellow oil.

Compound 16b: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 4.74 (s, 1H), 3.79 (s, 3H), 3.74 (s, 3H), 1.44 (s, 3H), 1.42 (s, 3H).

Preparation of 3-acetylthio-2,2-dimethyl-succinic acid dimethyl ester (Compound 16c)

To a solution of 3-bromo-2,2-dimethyl-succinic acid dimethyl ester (Compound 16b) (11.0 g, 62 mmol) in DMF (100 mL) was added potassium thioacetate (8.54 g, 75 mmol). The reaction mixture was stirred at 60°C for 16 hours. After cooling to room temperature, the reaction was quenched with saturated _NH4Cl and then diluted with EtOAc (300 mL). The organic layer was washed with saturated _NH4Cl , _H2O , and brine, dried over sodium sulfate, filtered, and concentrated to afford 11.0 g of 3-acetylthio-2,2-dimethyl-succinic acid dimethyl ester (Compound 16c) as a brown oil.

Compound 16c: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 4.66 (s, 1H), 3.71 (s, 3H), 3.70 (s, 3H), 2.40 (s, 3H), 1.31 (s, 3H), 1.27 (s, 3H).

Preparation of 2,2-dimethyl-3-mercapto-succinic acid (Compound 16d)

3-Acetylthio-2,2-dimethyl-succinic acid dimethyl ester (Compound 16c) (5.0 g, 20 mmol) was dissolved in 6N HCl/dioxane (v/v = 1:1, 40 mL). The reaction mixture was heated at 90°C for 16 hours, and then the solvent was evaporated under reduced pressure to yield 4.5 g of crude 2,2-dimethyl-3-mercapto-succinic acid (Compound 16d) as a brown oil.

Compound 16d: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 3.76 (d, J=7.0 Hz, 1H), 1.43 (s, 3H), 1.41 (s, 3H).

Preparation of 2-[2-(Benzoyloxymethyl)-5-oxo-1,3-oxathiolan-4-yl]-2-methyl-propionic acid (16e)

A mixture of benzoyloxyacetaldehyde (3.4 g, 20 mmol) and 2,2-dimethyl-3-mercapto-butanedioic acid (compound 16d) (3.6 g, 20 mmol) was stirred in toluene (50 mL) at 60 ° C for 4 hours in the presence of a catalytic amount of p-TsOH (300 mg, 1.7 mmol). After the reaction was completed, the mixture was cooled to room temperature and diluted with EtOAc (100 mL), washed with saturated sodium bicarbonate and brine. The organic layer was dried over sodium sulfate, filtered and concentrated to give a crude product, which was purified by column chromatography to give 4.0 g of colorless oily 2-[2-(benzoyloxymethyl)-5-oxo-1,3-oxathiolane-4-yl]-2-methyl-propionic acid (compound 16e).

Compound 16e: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 8.08 (m, 2H), 7.62 (m, 1H), 7.49 (m, 2H), 5.72 (m, 1H), 4.58 (m, 3H), 1.39-1.49 (m, 6H).

Preparation of [4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]methyl benzoate (Compound 16f)

To a solution of 2-[2-(benzoyloxymethyl)-5-oxo-1,3-oxathiolan-4-yl]-2-methyl-propionic acid (Compound 16e) (1.8 g, 5.5 mmol) in DMF (30 mL) was added CDI (1.8 g, 11 mmol) and a catalytic amount of DMAP (180 mg, 1.5 mmol). The mixture was stirred at 55°C for 1.5 hours, followed by the addition of MeOH (0.88 mL, 22 mmol). The mixture was stirred at 55°C for 3 hours. Upon completion of the reaction, the mixture was quenched with saturated _NH₄Cl and extracted with EtOAc. The combined organic layers were washed with saturated _NH4Cl , _H2O and brine, dried over sodium sulfate, filtered and concentrated to give the crude product, which was purified by column chromatography to give 1.0 g of [4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]methyl benzoate (Compound 16f) as a colorless oil.

Compound 16f: ¹ H NMR (400 MHz, CDCl ₃ ) δ ppm: 8.07 (m, 2H), 7.61 (m, 1H), 7.49 (m, 2H), 5.71 (t, J=5.3 Hz, 1H), 4.51-4.61 (m, 3H), 3.77 (m, 3H), 1.36-1.45 ppm (m, 6H).

Preparation of [5-acetoxy-4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 16g)

To a solution of [4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-5-oxo-1,3-oxathiolan-2-yl]methyl benzoate (Compound 16f) (600 mg, 1.8 mmol) in anhydrous THF (10 mL) was added dropwise LiAlH(Ot-Bu) ( ₁ M in THF, 2.7 mL, 2.7 mmol) at -78°C. After stirring at room temperature for 2 hours, pyridine (0.7 mL, 8.7 mmol), acetic anhydride (0.85 mL, 8.7 mmol), and DMAP (0.66 g, 5.1 mmol) were added. The reaction mixture was stirred at room temperature for 5 hours and then quenched with saturated _NH4Cl . The solution was extracted three times with DCM (30 mL). The organic layers were combined, washed with brine, dried over sodium sulfate, filtered, and concentrated to give a crude product, which was purified by flash column chromatography to give 630 mg of benzoic acid [5-acetoxy-4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl ester (Compound 16g) as a yellow oil. MS found (ESI ⁺ ) [(M+H) ⁺ ]: 383.

Preparation of [5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 16h)

To a suspension of 5-amino-7-hydroxy-3H-thiazolo[4,5-d]pyrimidin-2-one (470 mg, 2.6 mmol) in ACN (20 mL) was added BSA (1.82 g, 2.2 mL, 8.9 mmol). The mixture was stirred at 70°C under an argon atmosphere for 0.5 h to form a clear solution. The solution was concentrated under reduced pressure to form a white solid, which was dissolved in DCM (20 mL). Benzoic acid [5-acetoxy-4-(2-methoxy-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl ester (Compound 16g) (650 mg, 1.7 mmol) and TMSI (680 mg, 472 μL, 3.4 mmol) were added to the DCM solution; the reaction mixture was then stirred at room temperature for 14 h. After completion of the reaction, the mixture was concentrated and the residue was partitioned between EtOAc (50 mL) and saturated _NaHCO₃ solution (15 mL). The organic layer was separated and the aqueous phase was extracted twice with EtOAc (25 mL). The combined organic layers were washed with brine and dried over NaSO ₄ , filtered and concentrated to give 860 mg of crude benzoic acid [5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-1,3-oxathiolane-2-yl]methyl ester (Compound 16h). MS measured value (ESI ⁺ )[(M+H) ⁺ ]: 507. Preparation of 2-[5-(5-amino-7-hydroxy-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolane-4-yl]-2-methyl-propionic acid (Example 16)

To a solution of [5-(5-amino-2,7-dioxo-6H-thiazolo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-1,1-dimethyl-2-oxo-ethyl)-1,3-oxathiolan-2-yl]methyl benzoate (Compound 16h) (400 mg, 790 μmol) in THF (10 mL) was added a solution of LiOH (227 mg, 9.5 mmol) in water (10 mL). The mixture was then stirred at room temperature overnight. After completion of the reaction, the mixture was adjusted to pH 7 with HOAc. The mixture was concentrated and purified by preparative HPLC to give 12 mg of 2-[(cis-2,4-trans-4,5)-5-(5-amino-7-hydroxy-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-2-methyl-propionic acid (Example 16-P1, diastereomer 1) and 8 mg of 2-[(trans-2,4-trans-4,5)-5-(5-amino-7-hydroxy-2-oxo-thiazolo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxathiolan-4-yl]-2-methyl-propionic acid (Example 16-P2, diastereomer 2) as white powders. The relative configurations of Examples 16-P1 and 16-P2 were determined by NOESY.

Example 16-P1: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.28 (d, J=7.5 Hz, 1H), 5.22 (m, 1H), 5.00 (d, J=7.8 Hz, 1H), 3.83 (m, 1H), 3.74 (m, 1H), 1.31 (m, 6H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

Example 16-P2: ¹ H NMR (400 MHz, CD ₃ OD) δ ppm: 6.42 (d, J=5.5 Hz, 1H), 5.76 (t, J=4.8 Hz, 1H), 4.96 (m, 1H), 3.77 (m, 1H), 3.70 (m, 1H), 1.31 (s, 3H), 1.29 (s, 3H). MS found (ESI ⁺ ) [(M+H) ⁺ ]: 389.

For Example 16-P1, NOESY correlation was observed between C4′-H and C1′-H, and correlation was observed between C4′-H, C6′-H, and C6″-H. For Example 16-P2, correlation was observed between C4′-H and C2′-H, and correlation was observed between C5′-H and C1′-H.

Example 17

HEK293-Blue-hTLR-7 cell assay:

The stable HEK293-Blue-hTLR-7 cell line was purchased from InvivoGen (Catalog No.: hkb-htlr7, San Diego, California, USA). These cells were designed to study human TLR7 stimulation by monitoring NF-κB activation. The SEAP (secreted embryonic alkaline phosphatase) reporter gene was placed under the control of a minimal IFN-β promoter fused to five NF-κB and AP-1 binding sites. SEAP is induced by activating NF-κB and AP-1 in HEK-Blue hTLR7 cells upon stimulation with TLR7 ligands. Therefore, upon stimulation of human TLR7, the NF-κB promoter regulates reporter gene expression. SEAP reporter gene activity in cell culture supernatants was measured at a wavelength of 640 nm using the QUANTI-Blue ^™ kit (Catalog No.: rep-qb1, Invivogen, San Diego, California, USA). This assay medium changes color from purple to blue in the presence of alkaline phosphatase.

HEK293-Blue-hTLR7 cells were cultured in a volume of 180 μL of Dulbecco's modified Eagle's medium (DMEM) in a 96-well plate at a density of 250,000 to 450,000 cells/mL for 24 hours. The Dulbecco's modified Eagle's medium (DMEM) contained 4.5 g/L glucose, 50 U/mL penicillin, 50 mg/mL streptomycin, 100 mg/mL Normocin, 2 mM L-glutamine, and 10% (v/v) heat-inactivated fetal bovine serum. HEK293-Blue-hTLR-7 cells were then incubated with 20 μL of serially diluted test compounds at a final concentration of 1% DMSO and incubated at 37° C. in a CO ₂ incubator for 20 hours. Then 20 μL of supernatant from each well was incubated with 180 μL of Quanti-blue substrate solution at 37°C for 1-3 hours, and the absorbance was read spectrophotometrically at 620-655 nm. It is widely accepted that TLR7 activation leads to downstream NF-κB activation in the signal transduction pathway, and similar reporter gene assays have been widely used to evaluate TLR7 agonists (Tsuneyasu Kaisho and Takashi Tanaka, Trends in Immunology, Vol. 29, No. 7, July 2008, p. 2329; Hiroaki Hemmi et al., Nature Immunology 3, 196-200 (2002).

Compounds of the invention as described herein were tested for TLR7 agonist activity in the above assays and the results are listed in Table 1. Compounds of the Examples were found to have _EC50s of about 3 μM to about 470 μM. Specific compounds of Formula (I) or (Ia) were found to have _EC50s of about 3 μM to about 42 μM.

Table 1: Activity of compounds in HEK293-hTLR-7 assay

Example No. Example 1-P1 317 Example 2-P1 144 Example 3-P1 469 Example 4-P1 13 Example 5-P1 twenty four Example 6-P1 twenty three Example 7-P1 28 Example 8-P1 2.5 Example 9-P3 twenty two Example 10-P3 twenty three Example 11-P3 321 Example 12-P3 42 Example 13-P3 15 Example 14-P3 10

Example 18

Metabolism of prodrugs: Compounds of formula (II)

Studies are conducted to evaluate the metabolic conversion of prodrug compounds of formula (II) or (IIa) to compounds of formula (I) or (Ia) of the present invention. If administered as a prodrug, the prodrug compound of formula (II) or (IIa) can be metabolized in vivo to the active compound of formula (I) or (Ia) and other compounds of the present invention. Hepatocytes are typically used to evaluate the extent of metabolic conversion of prodrugs in animals or humans.

A study was conducted to evaluate the metabolic conversion of the prodrug Example 15 to the corresponding active form Example 5-P1 in the presence of human hepatocytes. The formation of the active form Example 5-P1 was monitored in this study. For comparison, the metabolic conversion of famciclovir to penciclovir was also evaluated.

Hepatocyte suspension

Cryopreserved hepatocyte plating medium (catalog number: PY-HMD-03) was purchased from RILD Research Institute for Liver Diseases (Shanghai) Co. Ltd., and cryopreserved human hepatocytes (catalog number: X008005, batch number: VRR) were purchased from Bioreclamation IVT (Baltimore, MD).

A hepatocyte stock suspension was prepared from cryopreserved hepatocytes at a concentration of 1.8 x ¹⁰⁶ cells/mL in plating medium.

Working solution of compound

Compounds were dissolved in DMSO to make 10 mM stock solutions. 10 μL of the stock solution was diluted into 990 μL of plating medium to make 100 μM working solutions.

Incubation

In a 24-well cell culture plate, prepare the reaction suspension by mixing 200 μL of human hepatocyte suspension with 200 μL of working solution. The final incubation contains 0.9× ¹⁰ cells/mL and 50 μM compound. Incubate the mixture at 37°C in a humidified 5% _CO atmosphere with shaking at 900 rpm.

Preparation of analytical samples

After 180 min of incubation, 200 μL of the incubation mixture was transferred to a 1.5 mL tube and quenched with 400 μL of stop solution (ice-cold acetonitrile containing 0.2 μM tolbutamide as an internal standard). The sample was centrifuged at 14,000 rpm for 10 minutes, and the resulting supernatant was subjected to LC-MS/MS analysis.

Prepare a calibration curve as follows. To 200 μL of cell suspension (cell density 1.8 million cells/mL), add 198 μL of hepatocyte culture medium and 2 μL of the appropriate compound concentration in DMSO. Mix the sample thoroughly, and transfer 200 μL of this mixture to 400 μL of stop solution (see above). The standard curve range is 1 μM to 25 μM.

Biological analysis

The compounds were quantified using an API 5500 LC-MC/MC instrument in ESI-positive MRM mode. The results of prodrug conversion and metabolite generation are summarized in Table 2.

Table 2: Concentrations of metabolites formed in human hepatocytes after 3 h incubation with 50 μM prodrug

Example No. metabolites Concentration of product in human hepatocytes (μM) Example 15 Example 5-P1 0.63 Famciclovir Penciclovir 18

In human hepatocytes, the compound of Example 15 and famciclovir were metabolized to the corresponding active metabolites Example 5-P1 and penciclovir, respectively.

Claims (28)

1. A compound of formula (I) or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, in ^R1 is OH; ^R2 is H; ^R3 is H, _C1-6 alkyl, _C2-6 alkenyl, or _C3-7 cycloalkyl; W is -CH _2- or -C(C _1-6 alkyl) _2- ; A is OH, _C1-6 alkoxy, _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or a heterocyclic amino group selected from pyrrolidinyl, piperidinyl, or morpholinyl. 2. The compound of claim 1 or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R1 is OH; ^R2 is H; R ³ is H, methyl, ethyl, butyl, allyl, or cyclopropyl; W is _-CH2- or -C( _CH3 ) _2- ; A can be OH, methoxy, _CH3NH- , ( _CH3 ) _2N- , or morpholino. 3. The compound of claim 1 or a pharmaceutically acceptable salt thereof, enantiomer or diastereomer, wherein the compound is a compound of formula (Ia): in ^R1 is OH; ^R2 is H; ^R3 is H, _C1-6 alkyl, _C2-6 alkenyl, or _C3-7 cycloalkyl; W is -CH _2- or -C(C _1-6 alkyl) _2- ; A is OH, _C1-6 alkoxy, _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or a heterocyclic amino group selected from pyrrolidinyl, piperidinyl, or morpholinyl. 4. The compound of claim 3 or a pharmaceutically acceptable salt thereof, enantiomer or diastereomer, wherein... ^R1 is OH; ^R2 is H; R ³ is H, methyl, ethyl, butyl, allyl, or cyclopropyl; W is _-CH2- or -C( _CH3 ) _2- ; A can be OH, methoxy, _CH3NH- , ( _CH3 ) _2N- , or morpholino. 5. The compound of any one of claims 1 or 3, or a pharmaceutically acceptable salt thereof, enantiomer or diastereomer, wherein ^R3 is a _C1-6 alkyl, _C2-6 alkenyl or _C3-7 cycloalkyl. 6. The compound of any one of claims 1 or 3, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein ^R3 is methyl, ethyl, cyclopropyl, or allyl. 7. The compound of any one of claims 1 or 3, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein W is _-CH2- . 8. The compound according to any one of claims 1 or 3, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R1 is OH; ^R2 is H; ^R3 is a _C1-6 alkyl or _C3-7 cycloalkyl; W is -CH ₂ -; A is OH, _C1-6 alkoxy, _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or morpholino. 9. The compound according to any one of claims 1 or 3, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R1 is OH; ^R2 is H; ^R3 is methyl, ethyl, or cyclopropyl; W is -CH ₂ -; A can be OH, methoxy, _CH3NH- , ( _CH3 ) _2N- , or morpholino. 10. The compound according to claim 1, selected from: 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]-N,N-dimethylacetamide; 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]-N,N-dimethylacetamide; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentane-4-yl]acetic acid; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N-methylacetamide; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N-methylacetamide; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N,N-dimethylacetamide; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N,N-dimethylacetamide; 5-Amino-3-[(4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxothiacyclopentan-5-yl]-6H-thiazo[4,5-d]pyrimidine-2,7-dione; 5-Amino-3-[(2S,4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxothiacyclopentan-5-yl]-6H-thiazo[4,5-d]pyrimidine-2,7-dione; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypentyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxybut-3-enyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[5-(5-amino-7-hydroxy-2-oxo-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]-2-methyl-propionic acid; Or its medicinal salt, enantiomer or diastereomer. 11. The compound according to claim 1, selected from: 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[(trans-2,4-trans-4,5)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-(hydroxymethyl)-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]methyl acetate; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentane-4-yl]acetic acid; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N-methylacetamide; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N-methylacetamide; 2-[(4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N,N-dimethylacetamide; 2-[(2S,4S,5R)-5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxypropyl]-1,3-oxothiacyclopentan-4-yl]-N,N-dimethylacetamide; 5-Amino-3-[(4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxothiacyclopentan-5-yl]-6H-thiazo[4,5-d]pyrimidine-2,7-dione; 5-Amino-3-[(2S,4S,5R)-2-[(1S)-1-hydroxypropyl]-4-(2-morpholino-2-oxo-ethyl)-1,3-oxothiacyclopentan-5-yl]-6H-thiazo[4,5-d]pyrimidine-2,7-dione; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(1S)-1-hydroxyethyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; 2-[5-(5-amino-2,7-dioxo-6H-thiazo[4,5-d]pyrimidin-3-yl)-2-[(S)-cyclopropyl(hydroxy)methyl]-1,3-oxothiacyclopentan-4-yl]acetic acid; Or its medicinal salt, enantiomer or diastereomer. 12. A compound of formula (II) or a pharmaceutically acceptable salt thereof, enantiomer or diastereomer, in ^R4 is H, _C1-6 alkylcarbonyl, phenylcarbonyl, or _C1-6 alkylphenylcarbonyl; R ⁵ is H, _C1-6 alkyl, _C2-6 alkenyl, or _C3-7 cycloalkyl; W is -CH _2- or -C(C _1-6 alkyl) _2- ; A is OH, _C1-6 alkoxy, _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or a heterocyclic amino group selected from pyrrolidinyl, piperidinyl, or morpholinyl. 13. The compound of claim 12 or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R4 is H, acetyl, phenylcarbonyl, or methylphenylcarbonyl; R ⁵ is H, methyl, ethyl, butyl, allyl, or cyclopropyl; W is _-CH2- or -C( _CH3 ) _2- ; A can be OH, methoxy, _CH3NH- , ( _CH3 ) _2N- , or morpholino. 14. The compound of claim 12 or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein the compound is a compound of formula (IIa): in ^R4 is H, _C1-6 alkylcarbonyl, phenylcarbonyl, or _C1-6 alkylphenylcarbonyl; R ⁵ is H, _C1-6 alkyl, _C2-6 alkenyl, or _C3-7 cycloalkyl; W is -CH _2- or -C(C _1-6 alkyl) _2- ; A is OH, _C1-6 alkoxy, _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or a heterocyclic amino group selected from pyrrolidinyl, piperidinyl, or morpholinyl. 15. The compound of claim 14 or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R4 is H, acetyl, phenylcarbonyl, or methylphenylcarbonyl; ^R5 is H, methyl, ethyl, butyl, allyl, or cyclopropyl; W is _-CH2- or -C( _CH3 ) _2- ; A can be OH, methoxy, _CH3NH- , ( _CH3 ) _2N- , or morpholino. 16. The compound of any one of claims 12 to 15, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein ^R4 is a phenyl carbonyl group. 17. The compound of any one of claims 12 or 14, or a pharmaceutically acceptable salt thereof, enantiomer or diastereomer, wherein ^R5 is a _C1-6 alkyl, _C2-6 alkenyl or _C3-7 cycloalkyl. 18. The compound of any one of claims 12 or 14, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein ^R5 is methyl, ethyl, cyclopropyl, or allyl. 19. The compound of any one of claims 12 or 14, or a pharmaceutically acceptable salt thereof, enantiomer or diastereomer, wherein W is _-CH2- . 20. The compound of any one of claims 12 or 14, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R4 is a phenyl carbonyl group; R ⁵ is a _C1-6 alkyl or _C3-7 cycloalkyl; W is -CH ₂ -; A is OH, _C1-6 alkoxy, _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or morpholino. 21. The compound according to any one of claims 12 or 14, or a pharmaceutically acceptable salt, enantiomer, or diastereomer thereof, wherein... ^R4 is a phenyl carbonyl group; ^R5 is methyl, ethyl, or cyclopropyl; W is -CH ₂ -; A can be OH, methoxy, _CH3NH- , ( _CH3 ) _2N- , or morpholino. 22. The compound according to any one of claims 12 or 14, wherein the compound is benzoic acid [(1S)-1-[(2S,4S,5R)-5-(5-amino-2-oxo-thiazo[4,5-d]pyrimidin-3-yl)-4-(2-methoxy-2-oxo-ethyl)-1,3-oxothiacyclopentan-2-yl]propyl] ester; or a pharmaceutically acceptable salt, enantiomer or diastereomer thereof. 23. A method for preparing a compound according to any one of claims 1, 3, 12 or 14, comprising the following steps: (a) Reacting the compound of formula (XI) with a base, Where ^Ra is H or ^R1 ; or (b) Reacting the compound of formula (XII) with a base, Where ^Ra is H or ^R1 ; or (c) Reacting the compound of formula ( ^XIII ) with ^R6R7NH in the presence of a coupling agent, Where ^Ra is H or ^R1 ; ^R6R7N- is a _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- ^, or a heterocyclic amino group selected from pyrrolidinyl, piperidinyl, or morpholinyl; or (d) React the compound of formula (P7) with a base. Where ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ; or (e) Reacting the compound of formula (XXVI) with a base, Where ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ; or (f) Reacting the compound of formula (XXVII) with a base, Where ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ; or (g) Reacting the compound of formula ( ^XXVIII ) with ^R6R7NH in the presence of a coupling agent, Where ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ; ^{R6 and R7} N- are _C1-6 alkyl NH-, ( _C1-6 alkyl) _2N- , or heterocyclic amino groups selected from pyrrolidinyl, piperidinyl, or morpholinyl; or (h) The compound of formula (XXV) is reacted with compound (X), The reaction occurs in the presence of a silyl etherifying agent and a Lewis acid. Where ^Ra is H or ^R1 ; ^Rb is ^R3 or ^R5 ; Wherein ^R1 , ^R2 and ^R3 are as defined in claim 1 or 3, and ^R5 is as defined in claim 12 or 14. 24. A compound, or pharmaceutically acceptable salt, enantiomer, or diastereomer, according to any one of claims 1-22, used as a therapeutically active substance. 25. A pharmaceutical composition comprising a compound according to any one of claims 1-22 and a therapeutic inert carrier. 26. Use of the compound according to any one of claims 1-22 in the preparation of a medicament for treating or preventing hepatitis B virus infection. 27. A compound or pharmaceutically acceptable salt, enantiomer or diastereomer of any one of claims 1-22 for the treatment or prevention of hepatitis B virus infection. 28. A compound or pharmaceutically acceptable salt, enantiomer or diastereomer prepared by the method of claim 23 according to any one of claims 1-22.