CN115991678A - A kind of diketopiperazine compound, preparation method and application thereof - Google Patents

Abstract

The invention discloses a diketopiperazine compound, a preparation method and an application thereof. The present invention provides a diketopiperazine compound represented by formula I or a pharmaceutically acceptable salt thereof, which can be used as self-assembled drug-loaded microspheres to realize effective delivery of drugs.

Description

A diketopiperazine compound, preparation method and application thereof

Technical Field

The invention relates to a diketopiperazine compound, a preparation method and application thereof.

Background Art

Drug delivery systems have always been an important direction in drug preparation research. Traditional methods are affected by the pH environment of the digestive tract and various enzymes, which causes some bioactive substances such as calcitonin, insulin, and mucopolysaccharides to be affected in the gastrointestinal tract and quickly destroyed or inactivated. At the same time, due to the physical and chemical properties of the drugs themselves, some sensitive drugs are prone to degradation, and poorly soluble drugs have low bioavailability. Developing an efficient delivery system can enhance drug efficacy and reduce toxic side effects.

Diketopiperazine derivatives are a new type of material that can precipitate and self-assemble into microspheres in acidic solutions. The microspheres have a large surface area, high drug loading capacity, and a simple manufacturing process. They are suitable for the preparation of various types of drugs, such as cationic drugs with API molecular weights of 500-140000Da, anionic drugs, hydrophilic/lipid drugs, peptides, proteins, and small molecule drugs.

Due to their small diameter, the microsphere dry powder prepared by this technology can be used for pulmonary inhalation administration, and their in vivo absorption rate can reach the absorption rate of simulated arterial injection; or they can be used directly for injection. Both routes can avoid the first-pass effect of the liver and peripheral circulation degradation.

技术，是一种新颖的药物递送技术。Mannkind公司利用该技术生产的商品名为Afrezza的速效胰岛素，2014年被FDA批准上市，成为目前市场上唯一的胰岛素吸入制剂。Preparation of microspheres using fumaryl diketopiperazine (FDKP, CAS: 176738-91-3) as carrier

Technology is a novel drug delivery technology. Mannkind used this technology to produce a rapid-acting insulin called Afrezza, which was approved by the FDA in 2014 and is currently the only insulin inhalation preparation on the market.

技术的关键载体材料FDKP专利(WO2013/162764、CN104797563)提及了该材料的合成方法。其母核的合成方法Katchalski在1946年提出以氨基酸酯衍生物二聚体如二肽酯脱水环合而成，Kopple在1968年提出的二酮哌嗪类有机化合物的合成方法是由氨基酸衍生物在高沸腾有机溶剂中热脱水而成。于清在CN201010206311.5中报道了3,6-双(4-双反丁烯二酰基氨丁基)-2,5-二酮哌嗪及其盐取代物的合成方法。

The key carrier material FDKP patent of the technology (WO2013/162764, CN104797563) mentioned the synthesis method of the material. The synthesis method of its mother core was proposed by Katchalski in 1946, which was to dehydrate and cyclize the dimer of amino acid ester derivatives such as dipeptide esters. The synthesis method of diketopiperazine organic compounds proposed by Kopple in 1968 was to thermally dehydrate amino acid derivatives in a high boiling organic solvent. Yu Qing reported the synthesis method of 3,6-bis (4-bis-trans-butylene diaminobutyl) -2,5-diketopiperazine and its salt substitutes in CN201010206311.5.

Since diketopiperazine derivatives can self-assemble into drug-loaded microspheres by adjusting the pH value of the preparation system, they have certain advantages as carriers. Therefore, replacing FDKP with new diketopiperazine derivatives and developing a series of successful and effective substances and their salt substitutes have practical significance for achieving effective drug delivery.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the single defect of diketopiperazine derivatives in the prior art, and to provide a diketopiperazine compound with novel structure, a preparation method and its application. The diketopiperazine compound provided by the present invention can be used as a self-assembled drug-loaded microsphere to achieve effective drug delivery.

The present invention provides a diketopiperazine compound or a pharmaceutically acceptable salt thereof as shown in Formula I,

-N(R²)R³-、-5-10元杂芳基-、-3-12元环脂烃基-和-3-7元杂环烷基-；所述的-5-10元杂芳基-中的杂原子选自N、O和S中的一种或多种，杂原子数为1-4个；所述的-3-7元杂环烷基-中的杂原子选自N、O、S、S(＝O)和S(＝O)₂中的一种或多种，杂原子数为1-3个；当取代基为多个时，相同或不同；Wherein, ^Ra and ^Ra ' are independently selected from the following groups which are unsubstituted or substituted by one or more ^R4 : _-C1 - _C6 alkylene-,

-N(R ² )R ³ -, -5-10 membered heteroaryl-, -3-12 membered cycloaliphatic- and -3-7 membered heterocycloalkyl-; the heteroatoms in the -5-10 membered heteroaryl- are selected from one or more of N, O and S, and the number of heteroatoms is 1-4; the heteroatoms in the -3-7 membered heterocycloalkyl- are selected from one or more of N, O, S, S(=O) and S(=O) ₂ , and the number of heteroatoms is 1-3; when there are multiple substituents, they may be the same or different;

R ⁴ is selected from C ₁ -C ₆ alkyl, C ₁ -C ₆ alkyl-O-, C ₁ -C ₆ alkyl substituted by one or more halogens, and -NHC(=O)-R ⁵ ;

^R1 and ^R3 are independently _-C1 - _C6 alkylene-;

R ² and R ⁵ are independently selected from H or C ₁ -C ₆ alkyl;

The carbon atom with "*" indicates that when it is a chiral carbon atom, it is in S configuration, R configuration or a mixture thereof.

In the present invention, when ^Ra and ^Ra ' are independently unsubstituted or substituted by one or more ^R4 with _-C1 - _C6 alkylene-, the _-C1 - _C6 alkylene- is independently _-C1 - _C4 alkylene-, and the _-C1 - _C4 alkylene- is preferably -methylene-, _-CH2CH2- , -( _CH ( _{CH3 ) )} - _, -CH2CH2CH2- _{, -(C(CH3)2 )} - _{, -CH2CH2CH2CH2- , -} (CH( _CH3 )) _{CH2CH2- or -CH2CH} ( _CH3 ) _CH2- , for example _{, -methylene- , -CH2CH2-} or _-CH2CH2CH2- .

In the present invention, when ^Ra and ^Ra ' are independently -5-10 membered heteroaryl- which is unsubstituted or substituted by one or more ^R4 , the -5-10 membered heteroaryl- is -5-6 membered heteroaryl-, wherein the heteroatom is selected from one or more of N, O and S, the number of heteroatoms is 1-2, preferably -pyridyl-, -thienyl-, for example

所述的-4-7元环烯基-优选为-环丙烯基-、-环丁烯基-、-戊烯基-、-环己烯基-、-环庚烯基-，例如

In the present invention, when ^Ra and ^Ra ' are independently unsubstituted or substituted by one or more ^R4 -3-12-membered cycloaliphatic group-, the -3-12-membered cycloaliphatic group- is preferably -3-7-membered cycloalkyl- or -4-7-membered cycloalkenyl-. The -3-7-membered cycloalkyl- is preferably -cyclopropyl-, -cyclobutyl-, -cyclopentyl-, -cyclohexyl- or -bicyclo[1.1.1]pentyl-, for example

The -4-7 membered cycloalkenyl- is preferably -cyclopropenyl-, -cyclobutenyl-, -pentenyl-, -cyclohexenyl-, -cycloheptenyl-, for example

In the present invention, when ^R1 and ^R3 are independently _-C1 - _C6 alkylene-, the _-C1 - _C6 alkylene- is independently _-C1 - _C4 alkylene-, and _{the -C1} - _C4 alkylene- is preferably -methylene-, _-CH2CH2- , -(CH _{( CH3} ))-, _-CH2CH2CH2- , -(C(CH3 _{)2 ) -} , _{-CH2CH2CH2CH2-} , -( _CH ( _CH3 )) _{CH2CH2- or -CH2CH (CH3 ) CH2- ,} for example, _-methylene- or _-CH2CH2- .

In the present invention, when ^R2 and ^R5 are independently _C1 - _C6 alkyl, the C1 _{- C6} alkyl is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, such as methyl.

In the present invention, when ^R4 is C1 _{- C6} alkyl, _C1 - _C6 alkyl-O-, or C1-C6 alkyl substituted by one or more halogens, the C1- _C6 alkyl in the _{C1 - C6} alkyl, _{C1 - C6} alkyl-O-, or _C1 - _C6 alkyl substituted by one or more halogens is independently _C1 - _C4 alkyl, and the _C1 - _C4 alkyl is preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, for example _, methyl.

In the present invention, when R ⁴ is a C ₁ -C ₆ alkyl group substituted by one or more halogens, the number of the halogens may be 1 to 3. The halogens may be fluorine, chlorine, bromine or iodine, for example, fluorine or chlorine.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

-N(R²)R³-、-5-10元杂芳基-和-3-12元环脂烃基-。 ^Ra and Ra ^' are independently selected from _-C1 - _C6 alkylene- substituted by one or more _C1 - _C6 alkyl, _-C1 - _C6 alkylene- substituted by one or more -NHC(=O) ^-R5 ,

-N(R ² )R ³ -, -5- to 10-membered heteroaryl- and -3- to 12-membered cycloaliphatic-.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

The connection mode of the -N(R ² )R ³ - is preferably that the N atom is connected to the amide bond in Formula I, and R ³ is connected to the carboxyl group in Formula I.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

的连接方式优选为烯基与所述的如式I中的酰胺键连接，R¹与所述的如式I中的羧基连接。Said

The connection mode of is preferably that the alkenyl group is connected to the amide bond in Formula I, and R ¹ is connected to the carboxyl group in Formula I.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

^R2 is selected from H.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

R ⁴ is selected from C ₁ -C ₆ alkyl or -NHC(=O)-R ⁵ .

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

R ⁵ is selected from C ₁ -C ₆ alkyl.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

^Ra and ^Ra ' are the same or different, for example, the same.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

的构型主要为

(即

)、

(即

)、

(即

)、

(即

)所示的构型或它们的混合物；In the diketopiperazine compound as shown in Formula I,

The configuration is mainly

(Right now

),

(Right now

),

(Right now

),

(Right now

) or a mixture thereof;

For example, for each chiral center, greater than 80% ee; for another example, for each chiral center, the configuration is about 85%-90% excess over the other configuration, more preferably about 95%-99% excess, more preferably about 99% excess, or no other configuration can be detected.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

-N(R²)R³-、-5-10元杂芳基-和-3-12元环脂烃基-； ^Ra and Ra ^' are independently selected from _-C1 - _C6 alkylene- substituted by one or more _C1 - _C6 alkyl, _-C1 - _C6 alkylene- substituted by one or more -NHC(=O) ^-R5 ,

-N(R ² )R ³ -, -5- to 10-membered heteroaryl-, and -3- to 12-membered cycloaliphatic-;

^R1 and ^R3 are independently _-C1 - _C6 alkylene-;

^R2 is H;

R ⁵ is C ₁ -C ₆ alkyl;

^Ra and ^Ra ' are the same.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

-N(R²)R³-、-5-10元杂芳基-和-3-12元环脂烃基-； ^Ra and ^Ra ' _are independently selected from _{-C1 - C6} alkylene-, ...

-N(R ² )R ³ -, -5- to 10-membered heteroaryl-, and -3- to 12-membered cycloaliphatic-;

^R1 and ^R3 are independently _-C1 - _C6 alkylene-;

^R2 is H;

R ⁵ is C ₁ -C ₆ alkyl;

^Ra and ^Ra ' are the same.

In certain preferred embodiments of the present invention, certain groups in the diketopiperazine compound as shown in Formula I are defined as follows (the groups not mentioned are the same as those described in any embodiment of the present application),

其中b位置的连接键与所述的如式I中的酰胺连接，c位置的连接键与所述的如式I中的羧基连接。 ^Ra and Ra ^' are independently

The connecting bond at position b is connected to the amide in Formula I, and the connecting bond at position c is connected to the carboxyl group in Formula I.

In one embodiment of the present invention, the diketopiperazine compound as shown in Formula I is selected from any of the following structures, isomers thereof or mixtures thereof:

In the present invention, the diketopiperazine compound or its pharmaceutically acceptable salt as shown in Formula I has one or more chiral carbon atoms, so it can be separated to obtain optically pure isomers, such as pure enantiomers, or racemates, or mixed isomers. Pure single isomers can be obtained by separation methods in the art, such as chiral crystallization into salts, or separation by chiral preparative columns.

In the present invention, the diketopiperazine compound or its pharmaceutically acceptable salt as shown in Formula I may exist in a crystalline or amorphous form. The term "crystalline form" means that the ions or molecules therein are arranged in a strict periodic manner in three-dimensional space in a certain manner, and have a regularity of periodic repetition at a certain distance; due to the different periodic arrangements, there may be multiple crystal forms, that is, polymorphism. The term "amorphous form" means that the ions or molecules therein are in a disorderly distribution state, that is, there is no periodic arrangement between the ions and molecules.

In the present invention, the diketopiperazine compound or its pharmaceutically acceptable salt as shown in Formula I, if stereoisomers exist, can exist in the form of a single stereoisomer or a mixture thereof (e.g., a racemate). The term "stereoisomer" refers to cis-trans isomers or optical isomers. These stereoisomers can be separated, purified and enriched by asymmetric synthesis methods or chiral separation methods (including but not limited to thin layer chromatography, rotary chromatography, column chromatography, gas chromatography, high pressure liquid chromatography, etc.), and can also be obtained by chiral separation by bonding (chemical bonding, etc.) or salt formation (physical bonding, etc.) with other chiral compounds. The term "single stereoisomer" means that the mass content of one stereoisomer of the compound of the present invention relative to all stereoisomers of the compound is not less than 95%.

In the present invention, if the diketopiperazine compound as shown in Formula I or its pharmaceutically acceptable salt exists in tautomers, it may exist in the form of a single tautomer or a mixture thereof, preferably in the form of a relatively stable tautomer as the main tautomer.

The present invention also includes isotopically labeled diketopiperazine compounds or pharmaceutically acceptable salts thereof as shown in Formula I of the present invention, wherein one or more atoms are replaced by one or more atoms having a specific atomic mass or mass number. Examples of isotopes that can be incorporated into the compounds of the present invention include, but are not limited to, isotopes of hydrogen, carbon, nitrogen, oxygen, fluorine, sulfur and chlorine (e.g., ² H, ³ H, ¹³ C, ¹⁴ C, ¹⁵ N, ¹⁸ O, ¹⁷ O, ¹⁸ F, ³⁵ S and ³⁶ Cl). Isotopically labeled compounds of the present invention can be used for determination of tissue distribution of compounds, prodrugs and metabolites thereof; preferred isotopes for such determinations include ³ H and ¹⁴ C. In addition, in some cases, substitution with heavier isotopes (e.g., deuterium (2H or D)) can provide increased metabolic stability, which provides therapeutic advantages, such as increased in vivo half-life or reduced dosage requirements.

Isotopically labeled compounds of the present invention can generally be prepared according to the methods described herein by substituting an isotopically labeled reagent for a non-isotopically labeled reagent.

In the present invention, the diketopiperazine compound or its pharmaceutically acceptable salt as shown in formula I can be synthesized by methods similar to those known in the chemical field, and the steps and conditions thereof can refer to the steps and conditions of similar reactions in the art, especially according to the description herein. The starting materials are usually from commercial sources, such as Aldrich, or can be easily prepared using methods known to those skilled in the art (obtained through SciFinder, Reaxys online database).

In the present invention, the diketopiperazine compound as shown in Formula I or a pharmaceutically acceptable salt thereof can also be prepared by peripherally modifying the prepared diketopiperazine compound as shown in Formula I or a pharmaceutically acceptable salt thereof using conventional methods in the art to obtain other diketopiperazine compounds as shown in Formula I or a pharmaceutically acceptable salt thereof.

The necessary raw materials or reagents for preparing the diketopiperazine compounds or pharmaceutically acceptable salts thereof as shown in Formula I can be commercially available or prepared by synthetic methods known in the art. The method described in the following experimental section can prepare the compounds of the present invention in the form of free bases or salts thereof by addition of acids. The term pharmaceutically acceptable salt refers to a pharmaceutically acceptable salt as defined herein and has all the effects of the parent compound. Pharmaceutically acceptable salts can be prepared by adding the corresponding acid to a suitable organic solvent for an organic base and treating according to conventional methods to prepare pharmaceutically acceptable salts.

Examples of salt formation include: For base addition salts, it is possible to prepare alkali metal (such as sodium, potassium or lithium) or alkaline earth metal (such as aluminum, magnesium, calcium, zinc or bismuth) salts by treating a compound of the invention having an appropriate acidic proton with an alkali metal or alkaline earth metal hydroxide or alkoxide (such as ethanolate or methanolate) or a suitable basic organic amine (such as diethanolamine, choline or meglumine) in an aqueous medium.

Alternatively, for acid addition salts, salts with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid; and salts formed with organic acids such as acetic acid, benzenesulfonic acid, benzoic acid, camphorsulfonic acid, citric acid, ethanesulfonic acid, fumaric acid, glucoheptonic acid, glutamic acid, glycolic acid, hydroxynaphthoic acid, 2-hydroxyethanesulfonic acid, lactic acid, maleic acid, malic acid, oxalic acid, pyruvic acid, malonic acid, mandelic acid, methanesulfonic acid, 2-naphthalenesulfonic acid, propionic acid, salicylic acid, succinic acid, tartaric acid, citric acid, cinnamic acid, p-toluenesulfonic acid or trimethylacetic acid.

The "compounds of the present invention" or "compounds shown in the present invention" include any diketopiperazine compound shown in Formula I or a pharmaceutically acceptable salt thereof. The compounds of the present invention may also exist in the form of hydrates or solvates.

The present invention also provides a pharmaceutical composition, which comprises the diketopiperazine compound shown in Formula I as described above or a pharmaceutically acceptable salt thereof, and one or more active pharmaceutical ingredients; it may also comprise one or more other pharmaceutical excipients; the active pharmaceutical ingredients may be in a therapeutically and/or preventively effective amount.

The pharmaceutical composition can be a microsphere drug delivery system. The diketopiperazine compound or a pharmaceutically acceptable salt thereof as shown in formula I is a self-assembled microsphere.

The weight percentage of the active pharmaceutical ingredient in the pharmaceutical composition is 10% to 90%, for example 20% to 80%.

The active pharmaceutical ingredient (drug) can be a cationic drug, anionic drug, hydrophilic/lipid drug, polypeptide, protein, or small molecule drug with an API molecular weight of 500-140,000 Da; for example, selected from insulin, dolutegravir, sildenafil, etc.

For example, the active pharmaceutical ingredient (drug) is a poorly soluble drug.

The preparation method of the pharmaceutical composition as described above can be conventional in the art.

The present invention also provides a method for preparing the pharmaceutical composition as described above, comprising the following steps:

After adding the solution containing the active pharmaceutical ingredient (drug) to the alkaline solution containing the diketopiperazine compound or its pharmaceutically acceptable salt as shown in Formula I, adjusting the pH to precipitate solids, the pharmaceutical composition can be obtained. The mass ratio of the active pharmaceutical ingredient (drug) to the diketopiperazine compound or its pharmaceutically acceptable salt as shown in Formula I can be 7:10; the alkaline solution can be obtained by adding 1% ammonia water (v/v); the pH can be 5.0; the adjusted pH can be obtained by adding 10% glacial acetic acid aqueous solution (v/v); the obtained pharmaceutical composition is preferably filtered, washed and then dried.

The present invention also provides a use of the diketopiperazine compound or a pharmaceutically acceptable salt thereof as described above as Formula I as a preparation excipient; for example, it forms drug-loaded microspheres. Specifically, the diketopiperazine compound or a pharmaceutically acceptable salt thereof as described above as Formula I can be made into drug carrier particles with suitable properties (such as particle size, shape, structural strength, solubility, and low toxicity, etc.), and the drug microparticles formed by loading the effective drug ingredients onto such drug carrier particles can be stable at low pH values, decompose at physiological pH values, and are suitable for oral administration, injection, or inhalation, etc. to achieve effective drug delivery. ).

The present invention also provides a method for preparing the diketopiperazine compound as shown in formula I as described above, comprising the following steps: subjecting the compound as shown in formula II to a saponification reaction as shown below in a solvent in the presence of a base to obtain the diketopiperazine compound as shown in formula I;

wherein, *, ^Ra and Ra ^' are defined as above; R' and R" are independently _C1 - _C8 alkyl (e.g., _C1 - _C6 alkyl, and also C1- _C4 alkyl, wherein the _{C1 - C4} alkyl is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl; and also methyl, tert-butyl).

In the preparation method of the diketopiperazine compound as shown in Formula I, the conditions and operation of the saponification reaction shown can be conventional conditions and operations in this type of reaction in the art; in the present invention, the following are preferred:

The solvent may be an alcohol solvent (such as methanol and/or ethanol). The amount of the solvent used does not affect the reaction, for example, the volume mass ratio of the solvent to the compound shown in Formula II is 1 mL/g-50 mL/g, for example 5 mL/g.

The base may be an alkali metal hydroxide (eg, sodium hydroxide and/or potassium hydroxide).

The volume mass ratio of the solvent to the base is 5 mL/g-20 mL/g (eg 10 mL/g).

The molar ratio of the base to the compound of Formula II may be 2:1-10:1 (eg, 4:1).

The temperature of the saponification reaction shown may be from room temperature to 80°C (eg, 60-70°C).

The progress of the saponification reaction can be monitored by conventional monitoring methods in the art (such as TLC, HPLC or NMR), and the reaction endpoint is generally taken as the disappearance or no-reaction of the compound shown in Formula II.

The preparation method may further include post-treatment and crystallization; the post-treatment may include the following steps: after the saponification reaction is completed, acid is added for neutralization (such as glacial acetic acid), solids are precipitated, and the diketopiperazine compound as shown in formula I is obtained.

The crystallization may include the following steps: filtering the mixture of the diketopiperazine compound shown in Formula I and trifluoroacetic acid obtained after the above-mentioned post-treatment, mixing the filtrate with glacial acetic acid, cooling to precipitate solid, filtering, washing, and obtaining the crystal of the diketopiperazine compound shown in Formula I. The mixture of the diketopiperazine compound shown in Formula I and trifluoroacetic acid may be obtained by mixing the diketopiperazine compound shown in Formula I with trifluoroacetic acid at 50°C-100°C (e.g., 80°C-90°C). The solvent used for the washing may be an alcohol solvent (e.g., ethanol and/or ethanol).

The preparation method may further include the following steps: in a solvent, in the presence of a base and a condensing agent, subjecting the compound represented by formula III to a condensation reaction as shown below to obtain the compound represented by formula II;

wherein *, ^Ra , ^Ra ', R' and R" are as defined above; and ^Ra and ^Ra ' are the same, and R' and R" are the same.

The conditions and operations of the condensation reaction shown may be conventional conditions and operations in this type of reaction in the art; in the present invention, the following are preferred:

Wherein, the solvent can be one or more of amide solvents (e.g., N,N-dimethylformamide DMF and/or N,N-dimethylacetamide DMA), sulfoxide solvents (e.g., dimethyl sulfoxide DMSO), halogenated hydrocarbon solvents (e.g., dichloromethane DCM) and cyclic ether solvents (e.g., tetrahydrofuran THF); for example, amide solvents (e.g., N,N-dimethylformamide DMF and/or N,N-dimethylacetamide DMA), sulfoxide solvents (e.g., dimethyl sulfoxide DMSO), halogenated hydrocarbon solvents (e.g., dichloromethane DCM) and cyclic ether solvents (e.g., tetrahydrofuran THF). The amount of the solvent used is such that it does not affect the reaction.

In the condensation reaction, the base may be an organic base (eg, triethylamine). The molar ratio of the base to the compound of formula III is 1.5:1-3:1 (eg, 2:1-2.5:1).

In the condensation reaction, the condensing agent may be one or more of HATU (2-(7-azabenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate), EDTA (ethylenediaminetetraacetic acid) and HBTU (benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate), preferably HATU and/or EDTA. The molar ratio of the condensing agent to the compound shown in Formula III is 1.0:1-2:1 (e.g., 1:1-1.5:1).

In the condensation reaction, the molar ratio of the compound shown in Formula IV to the compound shown in Formula III is 2:1-1:1.

The condensation reaction temperature may be from room temperature to 80° C. (eg, 10-30° C.).

The progress of the condensation reaction can be monitored by conventional monitoring methods in the art (such as TLC, HPLC or NMR), and the reaction endpoint is generally taken as the disappearance or no-reaction of the compound shown in Formula III.

The preparation method may further include post-treatment and crystallization; the post-treatment and crystallization may include the following steps: after the condensation reaction is completed, the filter cake obtained by filtration is crystallized in glacial acetic acid and water to precipitate a solid to obtain the compound shown in Formula II.

The present invention also provides a method for preparing the compound shown in Formula II as described above, which comprises the following steps: in a solvent, in the presence of a base and a condensing agent, subjecting the compound shown in Formula III to a condensation reaction as shown below to obtain the compound shown in Formula II;

wherein *, ^Ra , ^Ra ', R' and R" are as defined above; and ^Ra and ^Ra ' are the same, and R' and R" are the same.

The conditions and operations of the preparation method can be as described in any of the above schemes.

The present invention also provides a compound as shown in Formula II,

wherein *, ^Ra , ^Ra ', R' and R" are as defined above.

In one embodiment of the present invention, the compound as shown in Formula II is any of the following structures, isomers thereof or mixtures thereof:

In the present invention, the following definitions are used:

Unless otherwise indicated, the following definitions used herein shall apply. For purposes of the present invention, chemical elements are consistent with the Periodic Table of the Elements, CAS version, and Handbook of Chemistry and Physics, 75th edition, 1994. In addition, general principles of organic chemistry can be found in "Organic Chemistry", Thomas Sorrell, University Science Books, Sausalito: 1999, and "March's Advanced Organic Chemistry" by Michael B. Smith and Jerry March, John Wiley & Sons, New York: 2007, the entire contents of which are incorporated herein by reference.

In this specification, groups and substituents thereof can be selected by those skilled in the art to provide stable structural moieties and compounds. When substituents are described by conventional chemical formulas written from left to right, the substituents also include chemically equivalent substituents obtained when the structural formula is written from right to left.

Certain chemical groups defined herein are preceded by a shorthand notation to indicate the total number of carbon atoms present in the group. For example, _C1 - _C6 alkyl refers to an alkyl group as defined below having a total of 1, 2, 3, 4, 5 or 6 carbon atoms. The total number of carbon atoms in the shorthand notation does not include carbons that may be present in substituents of the group.

As used herein, numerical ranges defined in substituents such as 0 to 4, 1-4, 1 to 3, etc. indicate integers within the range, such as 1-6 is 1, 2, 3, 4, 5, 6.

用于描绘基团部分或取代基与核心或主链结构连接点处的键。According to the common practice in the art, the structural formula used herein is

Used to delineate the bond at the point of attachment of a radical moiety or substituent to the core or backbone structure.

According to the common practice in the art, "-" at the end of a group means that the group is connected to other fragments in the molecule through this site. For example, CH ₃ -C(=O)- refers to acetyl.

The term "one or more" or "one or more than two" means 1, 2, 3, 4, 5, 6, 7, 8, 9 or more.

The term "comprising" is an open expression, that is, including the contents specified in the present invention but not excluding other contents.

The term "substituted" means that any one or more hydrogen atoms on a particular atom are replaced by a substituent, including deuterium and hydrogen variants, as long as the valence state of the particular atom is normal and the substituted compound is stable.

In general, the term "substituted" means that one or more hydrogen atoms in a given structure are replaced by a specific substituent. Further, when the group is substituted by more than one of the substituents, the substituents are independent of each other, that is, the more than one substituents may be different or the same. Unless otherwise indicated, a substituent group may be substituted at each substitutable position of the substituted group. When more than one position in the given structural formula can be substituted by one or more substituents selected from a specific group, the substituents may be substituted at each position in the same or different manner.

In various parts of this specification, the substituents of the compounds disclosed in the present invention are disclosed according to the group type or range. It is particularly pointed out that the present invention includes each independent secondary combination of the members of these group types and ranges. For example, the term "C ₁ -C ₆ alkyl" or "C ₁ -C ₆ alkyl" specifically refers to the independently disclosed methyl, ethyl, C ₃ alkyl, C ₄ alkyl, C ₅ alkyl and C ₆ alkyl; "C _1-4 alkyl" specifically refers to the independently disclosed methyl, ethyl, C ₃ alkyl (i.e., propyl, including n-propyl and isopropyl), C ₄ alkyl (i.e., butyl, including n-butyl, isobutyl, sec-butyl and tert-butyl).

The term "halogen" refers to fluorine, chlorine, bromine or iodine.

The term "alkoxy" refers to a group ^-ORX , wherein ^RX is alkyl as defined above.

As used herein, the term "alkyl" refers to a straight or branched saturated hydrocarbon chain, such as a straight or branched saturated hydrocarbon chain containing 1 to 20 carbon atoms. The term " _Cx - _Cy alkyl" refers to a straight or branched saturated hydrocarbon containing x to y carbon atoms. For example, " _C1 - _C8 alkyl" refers to a straight or branched saturated hydrocarbon containing 1 to 8 carbon atoms. Representative examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, n-octyl, n-nonyl, and n-decyl.

As used herein, the term "cycloaliphatic" refers to a carbocyclic ring system containing 3 to 10 carbon atoms, zero heteroatoms, saturated or unsaturated (non-aromatic rings), which may be a monocyclic or bridged ring. Examples of saturated monocyclic ring systems ("cycloalkyl") include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Saturated bridged ring carbocyclic ring systems may contain one or two alkylene bridges, each alkylene bridge comprising one, two, or three carbon atoms, each bridge connecting two non-adjacent carbon atoms of the ring system. Representative examples of such bridged cycloalkyl carbocyclic ring systems include, but are not limited to, bicyclo[1.1.1]pentane, bicyclo[3.1.1]heptane, bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, bicyclo[3.2.2]nonane, bicyclo[3.3.1]nonane, bicyclo[4.2.1]nonane, tricyclo[3.3.1.0 3,7]nonane (octahydro-2,5-methylenepentalene or noradamantane), and tricyclo[3.3.1.1 3,7]decane (adamantane). Unsaturated monocyclic carbocyclic ring systems (e.g., "cycloalkenyl") may contain an olefinic bond, have four to ten carbon atoms, and zero heteroatoms. "Cycloalkenyl" of a four-membered ring system has one double bond, "cycloalkenyl" of a five- or six-membered ring system has one or two double bonds, "cycloalkenyl" of a seven- or eight-membered ring system has one, two or three double bonds, and "cycloalkenyl" of a nine- or ten-membered ring system has one, two, three or four double bonds. Representative examples of unsaturated monocyclic carbocyclic ring systems include, but are not limited to, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl and cyclooctenyl. Unsaturated monocyclic "cycloalkenyl" may contain one or two alkylene bridges, each alkylene bridge comprising one, two or three carbon atoms, each bridge connecting two non-adjacent carbon atoms of the ring system. Representative examples of unsaturated bridged ring carbocyclic ring systems containing olefinic bonds include, but are not limited to, bicyclo[2.2.1]hept-2-ene, 4,5,6,7-tetrahydro-3aH-indene, octahydronaphthyl and 1,6-dihydro-pentalene. Monocyclic and bridged ring "cycloaliphatic" (eg, "cycloalkyl," "cycloalkenyl") groups can be attached to the parent molecular moiety through any substitutable atom contained within the ring systems.

The term "heterocycloalkyl" as used herein refers to a cyclic group having a specified number of ring atoms (e.g., 5-10 members), a specified number of heteroatoms (e.g., 1, 2, or 3), a specified heteroatom type (one or more of N, O, and S), which is a monocyclic, bridged, or spirocyclic ring, and each ring is saturated. Heterocycloalkyl includes, but is not limited to, azetidinyl, tetrahydropyrrolyl, tetrahydrofuranyl, morpholinyl, piperidinyl, and the like.

The term "heteroaryl" as used herein refers to a cyclic group having a specified number of ring atoms (e.g., 5-10 members), a specified number of heteroatoms (e.g., 1, 2, or 3), a specified heteroatom species (one or more of N, O, and S), which is monocyclic or polycyclic, and at least one ring has aromaticity (in accordance with Huckel's rule). Heteroaryl is connected to other fragments in the molecule through a ring having aromaticity or a ring without aromaticity. Heteroaryl includes, but is not limited to, furanyl, pyrrolyl, thienyl, pyrazolyl, imidazolyl, oxazolyl, thiazolyl, pyridyl, pyrimidinyl, indolyl, etc.

The term "solvate" refers to a substance formed by the combination of a compound of the present invention and a stoichiometric or non-stoichiometric solvent. The solvent molecules in the solvate may exist in an ordered or non-ordered arrangement. The solvent includes, but is not limited to, water, methanol, ethanol, etc.

The term "pharmaceutically acceptable" means that salts, solvents, excipients, etc. are generally non-toxic, safe, and suitable for use by patients. The "patient" is preferably a mammal, more preferably a human.

The term "pharmaceutically acceptable salt" refers to a salt prepared from a compound of the present invention and a relatively nontoxic, pharmaceutically acceptable acid. When the compound of the present invention contains a relatively basic functional group, an acid addition salt can be obtained by contacting a neutral form of such compound with a sufficient amount of a pharmaceutically acceptable acid in a pure solution or a suitable inert solvent. The pharmaceutically acceptable acid includes an inorganic acid, including but not limited to hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, carbonic acid, bicarbonate, phosphoric acid, monohydrogen phosphate, dihydrogen phosphate, phosphorous acid, sulfuric acid, hydrogen sulfate, and the like. The pharmaceutically acceptable acid includes organic acids, including but not limited to acetic acid, trifluoroacetic acid, propionic acid, oxalic acid, isobutyric acid, maleic acid, malonic acid, benzoic acid, succinic acid, suberic acid, fumaric acid, lactic acid, mandelic acid, phthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, citric acid, salicylic acid, tartaric acid, methanesulfonic acid, isonicotinic acid, acid citric acid, oleic acid, tannic acid, pantothenic acid, bitartrate, ascorbic acid, gentisic acid, fumaric acid, gluconic acid, sugar acid, formic acid, ethanesulfonic acid, pamoic acid (i.e., 4,4'-methylene-bis(3-hydroxy-2-naphthoic acid)), amino acids (e.g., glutamic acid, arginine), etc. When the compound of the present invention contains a relatively basic functional group, it can be converted into an acid addition salt. For details, see Berge et al., "Pharmaceutical Salts", Journal of Pharmaceutical Science 66: 1-19 (1977), or Handbook of Pharmaceutical Salts: Properties, Selection, and Use (P. HeinrichStahl and Camille G. Wermuth, ed., Wiley-VCH, 2002).

The "pharmaceutically acceptable salt" and "solvate" in the term "pharmaceutically acceptable salt solvate" as described above refer to substances formed by combining the compounds of the present invention with 1. relatively non-toxic, pharmaceutically acceptable acids or bases prepared 2. stoichiometric or non-stoichiometric solvents.

As used herein, the terms "part", "moiety", "chemical moiety", "group", "chemical group" refer to a specific fragment or functional group in a molecule. A chemical moiety is generally considered to be a chemical entity embedded in or attached to a molecule.

When a substituent is listed without indicating the atom through which it is attached to a compound included in the chemical formula but not specifically mentioned, such a substituent may be bonded via any atom thereof. Combinations of substituents and/or variations thereof are permissible only if such combinations result in stable compounds.

When there is no explicit indication of substitution in the listed groups, such groups are only unsubstituted. For example, when "C ₁ -C ₄ alkyl" is not preceded by "substituted or unsubstituted", it only refers to "C ₁ -C ₄ alkyl" itself or "unsubstituted C ₁ -C ₄ alkyl".

In various parts of the present invention, linking substituents are described. When the structure clearly requires a linking group, the Markush variable listed for that group should be understood as a linking group. For example, if the structure requires a linking group and the Markush group definition for that variable lists "alkyl" or "aryl", it should be understood that the "alkyl" or "aryl" represents an alkylene group or an arylene group, respectively, that is connected.

In some specific structures, when an alkyl group is clearly indicated as a linking group, the alkyl group represents a linked alkylene group, for example, the C ₁ -C ₆ alkyl in the group “halo-C ₁ -C ₆ alkyl” should be understood as C ₁ -C ₆ alkylene.

Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter belongs. If there are multiple definitions for a term, the definition herein shall prevail.

It should be understood that the singular forms used in the present invention, such as "a", include plural references unless otherwise specified. In addition, the term "comprising" is an open limitation and not a closed form, that is, including the contents specified in the present invention, but not excluding other aspects.

Unless otherwise specified, the present invention adopts conventional methods of mass spectrometry and elemental analysis, and each step and condition can refer to conventional operating steps and conditions in the art.

Unless otherwise indicated, the present invention adopts standard nomenclature and standard laboratory procedures and techniques of analytical chemistry, organic synthetic chemistry and optics. In some cases, standard techniques are used for chemical synthesis, chemical analysis, and light emitting device performance testing.

In addition, it should be noted that, unless otherwise clearly indicated, the description method "... independently is" used in the present invention should be understood in a broad sense, meaning that the individuals described are independent of each other and can independently be the same or different specific groups. In more detail, the description method "... independently is" can mean that in different groups, the specific options expressed by the same symbols do not affect each other; it can also mean that in the same group, the specific options expressed by the same symbols do not affect each other.

On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

The reagents and raw materials used in the present invention are commercially available.

The positive and progressive effect of the present invention is that the diketopiperazine compounds provided by the present invention can be used as self-assembled drug-loaded microspheres to achieve effective drug delivery.

DETAILED DESCRIPTION

The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

Example 1 Synthesis of Compounds S1 to S18

Compounds S1 to S18 were synthesized by the following general formula:

Step 1: Dehydration cyclization reaction: 36 g of ε-benzyloxycarbonyl-L-lysine, 59 g of m-cresol, and 6 g of phosphorus pentoxide were added to a conical flask and heated to 200°C. Water was distilled off during the reaction, and then the reactants were cooled in a mixed solution of water and sodium hydroxide (10:1) to form a precipitate. The precipitate was separated and washed with 36 ml of ethanol, and then filtered to obtain 24.8 g of the crude product of the intermediate (2S,5S)-2,5-bis[4-(N-benzyloxycarbonyl)aminobutyl]-3,6-diketopiperazine. The crude product was heated (100°C) in 120 ml of glacial acetic acid solution, and then 36 ml of pure water was added to cool it. The crystals were then rinsed with 60 ml of glacial acetic acid solution to obtain 13.5 g of a refined product of the intermediate (2S,5S)-2,5-bis[4-(N-benzyloxycarbonyl)aminobutyl]-3,6-diketopiperazine (Compound 1).

Step 2: Hydrogenation reaction: 13.5 g of the product from the previous step was dissolved in 60 ml of glacial acetic acid solution, and a catalyst (10% palladium/carbon) was added to carry out a hydrogenation reaction in a reactor filled with hydrogen. The obtained mixed solution was cooled and filtered. The filtrate was then distilled to remove the glacial acetic acid component, and the acetate of (2S,5S)-2,5-bis(4-aminobutyl)-3,6-diketopiperazine (Compound 2) was obtained.

MS: 257 (M+H).

Step 3:

Condensation reaction: Dissolve the product from the previous step in DMF, add two equivalents of monocarboxylic acid (the structure of the monocarboxylic acid compound is shown in Table 1), two equivalents of triethylamine and an equivalent of HATU, and carry out the condensation reaction at room temperature. After the liquid phase detection shows that the raw material disappears, add water, and then separate the obtained solid material.

The solid crude product of the condensation product is obtained. Glacial acetic acid is added to the obtained solid crude product, and then water is added to cool it. After that, the crystals are washed with glacial acetic acid solution to obtain the condensation product (Compound I1-18).

Step 4: Saponification reaction: The condensation product obtained in the previous step was added to a mixed solution of methanol and 4 equivalents of sodium hydroxide (the volume mass ratio of methanol to sodium hydroxide was 10 mL/g) and heated to 70°C, then filtered and cooled to room temperature by adding glacial acetic acid. The solid matter was separated and washed with water to obtain a crude product of compound (S1-18).

Step 5: Recrystallization: Add trifluoroacetic acid to the crude target molecule obtained in the previous step and heat to 90°C. Filter the mixture, cool the filtrate, add glacial acetic acid, and further cool it. Separate the solid material and rinse it with methanol, then rinse it with purified water, and dry it to obtain compound (S1-18).

The structural formula and mass spectrum data of the monocarboxylic acid and the prepared compound I1-18 are shown in Table 1.

The structures of the prepared compounds S1 to S18 are shown in Table 2.

Table 2

Structural identification data of compound S1-18:

Compound S1: ¹ H NMR (400 MHz, DMSO) δ 1.24～1.54 (m, 8H), 1.77～1.78 (m, 4H), 3.02～3.06 (m, 4H), 3.98～3.99 (m, 2H), 8.25～8.26 (s, 2H), 8.72～8.99 (m, 8H), 10.01～12.17 (br, 2H). ESI, 555 (M+H).

Compound S2: ¹ H NMR (400 MHz, DMSO) δ 1.21～1.22 (m, 4H), 1.47～1.79 (m, 16H), 2.98～3.02 (m, 4H), 3.99～4.00 (m, 2H), 8.01～8.01 (s, 2H), 8.25～8.26 (s, 2H), 11.00～13.17 (br, 2H). ESI, 503 (M+Na).

Compound S3: ¹ H NMR (400 MHz, DMSO) δ 1.23-1.53 (m, 8H), 1.76-1.77 (m, 4H), 3.18-3.19 (m, 4H), 3.54-3.56 (m, 4H), 3.98-3.99 (m, 2H), 5.86 (s, 2H), 6.29 (s, 2H), 8.26-8.41 (s, 4H), 12.20-12.22 (br, 2H). ESI, 481 (M+H).

Compound S4: ¹ H NMR (400MHz, DMSO) δ1.23～1.25(m,4H), 1.50～1.75(m,12H), 2.70～2.80(m,4H), 3.17～3.18(m,4H), 3.33 ~3.34(m,4H),3.98~3.99(m,2H),6.06(s,2H),6.20(s,2H),8.01(s,2H),8.25(s,2H),12.01~12.14(br ,2H).ESI,607(M+Na).

Compound S5: ¹ H NMR (400MHz, DMSO) δ0.97～0.98(m,6H), 1.24～1.78(m,12H), 1.99～2.23(m,10H), 2.99～3.01(m,4H), 3.98 ~3.99(m,2H),7.70(s,2H),8.27(s,2H),11.60~11.80(br,2H).ESI,513(M+H).

Compound S6: ¹ H NMR (400 MHz, DMSO) δ 1.20-1.25 (m, 4H), 1.40-1.81 (m, 24H), 2.61-2.69 (m, 4H), 3.17-3.18 (m, 4H), 3.99-4.00 (m, 2H), 8.00 (s, 2H), 8.25 (s, 2H), 12.00-12.13 (br, 2H). ESI, 565 (M+H).

Compound S7: ¹ H NMR (400MHz, DMSO) δ1.24～1.25(m,4H), 1.39～1.80(m,12H), 1.99～2.26(m,8H), 3.00～3.01(m,4H), 3.99 ~4.00(m,2H),7.99(s,2H),8.02(s,2H),13.80~13.85(br,2H).ESI,509(M+H).

Compound S8: ¹ H NMR (400 MHz, DMSO) δ 1.25～1.26 (m, 4H), 1.50～1.52 (m, 4H), 1.76～2.21 (m, 16H), 3.02～3.03 (m, 4H), 3.99～4.00 (m, 2H), 8.01 (s, 2H), 8.04 (s, 2H), 12.0～12.02 (br, 2H). ESI, 533 (M+H).

Compound S9: ¹ H NMR (400MHz, DMSO) δ1.24～1.25(m,4H), 1.45(s,12H), 1.52～1.53(m,4H), 1.76～1.77(m,4H), 3.02～3.03 (m,4H),3.98～3.99(m,2H),8.00(s,2H),8.27(s,2H),13.81～13.85(br,2H).ESI,485(M+H).

Compound S10: ¹ H NMR (400 MHz, DMSO) δ 1.24-1.25 (m, 4H), 1.53-1.54 (m, 4H), 1.76-1.77 (m, 4H), 2.08-2.35 (m, 8H), 2.81-2.90 (m, 4H), 3.17-3.18 (m, 4H), 3.99-4.00 (m, 2H), 5.64-5.68 (m, 4H), 8.01 (s, 2H), 8.25 (s, 2H), 12.14-12.16 (br, 2H). ESI, 561 (M+H).

Compound S11: ¹ H NMR (400 MHz, DMSO) δ 1.23～1.24 (m, 4H), 1.33 (s, 12H), 1.52～1.53 (m, 4H), 1.76～1.77 (m, 4H), 2.38 (s, 4H), 3.02～3.03 (m, 4H), 3.96～3.99 (m, 2H), 8.01 (s, 2H), 8.26 (s, 2H), 13.13～13.14 (br, 4H). ESI, 535 (M+Na).

Compound S12: ¹ H NMR (400 MHz, DMSO) δ 1.24-1.25 (m, 4H), 1.49-1.84 (m, 12H), 2.18-2.23 (m, 4H), 3.17-3.19 (m, 4H), 3.99-4.00 (m, 2H), 8.01 (s, 2H), 8.25 (s, 2H), 12.12-12.13 (br, 2H). ESI, 503 (M+Na).

Compound S13: ¹ H NMR (400MHz, DMSO) δ1.24～1.25(m,4H), 1.52～1.53(m,4H), 1.76～1.84(m,10H), 2.06～2.08(m,4H), 2.32 ~2.34(m,4H),3.18~3.19(m,4H),3.99~4.00(m,2H),4.44~4.46(m,2H),8.01(s,2H),8.32~8.34(m,4H) ,12.00～12.01(br,2H).ESI,599(M+H).

Compound S14: ¹ H NMR (400 MHz, DMSO) δ 1.25-1.26 (m, 4H), 1.53-1.54 (m, 4H), 1.76-1.73 (m, 10H), 2.10-2.61 (m, 4H), 3.18-3.19 (m, 4H), 3.99-4.00 (m, 2H), 4.08-4.09 (m, 2H), 8.01 (s, 2H), 8.30 (s, 4H), 12.59-13.01 (br, 2H). ESI, 571 (M+H).

Compound S15: ¹ H NMR (400MHz, DMSO) δ1.24～1.25(m,4H), 1.53～1.54(m,4H), 1.76～1.77(m,4H), 3.07～0.08(m,4H), 3.99 ~4.00(m,4H),8.06~8.07(m,2H),8.24~8.26(d,2H),8.60~8.61(m,2H),9.13~9.14(m,2H),12.15~12.25(br, 2H).ESI,555(M+H).

Compound S16: ¹ H NMR (400 MHz, DMSO) δ 1.24-1.25 (m, 4H), 1.53-1.54 (m, 4H), 1.76-1.77 (m, 4H), 3.06-3.07 (m, 4H), 3.98-3.99 (m, 2H), 8.09-8.10 (d, 2H), 8.25-8.50 (m, 6H), 12.10-12.15 (br, 2H). ESI, 565 (M+H).

Compound S17: ¹ H NMR (400 MHz, DMSO) δ 1.25-1.26 (m, 4H), 1.53-1.54 (m, 4H), 1.77-1.78 (m, 4H), 3.04-3.05 (m, 4H), 3.99-4.06 (m, 6H), 6.36 (s, 2H), 8.27 (s, 2H), 13.00-13.01 (br, 2H). ESI, 459 (M+H).

Compound S18: ¹ H NMR (400MHz, DMSO) δ1.24～1.25(m,4H), 1.54～1.55(m,4H), 1.77～1.78(m,4H), 2.48～2.49(m,4H), 3.05 ~3.06(m,4H),63~3.66(m,4H),3.99~4.00(m,2H),6.01~6.02(m,4H),8.26(s,2H),12.10~12.13(br,2H) .ESI,487(M+H).

Example 2 Evaluation of drug loading

Experimental purpose: Using Dolutegravir (hereinafter referred to as Dol) as a model drug, a preliminary study on the drug loading capacity of FDKP and its derivatives was conducted.

Experimental method: accurately weigh 100 mg of FDKP or its derivative, add 15 mL of 1% ammonia water (v/v) to dissolve, and filter to remove insoluble substances; accurately weigh 70 mg of dolutegravir, add 1 mL of aqueous solution to dissolve, and add dropwise to the FDKP solution under magnetic stirring, and continue to adjust the pH to 5.0 with 10% glacial acetic acid aqueous solution (v/v), precipitate solid, filter, wash and dry to obtain Dol-FDKP-Der.

The solution obtained in the previous step is dissolved in an ammonium acetate solution, the pH is adjusted to completely dissolve, and the insoluble matter is removed by filtering the membrane. Then, the content of dolutegravir is detected by HPLC through area comparison.

The HPLC test method is as follows:

Chromatographic column: Ultimate XB-C18 (4.6×150mm, 3μm)

Flow rate: 1.0ml/min

Wavelength: 230nm Column temperature: 25℃

Mobile phase A: 0.1% phosphoric acid

Mobile phase B: acetonitrile

Experimental results: drug loading data results

Table 3

Compound No. % FDKP 44.1 S1 77.5 S2 52.4 S3 49.4 S4 38.1 S5 50.0 S6 67.1 S7 56.2 S8 55.4 S9 55.0 S10 65.2 S11 48.8 S12 56.2 S13 24.7 S14 33.7 S15 75.5 S16 62.9 S17 49.2 S18 47.7

Example 3 Cytotoxicity

1. Experimental Purpose

The toxicity of FDKP and its derivatives on mouse fibroblasts (NIH/3T3) was tested.

2. Test materials:

Reagents: FDKP and its derivatives, MTT, DMSO, DEME medium, gibico serum, etc.

Equipment: 96-well plates, EP tubes, centrifuge tubes, etc.

3. Experimental steps

1. Preparation of FDKP and derivative solutions

Accurately weigh 15 mg of FDKP or its derivative and dissolve it in 3 ml of 5% basal culture medium to prepare an initial solution of 5 mg/ml, and continue to dilute it with 5% basal culture medium to 2.5 mg/ml, 1.25 mg/ml, 0.625 mg/ml, 0.313 mg/ml, 0.156 mg/ml, 0.078 mg/ml, and 0.039 mg/ml.

2. MTT solution preparation

Weigh 10 mg of MTT and dissolve it in 2 ml of PBS solution to obtain an MTT solution with a concentration of 5 mg/ml.

3. Specific test steps

3T3 cells were diluted to an appropriate concentration, seeded in a 96-well plate at a density of 5000 cells per well (N=6), and cultured at 37°C and 5% CO2 for 12 hours.

Subsequently, the culture medium was removed, and 100 μl of culture medium containing different concentrations of FDKP or derivatives was added to each well, and the cells were cultured for 24 hours.

The culture medium of each well was removed, and 100ul of fresh culture medium and 10ul of MTT solution were added, and the cells were cultured for another 4 hours at 37°C and 5% _CO2 .

Then, the solution in the wells was removed, and 150ul of DMSO was added, and the crystals were fully dissolved by shaking at room temperature. The OD value of each group was recorded at 490nm using an ELISA reader.

Cell viability was calculated according to the following formula:

Cell viability percentage (%) = [(OD experimental group - OD blank group) / (OD control group - OD blank group)] * 100%.

Table 4 Cytotoxicity test results

Claims (15)

1. A diketopiperazine compound as shown in formula I or a pharmaceutically acceptable salt thereof,

Wherein, ^Ra and Ra ^' are independently selected from the following groups which are unsubstituted or substituted by one or more ^R4 : _-C1 - _C6 alkylene-,

-N(R ² )R ³ -, -5-10 membered heteroaryl-, -3-12 membered cycloaliphatic- and -3-7 membered heterocycloalkyl-; the heteroatoms in the -5-10 membered heteroaryl- are selected from one or more of N, O and S, and the number of heteroatoms is 1-4; the heteroatoms in the -3-7 membered heterocycloalkyl- are selected from one or more of N, O, S, S(=O) and S(=O) ₂ , and the number of heteroatoms is 1-3; when there are multiple substituents, they may be the same or different; R ⁴ is selected from C ₁ -C ₆ alkyl, C ₁ -C ₆ alkyl-O-, C ₁ -C ₆ alkyl substituted by one or more halogens, and -NHC(=O)-R ⁵ ; ^R1 and ^R3 are independently _-C1 - _C6 alkylene-; R ² and R ⁵ are independently selected from H or C ₁ -C ₆ alkyl; The carbon atom with "*" indicates that when it is a chiral carbon atom, it is in S configuration, R configuration or a mixture thereof. 2. The diketopiperazine compound or a pharmaceutically acceptable salt thereof as shown in formula I according to claim 1, characterized in that the diketopiperazine compound or a pharmaceutically acceptable salt thereof as shown in formula I satisfies one or more of the following conditions: (1) When ^Ra and Ra ^' are independently unsubstituted or substituted by one or more ^R4 with _-C1 - _C6 alkylene-, the _-C1 - _C6 alkylene- is _{independently -C1} - _C4 alkylene-, and the _-C1 - _C4 alkylene- is preferably -methylene-, _-CH2CH2- , -(CH( _CH3 )) _- , -CH2CH2CH2- _, - _{( C} (CH3) ₂ )-, _{-CH2CH2CH2CH2- ,} -( _CH ( _{CH3 )} ) _CH2CH2- or _-CH2CH ( _CH3 ) _CH2- , for _{example -methylene- , -CH2CH2-} or _{-CH2CH2CH2- ;} (2) When ^Ra and Ra ^' are independently -5-10 membered heteroaryl- which is unsubstituted or substituted by one or more ^R4 , the -5-10 membered heteroaryl- is -5-6 membered heteroaryl-, wherein the heteroatom is selected from one or more of N, O and S, the number of heteroatoms is 1-2, preferably -pyridyl-, -thienyl-, for example

(3) When ^Ra and Ra ^' are independently unsubstituted or substituted by one or more ^R4 -3-12-membered cycloaliphatic group, the -3-12-membered cycloaliphatic group is -3-7-membered cycloalkyl group or -4-7-membered cycloalkenyl group; the -3-7-membered cycloalkyl group is preferably -cyclopropyl-, -cyclobutyl-, -cyclopentyl-, -cyclohexyl- or -bicyclo[1.1.1]pentyl-, for example

The -4-7 membered cycloalkenyl- is preferably -cyclopropenyl-, -cyclobutenyl-, -pentenyl-, -cyclohexenyl-, -cycloheptenyl-, for example

(4) When ^R1 and ^R3 are independently _-C1 - _C6 alkylene-, the _-C1 - _C6 alkylene- is independently _-C1 - _C4 alkylene-, and the _-C1 - _C4 alkylene- is preferably -methylene-, _-CH2CH2- , -(CH( _{CH3 ) ) -} , _-CH2CH2CH2- , -(C ₍ CH3) _{2 )} -, _{-CH2CH2CH2CH2-} , -( _CH ( _CH3 )) _CH2CH2- or _{-CH2CH ( CH3 ) CH2-} , for example -methylene- _{or -CH2CH2-} ; (5) When ^R2 and ^R5 are independently _C1 - _C6 alkyl, the _C1 - _C6 alkyl is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, such as methyl; (6) When ^R4 is _C1 - _C6 alkyl, _C1 - _C6 alkyl-O-, or C1- _C6 alkyl substituted by one or more halogens, the C1-C6 alkyl in the _{C1 - C6} alkyl, _C1 - _C6 alkyl-O-, or _{C1 - C6} alkyl substituted by one or more halogens is independently _C1 - _C4 alkyl, and _{the C1-C4 alkyl is} preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, such as methyl; (7) When R ⁴ is a C ₁ -C ₆ alkyl group substituted by one or more halogens, the number of the halogens is 1-3; (8) When R ⁴ is a C ₁ -C ₆ alkyl group substituted by one or more halogens, the halogens are fluorine, chlorine, bromine or iodine, for example, fluorine or chlorine; (9) ^Ra and Ra ^' are independently selected from _-C1 - _C6 alkylene- substituted by one or _{more C1} - _C6 alkyl, -C1- _C6 alkylene- substituted by one or more -NHC(=O) ^-R5 ,

-N(R ² )R ³ -, -5- to 10-membered heteroaryl-, and -3- to 12-membered cycloaliphatic-; (10) The connection mode of -N(R ² )R ³ - is that the N atom is connected to the amide bond in Formula I, and R ³ is connected to the carboxyl group in Formula I; (11)

The connection mode is that the alkenyl group is connected to the amide bond in Formula I, and R ¹ is connected to the carboxyl group in Formula I; (12) R ² is selected from H; (13) R ⁴ is selected from C ₁ -C ₆ alkyl or -NHC(=O)-R ⁵ ; (14) R ⁵ is selected from C ₁ -C ₆ alkyl; (15) ^Ra and Ra ^' are the same or different, for example, the same; (16)

The configuration is

For example

3. The diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof according to claim 1, characterized in that: ^Ra and Ra ^' are independently selected from _-C1 - _C6 alkylene- substituted by one or more _C1 - _C6 alkyl, _-C1 - _C6 alkylene- substituted by one or more -NHC(=O) ^-R5 ,

-N(R ² )R ³ -, -5- to 10-membered heteroaryl-, and -3- to 12-membered cycloaliphatic-; ^R1 and ^R3 are independently _-C1 - _C6 alkylene-; ^R2 is H; R ⁵ is C ₁ -C ₆ alkyl; ^Ra and Ra ^' are the same. 4. The diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof according to claim 1, characterized in that: ^Ra and Ra ^' are independently

The connecting bond at position b is connected to the amide in Formula I, and the connecting bond at position c is connected to the carboxyl group in Formula I. 5. The diketopiperazine compound or a pharmaceutically acceptable salt thereof as described in any one of claims 1 to 4, characterized in that the diketopiperazine compound as described in formula I is selected from any of the following structures, isomers thereof or mixtures thereof:

6. A pharmaceutical composition comprising a diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof as described in any one of claims 1 to 5, and one or more active pharmaceutical ingredients. 7. The pharmaceutical composition according to claim 6, characterized in that the pharmaceutical composition satisfies one or more of the following conditions: (1) The pharmaceutical composition is a microsphere drug loading system; for example, the diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof as described in any one of claims 1 to 5 is a self-loading drug microsphere; (2) The weight percentage of the pharmaceutical active ingredient in the pharmaceutical composition is 10% to 90%, for example, 20% to 80%; (3) The active pharmaceutical ingredient is a cationic drug, anionic drug, hydrophilic/lipidic drug, peptide, protein or small molecule drug with an API molecular weight of 500-140,000 Da, such as insulin, dolutegravir or sildenafil; (4) The active ingredient of the drug is a poorly soluble drug; (5) The pharmaceutical composition further comprises a pharmaceutically acceptable excipient. 8. A method for preparing the pharmaceutical composition according to claim 6 or 7, characterized in that it comprises the following steps: adding a solution containing the pharmaceutical active ingredient to an alkaline solution containing the diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof, and adjusting the pH to precipitate a solid to obtain the pharmaceutical composition; The mass ratio of the active pharmaceutical ingredient to the diketopiperazine compound or its pharmaceutically acceptable salt as shown in Formula I can be 7:10; the alkaline solution can be obtained by adding 1% ammonia water (v/v); the pH can be 5.0; the adjusted pH can be adjusted by adding 10% glacial acetic acid aqueous solution (v/v); the obtained pharmaceutical composition is preferably filtered, washed and then dried. 9. A use of a diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof as claimed in any one of claims 1 to 5 as a formulation excipient; for example, the diketopiperazine compound of formula I or a pharmaceutically acceptable salt thereof is used to form drug-loaded microspheres. 10. A method for preparing a diketopiperazine compound as shown in formula I according to any one of claims 1 to 5, comprising the following steps: subjecting a compound as shown in formula II to a saponification reaction as shown below in a solvent in the presence of a base to obtain the diketopiperazine compound as shown in formula I;

Wherein, *, ^Ra and Ra ^' are defined as any one of claims 1-5; R' and R" are independently _C1 - _C8 alkyl, and the _C1 - _C8 alkyl can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, such as methyl and tert-butyl. 11. The method for preparing the diketopiperazine compound of formula I according to claim 10, wherein the saponification reaction satisfies one or more of the following conditions: (1) The solvent is an alcohol solvent, such as methanol and/or ethanol; (2) The volume mass ratio of the solvent to the compound of Formula II is 1 mL/g-50 mL/g, for example 5 mL/g; (3) The base is an alkali metal hydroxide, such as sodium hydroxide and/or potassium hydroxide; (4) The volume mass ratio of the solvent to the base is 5 mL/g-20 mL/g, for example 10 mL/g; (5) The molar ratio of the base to the compound of formula II is 2:1-10:1, for example 4:1; The temperature of the saponification reaction shown in (6) is from room temperature to 80°C, for example, 60-70°C; (7) The preparation method further includes post-treatment and crystallization; the post-treatment may include the following steps: after the saponification reaction is completed, acid is added for neutralization to precipitate solids to obtain the diketopiperazine compound as shown in Formula I; the crystallization may include the following steps: filtering the mixture of the diketopiperazine compound as shown in Formula I and trifluoroacetic acid obtained after the post-treatment as described above, mixing the filtrate with glacial acetic acid, cooling to precipitate solids, filtering, and washing to obtain crystals of the diketopiperazine compound as shown in Formula I. 12. The method for preparing the diketopiperazine compound of formula I as claimed in claim 10, characterized in that: The preparation method further comprises the following steps: in a solvent, in the presence of a base and a condensing agent, subjecting the compound shown in formula III to a condensation reaction as shown below to obtain the compound shown in formula II;

wherein, *, ^Ra and Ra ^' are as defined in any one of claims 1 to 5, R' and R" are as defined in claim 10, and ^Ra and Ra ^' are the same, and R' and R" are the same. 13. The method for preparing the diketopiperazine compound of formula I according to claim 12, wherein the condensation reaction satisfies one or more of the following conditions: (1) The solvent is one or more of an amide solvent, a sulfoxide solvent, a halogenated hydrocarbon solvent and a cyclic ether solvent; the amide solvent may be N,N-dimethylformamide and/or N,N-dimethylacetamide; the sulfoxide solvent may be dimethyl sulfoxide; the halogenated hydrocarbon solvent may be dichloromethane; the cyclic ether solvent may be tetrahydrofuran; (2) The base is an organic base, such as triethylamine; (3) The molar ratio of the base to the compound of formula III is 1.5:1-3:1, for example 2:1-2.5:1; (4) the condensing agent is one or more of HATU, EDTA and HBTU, for example, HATU and/or EDTA; (5) The molar ratio of the condensing agent to the compound of formula III is 1.0:1-2:1, for example 1:1-1.5:1; (6) The molar ratio of the compound represented by Formula IV to the compound represented by Formula III is 2:1-1:1; (7) The condensation reaction temperature is from room temperature to 80°C, for example, 10-30°C; (8) The condensation reaction further includes post-treatment and crystallization; the post-treatment and crystallization may include the following steps: after the condensation reaction is completed, the filter cake obtained by filtration is crystallized in glacial acetic acid and water to precipitate a solid to obtain the compound shown in Formula II. 14. A method for preparing a compound of formula II, characterized in that it comprises the following steps: in a solvent, in the presence of a base and a condensing agent, subjecting a compound of formula III to a condensation reaction as shown below to obtain the compound of formula II;

wherein, *, ^Ra , and Ra ^" are defined as described in any one of claims 1 to 5, R' and R' are defined as described in claim 10, and ^Ra and ^Ra' are the same, and R' and R" are the same; The conditions and operations of the preparation method are as described in claim 12 or 13. 15. A compound as shown in formula II,

wherein, *, ^Ra , and Ra ^" are defined as described in any one of claims 1 to 5, R' and R' are defined as described in claim 10, and ^Ra and ^Ra' are the same, and R' and R" are the same; The compound shown in Formula II may be any of the following structures, isomers thereof or mixtures thereof: