AU2002257774A1 - Broadspectrum 2-(substituted-amino)-benzoxazole sulfonamide HIV protease inhibitors - Google Patents

Description

BROADSPECT UM 2-rSUBSTITUTED-AMINO)-BENZOXAZOLE SULFONAMIDE HIV PROTEASE INHIBITORS

The piresent invention relates to 2-(substituted-amino)-benzoxazole sulfonamides, their use as aspartic protease inhibitors, in particular as broadspectrum HIV protease inhibitors, processes for their preparation as well as pharmaceutical compositions and diagnostic kits comprising them. The present invention also concerns combinations of the present 2-(substituted-amino)-benzoxazole sulfonamides with another anti-retroviral agent. It further relates to their use r assays as reference compounds or as reagents.

The virus causing the acquired immunodeficiency syndrome (AIDS) is known by different names, including T-lymphocyte virus III (HTLN-III) or lymphadenopathy- associated virus (LAV) or AIDS-related virus (ARV) or human immunodeficiency virus (HIV). Up until now, two distinct families have been identified, i.e. HIV-1 and HIV-2. Hereinafter, HIV will be used to generically denote these viruses.

One of the critical pathways in a retro viral life cycle is the processing of polyprotein precursors by aspartic protease. For instance with the HIN virus the gag-pol protein is processed by HIN protease. The correct processing of the precursor polyproteins by the aspartic protease is required for the assembly of infectious virions, thus making the aspartic protease an attractive target for antiviral therapy. In particular for HIV treatment, the HIV protease is an attractive target.

HIN protease inhibitors (Pis) are commonly administered to AIDS patients in combination with other anti-HIN compounds such as, for instance nucleoside reverse transcriptase inhibitors (ΝRTIs), non-nucleoside reverse transcriptase inhibitors (ΝΝRTIs), nucleotide reverse transcriptase inhibitors (ΝtRTIs) or other protease inhibitors. Despite the fact that these antiretrovirals are very useful, they have a common limitation, namely, the targeted enzymes in the HIV virus are able to mutate in such a way that the known drugs become less effective, or even ineffective against these mutant HIV viruses. Or, in other words, the HIV virus creates an ever increasing resistance against the available drugs.

Resistance of retroviruses, and in particular the HIV virus, against inhibitors is a major cause of therapy failure. For instance, half of the patients receiving anti-HIN combination therapy do not respond fully to the treatment, mainly because of resistance of the virus to one or more drags used. Moreover, it has been shown that resistant virus is carried over to newly infected individuals, resulting in severely limited therapy options for these drug-naive patients. Therefore, there is a need in the art for new compounds for retrovirus therapy, more particularly for AIDS therapy. The need in the art is particularly acute for compounds that are active not only on wild type HIV virus, but also on the increasingly more common resistant HIV viruses.

Known antiretrovirals, often administered in a combination therapy regimen, will eventually cause resistance as stated above. This often may force the physician to boost the plasma levels of the active drugs in order for said antiretrovirals to regain effectivity against the mutated HIV viruses. The consequence of which is a highly undesirable increase in pill burden. Boosting plasma levels may also lead to an increased risk of non-compliance with the prescribed therapy. Thus, it is not only important to have compounds showing activity for a wide range of HIV mutants, it is also important that there is little or no variance in the ratio between activity against mutant HIV virus and activity against wild type HIN virus (also defined as fold resistance or FR) over a broad range of mutant HIN strains. As such, a patient may remain on the same combination therapy regimen for a longer period of time since the chance that a mutant HIN virus will be sensitive to the active ingredients will be increased.

Finding compounds with a high potency on the wild type and on a wide variety of mutants is also of importance since the pill burden can be reduced if therapeutic levels are kept to a minimum. One way of reducing this pill burden is finding anti-HIN compounds with good bioavailability, i.e. a favorable pharmacokinetic and metabolic profile, such that the daily dose can be minimized and consequently also the number of pills to be taken.

Another important characteristic of a good anti-HIN compound is that plasma protein binding of the inhibitor has minimal or even no effect on its potency.

Thus, there is a high medical need for protease inhibitors that are able to combat a broad spectrum of mutants of the HIN virus with little variance in fold resistance, have a good bioavailability and experience little or no effect on their potency due to plasma protein binding.

Up until now, several protease inhibitors are on the market or are being developed. One particular core structure (depicted below) has been disclosed in a number of references, such as, WO 95/06030, WO 96/22287, WO 96/28418, WO 96/28463,

WO 96/28464, WO 96/28465 and WO 97/18205. The compounds disclosed therein are described as retroviral protease inhibitors.

WO 99/67254 discloses 4-substituted-phenyl sulfonamides capable of inhibiting multi- drug resistant retro viral proteases .

Surprisingly, the 2-(substituted-amino)-benzoxazole sulfonamides of the present invention are found to have a favorable pharmacological and pharmacokinetic profile. Not only are they active against wild-type HIN virus, but they also show a broadspectrum activity against various mutant HIN viruses exhibiting resistance against known protease inhibitors.

The present invention concerns 2-(substitoted-amino)-benzoxazole protease inhibitors, having the formula

and N-oxides, salts, stereoisomeric forms, racemic mixtures, prodrugs, esters and metabolites thereof, wherein

Ri and R₈ are, each independently, hydrogen, C_1-6alkyl, C_2-6alkenyl, arylC_1-6alkyl,

C_3-7cycloalkyl, C_3-7cycloalkylC_1-6alkyl, aryl, Het¹, Het¹C_1-6alkyl, Het²,

Het²C_1-6alkyl;

Ri may also be a radical of formula

wherein R , R_10a and Rι₀ are, each independently, hydrogen, C_1- alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or C_3-7cycloalkyl, C_2-6alkenyl, C_2-6alkynyl or C_1- alkyl optionally substituted aminocarbony , mono- or di^i^al y am nocar ony , am nosu ony , hydroxy, cyano, halogen or amino optionally mono- or disubstituted where the substituents are each independently selected from Cι_ alkyl, aryl, arylCi^alkyl, C_3- cycloalkyl, C_3-7cycloalkylC_Malkyl, Het¹, Het², He^C^alkyl and Het^C_Mal yl; whereby R₉, R_10a and the carbon atoms to which they are attached may also form a C_3- cycloalkyl radical; R₉ may also be oxo; R_lla is hydrogen, C_2-6alkenyl, C_2-6alkynyl, C_3- cycloalkyl, aryl, aminocarbonyl optionally mono- or disubstituted, aminoC_1- alkylcarbonyloxy optionally mono- or disubstituted, C_1-4alkyloxycarbonyl, aryloxycarbonyl, Het y- carbonyl, Het²oxycarbonyl, aryloxycarbonylC^alkyl, arylC^alkyloxy- carbonyl, C_1- alkylcarbonyl, C_3-7cycloalkylcarbonyl, C_3-7cycloalkyl- C_3-7cycloalkylcarbonyloxy, carboxylCι- alkyl- carbonyloxy, C_1-4alkylcarbonyloxy, arylCι- alkylcarbqnyloxy, arylcarbonyloxy, aryloxycarbonyloxy, He^carbonyl, Het bonyloxy,

Het^Malkyloxycarbonyl, Het²carbonyloxy, Het²C_1- alkylcarbonyloxy, Het²C_1- alkyloxycarbonyloxy or C_1-4alkyl optionally substituted with aryl, aryloxy, Het², halogen or hydroxy; wherein the substituents on the amino groups are each independently selected from C_1- alkyl, aryl, arylCι_-4alkyl, C_3-7cycloalkyl, C_3-7cycloalkylC_Malkyl, Het¹, Het², He^C^alkyl and

Het²C_1-4alkyl; Rπ_b is hydrogen, C_3-7cycloalkyl, C_2- alkenyl, C _-6alkynyl, aryl, Het¹, Het² or C_1- alkyl optionally substituted with halogen, hydroxy, C_1- alkylS(=O)_t, aryl, C - cycloalkyl, Het , Het , amino optionally mono- or disubstituted where the substituents are each independently selected from C_hal y!, aryl, arylC_1-4alkyl, C_3- cycloalkyl, C_3-7cycloalkylC_1-4alkyl, Het¹, Het², Het^walkyl and Het²C_1-4alkyl; whereby Ri i_b maybe linked to the remainder of the molecule via a sulfonyl group; each independently, t is^'zero, 1 or 2; R₂ is hydrogen or C_1-6alkyl;

L is -C(=O)-, -O-C(=O)-, -NR₈-C(=O)-, -O-Cι_-6alkanediyl-C(=O)-,

-NR₈-Cι_-6alkanediyl-C(=O)-, -S(=O)₂-, -O-S(=O) -, -NR₈-S(=O)₂ whereby either the C(=O) group or the S(=O)₂ group is attached to the NR₂ moiety; whereby the Cι_-6aιkanediyl moiety is optionally substituted with aryl, Het , Het ;

R₃ is C_1-6alkyl, aryl, C₃.₇cycloalkyl,

R is hydrogen, carboxyl, aminocarbonyl, mono- or di(C_Malkyl)aminocarbonyl, C_3-7cycloalkyl, C_2-6alkenyl, C_2-6alkynyl, or Cι_-6alkyl optionally substituted with one or more substituents each independently selected from aryl, Het¹, Het², C₃. cycloalkyl, C_1- alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(Cι- alkyl)aminocarbonyl, aminosulfonyl, Cι- alkylS(=O)_t, hydroxy, cyano, halogen and amino optionally mono- or disubstituted where the substituents are each independently selected from

C_1-4alkyl, aryl, .arylC_1-4alkyl, C_3-7cyclo alkyl, Cs^cycloalkylCi^alkyl, Het¹, Het², Her'Ci^alkyl and Het²C_1-4alkyl; .

A is C_1-6alkanediyl, -C(=O)-, -C(=S , -S(=O)₂-, C_1-6alkanediyl-C(=O)-, C_1-6alkane- diyl-C(=S)- or Cι_-6alkanediyl-S(=O)₂-; whereby the point of attachment to the nitrogen atom is the Cι_-6alkanediyl group in those moieties containing said group;

R₅ is hydrogen, hydroxy, C_1-6alkyl, He^C^alkyl, Het²C_1-6alkyl, amino -ealkyl whereby the amino group may optionally be mono- or di-substituted with C_1- alkyl;

Rg is Ci-ealkyloxy, Het¹, Het y, Het², Hel^oxy, aryl, aryloxy or amino; and in case -A- is other than Ci-βalkanediyl then R₆ may also be Cι_-6alkyl, Het^ alkyl,

Het yCMalkyl, Het²Cι_-4alkyl, Het^oxyCi^alkyl, arylCi^alkyl, aryloxyCι_-4alkyl or aminoCι_-6alkyl; whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents each independently selected from C_1-4alkylcarbonyl, aryl, arylcarbonyl, aryloxycarbonyl, Het¹, Het², arylCι- alkyl, Het¹ C_halky! or

Het C] galkyl; and

-A-R₆ may also be hydroxyC_1-6alkyl;

R₅ and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het¹ or Het².

This invention also envisions the quaternization of the nitrogen atoms of the present compounds. A basic nitrogen can be quaternized with any agent known to those of ordinary skill in the art including, for instance, lower alkyl halides, dialkyl sulfates, long chain halides and aralkyl halides.

Whenever the term "substituted" is used in defining the compounds of formula (I), it is meant to indicate that one or more hydrogens on the atom indicated in the expression using "substituted" is replaced with a selection from the indicated group, provided that the indicated atom's normal valency is not exceeded, and that the substitution results in a chemically stable compound, i.e. a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture, and formulation into a therapeutic agent.

As used herein, the term "halo" or "halogen" as a group or part of a group is generic for fluoro, chloro, bromo or iodo.

The term "Cι- alkyl" as a group or part of a group defines straight and branched chained saturated hydrocarbon radicals having from 1 to 4 carbon atoms, such as, for example, methyl, ethyl, propyl, butyl and 2-methyl-propyl, and the like.

The term "C_1- alkyl" as a group or part of a group defines straight and branched chained saturated hydrocarbon radicals having from 1 to 6 carbon atoms such as the groups defined for C_1-4alkyl and pentyl, hexyl, 2-methylbutyl, 3-methylpentyl and the like. The term " -ealkanediyl" as a group or part of a group defines bivalent straight and branched chained saturated hydrocarbon radicals having from 1 to 6 carbon atoms such as, for example, methylene, ethan-l,2-diyl, propan-l,3-diyl, propan-l,2-diyl, butan- 1,4-diyl, pentan-l,5-diyl, hexan-l,6-diyl, 2-methylbutan-l,4-diyl, 3-methylpentan- 1,5-diyl and the like. The term "C_2-6alkenyl" as a group or part of a group defines straight and branched chained hydrocarbon radicals having from 2 to 6 carbon atoms containing at least one double bond such as, for example, ethenyl, propenyl, butenyl, pentenyl, hexenyl and the like. The term "C_2-6alkynyl" as a group or part of a group defines straight and branched chained hydrocarbon radicals having from 2 to 6 carbon atoms containing at least one triple bond such as, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl and the like.

The term "C_3- cycloalkyl" as a group or part of a group is generic to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl. The term "aryl" as a group or part of a group is meant to include phenyl and naphtyl which both may be optionally substituted with one or more substituents independently selected from C_halky!, optionally mono- or disubstituted aminoCi_-6alkyl, C_1-6alkyloxy, halogen, hydroxy, optionally mono- or disubstituted amino, nitro, cyano, haloC_1-6alkyl, carboxyl, C_1-6alkoxycarbonyl, C3- cycloalkyl, Het¹, optionally mono- or disubstituted aminocarbonyl, methylthio, methylsulfonyl, and phenyl optionally substituted with one or more substituents each independently selected from Cι-₆alkyl, optionally mono- or disubstituted armnoCι-₆alkyl„ Cι,₆alkyloxy, halogen, hydroxy, optionally mono- or disubstituted amino, nitro, cyano, haloC_1- alkyl, carboxyl, Ci-ealkoxycarbonyl, C_3-7cycloalkyl, Het¹, optionally mono- or disubstituted aminocarbonyl, methylthio and methylsulfonyl; whereby the optional substituents on any amino function are independently selected from C_1-6alkyl, optionally mono- or disubstituted aminoCi- ealkyl, Cι_-6alkyloxy-A-, Het y-A-, Het^ yC_Makyl-A-, phenyl-A-, phenyl-oxy-A-, phenyloxyC_1-4alkyl-A-, phenyl- C_1-6alkyl-A-, C_1-6alkyloxycarbonylaπιino-A-, amino-A-, aminoC_1-6alkyl and amino- Cι_-6alkyl-A- whereby each of the amino groups may optionally be mono- or where possible di-substituted with Ci^alkyl and whereby A is as defined above. An interesting subgroup in the definition of "aryl" as a group or part of a group includes phenyl and naphtyl which both may be optionally substituted with one or more substituents independently selected from C_1-6alkyl, C_1-6alkyloxy, halogen, hydroxy, optionally mono- or disubstituted amino, nitro, cyano, haloCι-6alkyl, carboxyl, . ₆alkoxycarbonyl, C_3- cycloalkyl, Het¹, optionally mono- or disubstituted aminocarbonyl, methylthio, methylsulfonyl, and phenyl optionally substituted with one or more substituents selected from C^aUcyl, d-βalkyloxy, halogen, hydroxy, optionally mono- or disubstituted amino, nitro, cyano, carboxyl, Ci. ₆alkoxycarbonyl, C3- cycloalkyl, Het¹, optionally mono- or disubstituted aminocarbonyl, methylthio and methylsulfonyl; whereby the optional substituents on any amino function are independently selected from Ci-βalkyl, Cι_-6alkyloxy-A-, Het¹- A-, Het'Ci-ealkyl, He^C^alkyl-A-, Het y-A-, HetVyC_3- akyl-A-, phenyl-A-, ρhenyl-oxy-A-, phenyloxyC alkyl-A-, phenylCι_-6alkyl-A-, C_1-6alkyloxycarbonyl- amino-A-, amino-A-, aminoCι_-6alkyl and aminoCi-_δalkyl-A- whereby each of the amino groups may optionally be mono- or where possible di-substituted with C_1-4alkyl and whereby A is as defined above. The term "haloCι_-6alkyl" as a group or part of a group is defined as Cι_-6alkyl substituted with one or more halogen atoms, preferably, chloro or fluoro atoms, more preferably fluoro atoms. Preferred haloCι_-6alkyl groups include for instance trifluoromethyl and diftuoromethyl. The term "Het " as a group or part of a group is defined as a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having preferably 3 to 14 ring members, more preferably 5 to 10 ring members and more preferably 5 to 8 ring members, which contains one or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur and which is optionally substituted on one or more carbon atoms by C_1-6alkyl, optionally mono- or disubstituted aminoCι_-6alkyl, Cμδalkyloxy, halogen, hydroxy, oxo, optionally mono- or disubstituted amino, nitro, cyano, haloCi-ealkyl, carboxyl, C]_-6alkoxycafbonyl, C_3- cyclo alkyl, optionally mono- or disubstituted aminocarbonyl, methylthio, methylsulfonyl, aryl and a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 14 ring members which contains one or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur and whereby the optional substituents on any amino function are independently selected from Cι_₆alkyl, optionally mono- or disubstituted aminoCι_-6alkyl, Cι_-6alkyloxy-A-, Het²-A-, He^Ci^alkyl, Het²Cι_-6alkyl-A- , Het²oxy-A-, aryl-A-, aryloxy-A-, arylCi-βalkyl-A-, C_1-6alkyloxycarbonylamino-A-, amino-A-, aminoCι_-6alkyl and aminoCι_-6alkyl-A- whereby each of the amino groups may optionally be mono- or where possible di-substituted with C_1- alkyl and whereby A is as defined above. An interesting subgroup in the definition of "Het¹" as a group or part of a group is defined as a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having preferably 3 to 12 ring members, more preferably 5 to 10 ring members and more preferably 5 to 8 ring members, which contains one or more heteroatom ring members selected from nitrogen, oxygen or sulfur and which is optionally substituted on one or more carbon atoms by Cι_-6alkyl, Cι_-6alkyloxy, halogen, hydroxy, oxo, optionally mono- or disubstituted amino, nitro, cyano, haloCι_-6alkyl, carboxyl, C_1-6alkoxycarbonyl, C_3- cycloalkyl, optionally mono- or disubstituted aminocarbonyl, methylthio, methylsulfonyl, aryl and a saturated or partially unsaturated monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members which contains one or more heteroatom ring members selected_. from nitrogen, oxygen or sulfur and whereby the optional substituents on any amino function are independently selected from Cι_-6alkyl, Cι_-6alkyloxy-A-, Het²-A-, Het²C_1-6alkyl, Het²Cι- ₆alkyl-A-, Het²oxy-A-, aryl-A-, aryloxy-A-, aryloxyC_1-4alkyl-A-, arylCi.δalkyl-A-, Ci_-6alkyloxycarbonylamino-A-, amino-A-, aminoC βalkyl and aminoC_1-6alkyl-A- whereby each of the amino groups may optionally be mono- or where possible di-substituted with C_1-4alkyl and whereby A is as defined above.

The term "Het " as a group or part of a group is defined as an aromatic monocyclic, bicyclic or tricyclic heterocycle having preferably 3 to 14 ring members, more preferably 5 to 10 ring members and more preferably 5 to 6 ring members, which contains one or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur and which is optionally substituted on one or more carbon atoms by Cι_-6alkyl, optionally mono- or disubstituted aminoCι_-6alkyl, Cι_-6alkyloxy, halogen, hydroxy, optionally mono- or disubstituted amino, nitro, cyano, haloCι.₆alkyl, carboxyl, Cι-6alkoxycarbonyl, C_3-7cycloalkyl, optionally mono- or disubstituted aminocarbonyl, methylthio, methylsulfonyl, aryl, Het¹ and an aromatic monocyclic, bicyclic or tricyclic heterocycle having 3 to 14 ring members; whereby the optional substituents on any amino function are independently selected from C^aUcyl, optionally mono- or disubstituted aminoCι_-6alkyl, Het y-A-, Het yCMakyl-A-, aryl-A-, aryloxy-A-, arylCι_-6alkyl-A-, Cι_-6alkyloxycarbonylamino-A-, amino-A-, aminoC_1-6alkyl and aminoCi-βalkyl-A- whereby each of the amino groups may optionally be mono- or where possible di-substituted with C_Malkyl and whereby A is as defined above.

An interesting subgroup in the definition of "Het²" as a group or part of a group is defined as an aromatic monocyclic, bicyclic or tricyclic heterocycle having preferably 3 to 12 ring members, more preferably 5 to 10 ring members and more preferably 5 to 6 ring members, which contains one or more heteroatom ring members selected from nitrogen, oxygen or sulfur and which is optionally substituted on one or more carbon atoms by Cι_-6alkyl, Cι_-6alkyloxy, halogen, hydroxy, optionally mono- or disubstituted amino, nitro, cyano, haloC_1-6alkyl, carboxyl, C_1-6alkoxycarbonyl, C3- cycloalkyl, optionally mono- or disubstituted aminocarbonyl, methylthio, methylsulfonyl, aryl, Het¹ arid an aromatic monocyclic, bicyclic or tricyclic heterocycle having 3 to 12 ring members; whereby the optional substituents on any amino function are independently selected from Het y-A-, aryl-A-, aryloxy-A-, aryloxyCι-₄alkyl-A-, arylC!- ₆alkyl-A-, Cι_₆alkyloxycarbonylamino-A-, amino-A-, aminoCι_-6alkyl and aminoCi;- ₆alkyl-A- whereby each of the amino groups may optionally be mono- or where possible di-substituted with C_1-4alkyl and whereby A is as defined above.

As used herein, the term (=0) forms a carbonyl moiety with the carbon atom to which it is attached. The term (=O) forms a sulfoxide with the sulfur to which it is attached.

The term (=O)₂ forms a sulfonyl to the sulfur to which it is attached.

As used herein, the term (=S) forms a thiocarbonyl moiety with the carbon atom to which it is attached.

As used herein before, the term "one or more" covers the possibility of all the available C-atoms, where appropriate, to be substituted, preferably, one, two or three.

When any variable (e.g. halogen or Ci^alkyl) occurs more than one time in any constituent, each definition is independent.

The term "prodrug" as used throughout this text means the pharmacologically acceptable derivatives such as esters, amides and phosphates, such that the resulting in vivo biotransformation product of the derivative is the active drug as defined in the compounds of formula (I). The reference by Goodman and Gilman (The Pharmacological Basis of Therapeutics, 8^th ed, McGraw-Hill, Int. Ed. 1992, "Biotransformation of Drugs", p 13-15) describing prodrugs generally is hereby incorporated. Prodrugs of a compound of the present invention are prepared by modifying functional groups present in the compound in such a way that the modifications are cleaved, either in routine manipulation or in vivo, to the parent compound. Prodrugs include compounds of the present invention wherein a hydroxy group, for instance the hydroxy group on the asymmetric carbon atom, or an amino group is bonded to any group that, when the prodrug is administered to a patient, cleaves to form a free hydroxyl or free amino, respectively.

Typical examples of prodrugs are described for instance in WO 99/33795,

WO 99/33815, WO 99/33793 and WO 99/33792 all incoφorated herein by reference.

Prodrugs are characterized by excellent aqueous solubility, increased bioavailability and are readily metabolized into the active inhibitors in vivo.

For therapeutic use, the salts of the compounds of formula (I) are those wherein the counterion is pharmaceutically or physiologically acceptable. However, salts having a pharmaceutically unacceptable counterion may also find use, for example, in the preparation or purification of a pharmaceutically acceptable compound of formula (I). All salts, whether pharmaceutically acceptable or not are included within the ambit of the present invention.

The pharmaceutically acceptable or physiologically tolerable addition salt forms which the compounds of the present invention are able to form can conveniently be prepared using the appropriate acids, such as, for example, inorganic acids such as hydrohalic acids, e.g. hydrochloric or hydrobromic acid; sulfuric; nitric; phosphoric and the like acids; or organic acids such as, for example, acetic, propanoic, hydroxyacetic, lactic, pyruvic, oxalic, malonic, succinic, maleic, fumaric, malic, tartaric, citric, methane- sulfonic, ethanesulfonic, benzenesulfonic, _/?-toluenesulfonic, cyclamic, salicylic, -aminosalicylic, pamoic and the like acids.

Conversely said acid addition salt forms can be converted by treatment with an appropriate base into the free base form.

The compounds of formula (I) containing an acidic proton may also be converted into their non-toxic metal or amine addition salt form by treatment with appropriate organic and inorganic bases. Appropriate base salt forms comprise, for example, the ammonium salts, the alkali and earth alkaline metal salts, e.g. the lithium, sodium, potassium, magnesium, calcium salts and the like, salts with organic bases, e.g. the benzathine, N-methyl, -D-glucamine, hydrabamine salts, and salts with a ino acids such as, for example, arginine, lysine and the like.

Conversely said base addition salt forms can be converted by treatment with an appropriate acid into the free acid form.

The term "salts" also comprises the hydrates and the solvent addition forms which the compounds of the present invention are able to form. Examples of such forms are e.g. hydrates, alcoholates and the like.

The N-oxide forms of the present compounds are meant to comprise the compounds of formula (I) wherein one or several nitrogen atoms are oxidized to the so-called N-oxide.

The present compounds may also exist in their tautomeric forms. Such forms, although not explicitly indicated in the above formula are intended to be included within the scope of the present invention.

The term stereochemically isomeric forms of compounds of the present invention, as used hereinbefore, defines all possible compounds made up of the same atoms bonded by the same sequence of bonds but having different three-dimensional structures which are not interchangeable, which the compounds of the present invention may possess. Unless otherwise mentioned or indicated, the chemical designation of a compound encompasses the mixture of all possible stereochemically isomeric forms which said compound may possess. Said mixture may contain all diastereomers and/or enantiomers of the basic molecular structure of said compound. All stereochemically isomeric forms of the compounds of the present invention both in pure form or in admixture with each other are intended to be embraced within the scope of the present invention.

Pure stereoisomeric forms of the compounds and intermediates as mentioned herein are defined as isomers substantially free of other enantiomeric or diastereomeric forms of the same basic molecular structure of said compounds or intermediates. In particular, the term 'stereoisomerically pure' concerns compounds or intermediates having a stereoisomeric excess of at least 80% (i. e. minimum 90% of one isomer and maximum 10% of the other possible isomers) up to a stereoisomeric excess of 100% (i.e. 100% of one isomer and none of the other), more in particular, compounds or intermediates having a stereoisomeric excess of 90% up to 100%, even more in particular having a stereoisomeric excess of 94% up to 100% and most in particular having a stereoisomeric excess of 97% up to 100%. The terms 'enantiomerically pure' and 'diastereomerically pure' should be understood in a similar way, but then having regard to the enantiomeric excess, respectively the diastereomeric excess of the mixture in question.

Pure stereoisomeric forms of the compounds and intermediates of this invention may be obtained by the application of art-known procedures. For instance, enantiomers may be separated from each other by the selective crystallization of their diastereomeric salts with optically active acids. Alternatively, enantiomers may be separated by chromatographic techniques using chiral stationary phases. Said pure stereochemically isomeric forms may also be derived from the corresponding pure stereochemically isomeric forms of the appropriate starting materials, provided that the reaction occurs stereospecifϊcally. Preferably, if a specific stereoisomer is desired, said compound will be synthesized by stereospecific methods of preparation. These methods will advantageously employ enantiomerically pure starting materials.

The diastereomeric racemates of formula (I) can be obtained separately by conventional methods. Appropriate physical separation methods which may advantageously be employed are, for example, selective crystallization and chromatography, e.g. column chromatography.

It is clear to a person skilled in the art that the compounds of formula (I) contain at least one asymmetric center and thus may exist as different stereoisomeric forms. This asymmetric center is indicated with a asterisk (*) in the figure below.

The absolute configuration of each asymmetric center that may be present in the compounds of formula (I) may be indicated by the stereochemical descriptors R and S, this R and S notation corresponding to the rules described in Pure Appl. Chem. 1976, 45, 11-30. The carbon atom marked with the asterisk •(*) preferably has the R configuration.

The present invention is also intended to include all isotopes of atoms occurring on the present compounds. Isotopes include those atoms having the same atomic number but . different mass numbers. By way of general example and without limitation, isotopes of hydrogen include tritium and deuterium. Isotopes of carbon include C-13 and C-14. Whenever used hereinafter, the term "compounds of formula (I)", or "the present compounds" or similar term is meant to include the compounds of general formula (I), their N-oxides, salts, stereoisomeric forms, racemic mixtures, prodrugs, esters and metabolites, as well as then quaternized nitrogen analogues.

A suitable group of compounds are those compounds according to formula (I) wherein :

R₉ , R_10a and R_10b are, each independently, hydrogen, Cm.alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(Cι_-4dkyl)aminocarbonyl,

C₃. cycloalkyl, C₂.₆alkenyl, C_2-6alkynyl or C_1- alkyl optionally substituted with aryl, Het¹, Het², C_3-7cycloalkyl, C_Malkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or d^C_Malky^aminocarbonyl, aminosulfonyl, C_1-4alkylS(O)t, hydroxy, cyano, halogen or amino optionally mono- or disubstituted where the substituents are selected from C_1- alkyl, aryl, arylC_1-4alkyl, C_3-7cycloalkyl, Het¹, Het², Het Ci^alkyl and Het Ci^alkyl; whereby R₉, Rιo_a and the carbon atoms to which they are attached may also form a C_3-7cycloalkyl radical; R_lla is hydrogen, C_2-6alkenyl, C_2-6alkynyl, C_3- cycloalkyl, aryl, aminocarbonyl optionally mono- or disubstituted, aminoC_1- alkylcarbonyloxy optionally mono- or disubstituted, C_1-4alkyloxycarbonyl, aryloxycarbonyl, Het y- carbonyl, Het²oxycarbonyl, aryloxycarbonylCi galkyl, arylC_1-4alkyloxy- carbonyl, Cι- alkylcarbonyl, C_3- cycloalkylcarbonyl, C₃. cycloalkyl- C_3- cycloalkylcarbonyloxy, carbonyloxy, Ci^alkylcarbonyloxy, arylC_Malkylcarbonyloxy, arylcarbonyloxy, aryloxycarbonyloxy, Het¹ carbonyl, He^carbonyloxy, Het²carbonyloxy, Het²C_1- alkylcarbonyloxy,

Het²C_1-4alkyloxycarbonyloxy or C_1-4alkyl optionally substituted with aryl, aryloxy, Het² or hydroxy; wherein the substituents on the amino groups are each independently selected from C_3-7cycloalkyl, C_3-7cycloarkylC_1- alkyl, Het¹, Het², Het^ alkyl and Het²C_1-4alkyl;

Ru_b is hydrogen, C_3-7cycloalkyl, C_2-6alkenyl, C_2-6alkynyl, aryl, Het¹, Het² or C_1-4alkyl optionally substituted with halogen, hydroxy, C_1-4alkylS(=O)_t, aryl, C_3- cycloalkyl, Het¹, Het², amino optionally mono- or disubstituted where the substituents are selected from Ci^alkyl, aryl, arylCi^alkyl, C_3-7cycloalkyl, Het¹, Het², and

He^C^alkyl; whereby Ru_b may be linked to the remainder of the molecule via a sulfonyl group; t is zero, 1 or 2; L is -C(=O)-, -O-C(=O)-, -NR₈-C(=O , -O-Cι.₆alkanediyl-C(==O)-,

-NR₈-C_1-6alkanediyl-C(=O)-, -S(=O)₂-, -O-S(=O)₂-, -NR₈-S(=O)₂ whereby either the C(=O) group or the S(=O)₂ group is attached to the R₂ moiety; R₄ is hydrogen, C^alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(Cι- alkyl)aminocarbonyl, C_3-7cycloalkyl, C_2-6alkenyl, C_2-6alkynyl, or Cι_-6alkyl optionally substituted with one or more substituents selected from aryl, Het¹, Het², C₃. cycloalkyl, C_1- alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(Ci-₄alkyl)aminocarbonyl, aminosulfonyl, C_MalkylS(=^:O)t, hydroxy, cyano, halogen and amino optionally mono- or disubstituted where the substituents are selected from C_1-4alkyl, aryl, arylC_1-4alkyl, C3_-7cycloalkyl, C_3- cycloalkyl-

C_1-4alkyl, Het¹, Het², He^C^alkyl and Het²Cι_-4alkyl; and R₆ is Cι-₆alkyloxy, Het¹, Het y, Het², Het²oxy, aryl, aryloxy or amino; and in case -A- is other than C_1-6alkanediyl then R₆ may also be C_1-6alkyl, Het^Malkyl, aryloxyCι- alkyl or aminoC_1-4alkyl; whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents selected from C_1-4alkyl, C₁. alkylcarbonyl, C_1-4alkyloxycarbonyl, aryl, arylcarbonyl, aryloxycarbonyl, Het¹, Het², arylC_1-4alkyl, Het^_Malkyl or Het^_Malkyl.

A particular group of compounds are those compounds of formula (I) wherein one or more of the following restrictions apply :

Ri is hydrogen, Het¹, Het², aryl, He^Ci-_δalk l, Het²C_1-6alkyl, arylCι_₆alkyl, more in particular, Ri is a saturated or partially unsaturated monocyclic or bicyclic heterocycle having 5 to 8 ring members, which contains one or more heteroatom ring members selected from nitrogen, oxygen or sulfur and which is optionally substituted, or phenyl optionally substituted with one or more substituents; R₂ is hydrogen; L is -C(=O)-, -O-C(=O)-, more in particular, L is

-O-C(=O)- or -O-C_1-6alkanediyl-C(=O)-, whereby in each case the C(=O) group is attached to the R₂ moiety;

R₃ is arylC_1-4alkyl, in particular, arylmethyl, more in particular phenylmethyl; R4 is optionally substiftited.Ci-βalkyl, in particular unsubstituted C_1-6alkyl or Cι_₆alkyl optionally substituted with one or more substituents selected from aryl, Het¹, Het , C3- cycloalkyl and amino optionally mono- or disubstituted where the substituents are selected from C_1-4alkyl, aryl, Het¹ and Het²;

A is Cι_₆alkanediyl, -C(=O)- or C_1-6alkanediyl-C(=O)-, in particular, A is 1,2-ethanediyl, 1,3-propanediyl or -C(=O)-; R₅ is hydrogen, Cι_-6alkyl, He^ -_όalkyl, aminoCι_-6alkyl whereby the amino group may optionally be mono- or di-substituted with in particular, R₅ is hydrogen or C_1-6alkyl; R₆ is Cι_-6alkyloxy, Het¹, aryl, amino; and in case -A- is other than Cι_-6alkanediyl then R₆ may also be Ci-βalkyl, whereby each of the amino groups may optionally be substituted; in particular, R₆ is Cj_-6alkyloxy, optionally substituted amino; and in case -A- is other than Cι_-6alkanediyl R₆ is Cι- alkyl; -A-R₆ is hydroxyC_1- alkyl; or R₅ and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het¹.

A special group of compounds are those compounds of formula (I) wherein Ri is Het¹, aryl, Het²d-₆aιkyl; R₂ is hydrogen; L is -C(=O)-, -O-C(=O)-, -O-CH₂-C(=O)-, whereby in each case the C(=O) group is attached to the NR₂ moiety; R₃ is phenyl- methyl; and R is C_1-6alkyl.

Also a special group of compounds are those compounds of formula (I) wherein A is Cι_-6alkanediyl or -C^O)-; R₅ is hydrogen or methyl; R₆ is C_1-6alkyloxy, Het¹, amino; and in case -A- is other than Cι_-6alkanediyl then R₆ may also be C_1-6alkyl, He^ . ₄alkyl or aminoC₁-₄alkyl; whereby each of the amino groups may optionally be substituted.

A suitable group of compounds are those compounds of formula (I) wherein A is d_ ₆alkanediyl or -C(=O)-; R₅ is hydrogen or methyl; R is Het²; and in case -A- is other than C_1-6alkanediyl then R₆ may also be He^Ci^alkyl; whereby each of the amino groups may be optionally substituted.

Yet another special group of compounds are those compounds of formula (I) wherein A is -C(=O)- and R₆ is C_1- alkyloxy or C_1-6alkyl.

Another group of compounds are those compounds of formula (I) wherein wherein A is -C(=O)- and R₆ is Het², Het¹ or optionally mono- or disubstituted aminoC_1-6alkyl.

An interesting group of compounds are those compounds of formula (I) wherein -A- is carbonyl and R₆ is aryl, whereby the amino groups may optionally be substituted; or -A- is carbonyl, R₆ is C_halky! and R₅ is He^ -ealkyl or aminoC_1-6alkyl whereby the amino group may optionally be mono- or di-substituted with . Another interesting group of compounds are those compounds of formula (I) wherein -

A- is Cι_-6alkanediyl and R₆ is amino and Het¹; whereby the amino group may optionally be mono- or di-substituted with C_hal y!.

Another interesting group of compounds are those compounds of formula (I) wherein

Ri hydrogen, C_1-6alkyl, C_2-6alkenyl, arylCι_₆alkyl, C3_-7cyclo alkyl, d^cycloalkyld. ealkyl, aryl, Het¹, Het², Het²C_1-6alkyl; wherein Het¹ in the definition of

Ri is a saturated or partially unsaturated monocyclic heterocycle having 5 or 6 ring members, which contains one or more heteroatom ring members selected from nitrogen, oxygen or sulfur and which is optionally substituted on one or more carbon atoms.

Another interesting group of compounds are those compounds of formula (I) wherein L is -O-C_1-6alkanediyl-C(=O)-.

Another interesting group of compounds are those compounds of formula (I) wherein A is Cι_-6alkanediyl, whereby the point of attachment to the nitrogen atom is the Cμgalkanediyl group in those moieties containing said group;

R₅ is hydrogen, Ci_₆alkyl, He^d-_δalkyl, Het²Cι_-6alkyl, aminoC_1-6alkyl whereby the amino group may optionally be mono- or di-substituted with C_1-4alkyl; and in case -A- is -C(=O)- then R⁶ is Ci-ealkyloxy, Het¹, Het¹ oxy or Het²oxy, aryl, aryloxyC_1-4alkyl or aminoC_Malkyl; and in case -A- is C_1-6alkanediyl then R₆ is amino, d_6alkyloxy, Het¹, Het¹ oxy or Het²oxy; and in case -A- is C_1-6alkanediyl-C(=O)- then R₆ is d-galkyloxy, Het¹, Het¹ oxy or Het²oxy, aryl, C_1-6alkyl, He^d^alkyl, Het^xyC^alkyl, Het²C_1-4alkyl, Het²oxyCι-4alkyl, aryloxyC_1-4alkyl or aminoC_1-4alkyl; whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents selected from aryl, arylcarbonyl, aryloxycarbonyl, Het¹, Het², aryl-

Ci^alkyl, He^C^alkyl or Het²C_walkyl; and R₅ and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het¹ whereby Het¹ is substituted by at least an oxo group.

A particular group of compounds are those compounds of formula (I) wherein one or more of the following restrictions apply : Ri is hydrogen, Het¹, Het², aryl, He^d^aU y!, Het²Cι_-6alkyl, arylCι.₆alkyl, more in particular, Ri is a saturated or partially unsaturated monocyclic or bicyclic heterocycle having 5 to 8 ring members, which contains one or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur and which is optionally substituted, or phenyl optionally substituted with one or more substituents; R₂ is hydrogen; L is -C(=O)-, -O-C(=O)-, -O-Cι_₆alkanediyl-C(=O)-, more in particular, L is

-O-C(=O)- or -O-C_1-6alkanediyl-C(=O)-, whereby in each case the C(=O) group is attached to the NR₂ moiety;

R₃ is arylC_1-4alkyl, in particular, arylmethyl, more in particular phenylmethyl; R₄ is optionally substituted C_1-6alkyl, in particular unsubstituted C_1-6alkyl or Cι_₆alkyl optionally substituted with one or more substituents each independently selected from aryl, Het¹, Het², C_3- cycloalkyl and amino optionally mono- or disubstituted where the substituents are each independently selected from Cι- alkyl, aryl, Het¹ and Het²; A is Cι_-6alkanediyl, -C(=O)- or Cι_-6alkanediyl-C(=O)-, in particular, A is

1,2-ethanediyl, 1,3-ρroρanediyl or -C(=O)-; R₅ is hydrogen, d-ealkyl, aminoCι_-6alkyl whereby the amino group may optionally be mono- or di-substituted with in particular, R₅ is hydrogen or Cι_-6alkyl; R₆ is Ci-δalkyloxy, Het¹, aryl, amino; and in case -A- is other than C_1-6alkanediyl then R₆ may also be Ci-βalkyl, He^d^alkyl, aryloxyC_1-4alkyl or aminoCi-βalkyl; whereby each of the amino groups may optionally be substituted; in particular, R₆ is Cι_-6alkyloxy, optionally substituted amino; and in case -A- is other than

Cι_-6alkanediyl R₆ is d_-6alkyl; -A-R₆ is hydroxyC_1-6alkyl; or R5 and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het

Another interesting group of compounds are those compounds of formula (I) wherein - A- is C_1-6alkanediyl and R₆ is amino or Het¹; whereby the amino group may optionally be mono- or di-substituted with Cι-₄alkyl.

Another interesting group of compounds are those compounds of formula (I) wherein A is Ci_₆alkanediyl, -C(=O)- or Cι_-6alkanediyl-C(=O)-; whereby the point of attachment to the nitrogen atom is the Cι-₆alkanediyl group in those moieties containing said group; R₅ is hydrogen, d_-6aιkyl, Het¹C₁.₆alkyl, Het²Cι_-6alkyl, aminoCι_-6alkyl whereby the amino group may optionally be mono- or di-substituted with Ci^alkyl; and in case -A- is -C(=O then R₆ is Cι_-6alkyloxy, Het¹, He^oxy or Het²oxy, aryl,

Het^i^ lkyl, Het yC_Malkyl, Het C_1-4alkyl, He^oxyC^alkyl, arylC_1-4alkyl, aryloxyd^alkyl or aminoC_1-4alkyl; and

I t 9 in case -A- is d-_δalkanediyl then Rg is amino, d^alkyloxy, Het , Het oxy or Het oxy; and in case -A- is C_1-6alkanediyl-C(=O)- then R₆ is C_1-6alkyloxy, Het¹, Het oxy or Het²oxy, aryl, C_1-6alkyl, Het^wal yl, Het^xyCwalkyl, Het²C_1-4alkyl, Het²oxyCι_-4alkyl, whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents each independently selected from Ci^alkyl, Ci alkyloxycarbonyl, aryl, arylcarbonyl, aryloxycarbonyl, Het¹, Het², arylC_Malkyl, He^C^alkyl or Het²C_1-4alkyl; and R₅ and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het¹ whereby Het¹ is substituted by at least an oxo group.

Another group of compounds are those of formula (I) wherein Ri is Het²C_1-6alkyl, L is -C(=O)-, -O-C(=O)-, -O-C_I-6alkanediyl-C(=O)- ; in particular the Het² moiety in the definition of Ri is an aromatic heterocycle having 5 or 6 ring members, which contain one or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur, more in particular the Het² moiety is an aromatic heterocycle having 5 or 6 ring members, which contain two or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur.

Suitably, the SO₂ moiety of the sulfonamide in the compounds of the present invention is para vis-a-vis the nitrogen of the benzoxazole moiety.

Another group of suitable compounds are those of formula (I) wherein A is Cι_₆alkane- diyl or -C(=O)-; R₅ is hydrogen or methyl; and R₆ is C_1-6alkyloxy, Het¹, Het², amino or amino Ci_₆alkyl; whereby each amino optionally may be mono- or disubstituted where the substituents are each independently selected from Ci^alkyl, aryl, arylC_1- alkyl, C₃-₇cycloalkyl, C₃-₇cycloalkyld galkyl, Het¹, Het², Het^ alkyl and He^Ci^alkyl.

Another group of suitable compounds are those of formula (I) wherein Ri is Het or

9 9

Het Cι_-6alkyl; wherein said Het in the definition of Ri is an aromatic heterocycle having at least one heteroatom each independently selected from nitrogen, oxygen and sulfur; L is -C(=O)-, -O-C(=O)- or -O-Cι_-6alkyl-C(=O)-; A is C_1-6alkanediyl or - C(=O)-; R₅ is hydrogen or methyl; and R₆ is Cι_-6alkyloxy, Het¹, Het², amino or aminoCi^alkyl; whereby each amino optionally may be mono- or disubstituted, where the substituents are each independently selected from C^aU yl, aryl, arylC_1-4alkyl, C_3-7cycloallcyl, C₃-₇cycloalkylC_Malkyl, Het¹, Het², He^Ci^alkyl and Het²Cι^alkyl.

Another group of suitable compounds are those of formula (I) wherein Ri is 2-thiazolylmethyl-; and L is -O-C(=O)~.

Another group of suitable compounds are those of formula (I) wherein R₅ is hydrogen; A is -C(=O)-; and R₆ is Het²; wherein said Het² contains 5 or 6 ring members and one heteroatom selected from nitrogen, oxygen or sulfur.

Another group of compounds are those of formula (I) wherein Ri is Het¹, having 8 ring members and two heteroatoms each independently selected from nitrogen, oxygen or sulfur; L is -O-C(=O)-; R₅ is hydrogen or methyl; A is -C(=O)-, Cι_-6alkanediyl; and R₆ is optionally mono- or disubstituted aminoC_Malkyl, Het¹ or Het²; wherein said Het^{2 •} contains 5. or 6 ring members and one heteratom selected from nitrogen, oxygen or sulfur; wherein the amino substituents are each independently selected from Ci^alkyl, aryl, arylC_1-4alkyl, C_3-7cycloalkyl, C_3-7cycloalkylCι_ alkyl, Het¹, Het², and Het²C_1-4alkyl.

The compounds of formula (I) can generally be prepared using procedures analogous to those procedures described in WO 95/06030, WO 96/22287, WO 96/28418,

WO 96/28463, WO 96/28464, WO 96/28465 and WO 97/18205.

Particular reaction procedures to make the present compounds are described below. In the preparations described below, the reaction products may be isolated from the medium and, if necessary, further purified according to methodologies generally known in the art such as, for example, extraction, crystallization, trituration and chromatography.

Scheme A

(a-6) (a-8)

The 2-acetamido-6-chlorosulfonylbenzoxazole (intermediate a-2) was prepared following the procedure described in EP-A-0,445,926.

Intermediates a-4 were prepared by reacting an intermediate a-3, prepared according to the procedure described in WO97/18205 and also depicted in scheme C, with an intermediate a-2 in a reaction-inert solvent such as dichloromethane, and in the presence of a base such as triethylamine and at low temperature, for example at 0 °C. The Boc group in the intermediate a-3 is a protective tert-butyloxycarbonyl group. It may conveniently be replaced by another suitable protective group such as phtalimido or benzyloxycarbonyl. Using intermediate a-4 as a starting material, intermediate a-5 was deprotected using an acid such as trifruoroacetic acid in a suitable solvent such as dichloromethane. The resulting intermediate may be f rther reacted with an intermediate of formula Rι-L-(leaving group) in the presence of a base such as triethylamine and optionally in the presence of l-(3-dimemylarmnopropyl)-3~e ylcarbodiimide hydrochloric acid (EDC) or an alcohol such as tert-butanol, and in a suitable solvent such as dichloromethane; thus forming intermediates a-6. Particularly, intermediates of formula Rι-C(=O)-OH are suitable to further react with an intermediate a-5.

Alternatively, intermediates a-4 may be deprotected with a strong acid such as hydrochloric acid in isopropanol, in a suitable solvent such as a mixture of ethanoi and dioxane, thus preparing an intermediate a-7. Intermediates a-8 can be prepared analogously to the procedure described for the preparation of intermediates a-6.

The procedure described in scheme A may also be used to prepare intermediates of formula a-6 wherein benzoxazole is substituted with a carbamate instead of an amide.

Scheme B

(b-9) (b-8)

Intermediate b-4 can be prepared according to the procedure described in scheme A. Intermediate b-5 can be prepared by for instance refluxing the 2(3H)-benzoxazolone derivative b-4 in the presence of a base such as, for example, sodiumhydroxide. Said intermediate b-5 can then be cyclized again using a reagent such as alkyl xanthic acid potassium salt (alkyl dithiocarbonate potassium salt) in a suitable solvent such as, for example, ethanoi at reflux temperature, thus preparing a 2(3H)-benzoxazolethione of formula b-6. Intermediate b-6 may then be derivatized with an amine of formula H₂N- A-R₆ in a suitable solvent such as acetonitrile to obtain an intermediate b-7. Debenzylation may be performed using art-known techniques such as the use of Pd on carbon in the presence of H₂ in a suitable solvent. The thus formed intermediate of formula b-8 may then be reacted with an intermediate of formula Rι-L-(leaving group) in the presence of a base such as triethylamine and optionally in the presence of EDC or an alcohol such as tert-butanol, and in a suitable solvent such as dichloromethane, thus obtaining an intermediate b-9.

A particular way of preparing acetamide substituted benzoxazoles is depicted in scheme C.

Scheme C

(o-3)

Intermediate c-1, prepared following the procedure as described in Scheme A, may be reacted with chloroacetylchloride, or a functional analogue, in the presence of a base such as triethylamine and in a solvent such as 1,4-dioxane in order to obtain an amide of formula c-2. Said intermediate c-2 can further be reacted with an amine of formula NR_aRb whereby R_a and Rb are defined as the possible substituents on an amino group in the variable R₆.

Another particular way of preparing acetamide substituted benzoxazoles is depicted in scheme D. Scheme D

Intermediate d-2 can be prepared by treating intermediate d-1, prepared following the procedure described in scheme A, with a base such as sodiumcarbonate in an aqueous medium such as a water dioxane mixture. The synthesis steps depicted in scheme D to obtain intermediate d-6 are all analogous to reaction procedures described in the above synthesis schemes.

A number of intermediates and starting materials used in the foregoing preparations are known compounds, while others may be prepared according to art-known methodologies of preparing said or similar compounds.

Scheme E

Intermediate e-2, corresponding to intermediate a-3 in scheme A, maybe prepared by adding an amine of formula H₂N-R₄ to an intermediate e-1 in a suitable solvent such as isopropanol.

A mixture of the 2-aminobenzoxazole f-1 in dichloromethane was stirred under an inert atmosphere such as nitrogen. R₆-COOH, EDC and HOBT (1 -hydroxy- 1-H- benzotriazole) were added. The mixture was stirred at room temperature for 48h. Water was added, the water layer was extracted with dichloromethane and the combined organic layers were washed with brine, dried under MgSO₄ and the solvent was evaporated under reduced pressure. Purification was performed on silica yielding f-2.

The compounds of formula (I) may also be converted to the corresponding N-oxide forms following art-known procedures for converting a trivalent nitrogen into its N-oxide form. Said N-oxidation reaction may generally be carried out by reacting the starting material of formula (I) with an appropriate organic or inorganic peroxide. Appropriate inorganic peroxides comprise, for example, hydrogen peroxide, alkali metal or earth alkaline metal peroxides, e.g. sodium peroxide, potassium peroxide; appropriate organic peroxides may comprise peroxy acids such as, for example, benzenecarboperoxoic acid or halo substituted benzenecarboperoxoic acid, e.g. 3-chlorobenzenecarboperoxoic acid, peroxoalkanoic acids, e.g. peroxoacetic acid, alkylhydroperoxides, e.g. tert-butyl hydroperoxide. Suitable solvents are, for example, water, lower alkanols, e.g. ethanoi and the like, hydrocarbons, e.g. toluene, ketones, e.g. 2-butanone, halogenated hydrocarbons, e.g. dichloromethane, and mixtures of such solvents.

An interesting group of intermediates are those intermediates of formula a-8, b-8 or c-1 wherein -A-Rβ is hydrogen. Said intermediates may also have pharmacological properties similar to those pharmacological properties of the compounds of formula (I). The present compounds can thus be used in animals, preferably in mammals, and in particular in humans as pharmaceuticals per se, in mixtures with one another or in the form of pharmaceutical preparations.

Furthermore, the present invention relates to pharmaceutical preparations which as active constituents contain an effective dose of at least one of the compounds of formula (I) in addition to customary pharmaceutically innocuous excipients and auxiliaries. The pharmaceutical preparations normally contain 0.1 to 90% by weight of a compound of formula (I). The pharmaceutical preparations can be prepared in a manner known per se to one of skill in the art. For this purpose, at least one of a compound of formula (I), together with one or more solid or liquid pharmaceutical excipients and/or auxiliaries and, if desired, in combination with other pharmaceutical active compounds, are brought into a suitable administration form or dosage form which can then be used as a pharmaceutical in human medicine or veterinary medicine.

Pharmaceuticals which contain a compound according to the invention can be administered orally, parenterally, e.g., intravenously, rectally, by inhalation, or topically, the preferred administration being dependent on the individual case, e.g., the particular course of the disorder to be treated. Oral administration is preferred.

The person skilled in the art is familiar on the basis of his expert knowledge with the auxiliaries which are suitable for the desired pharmaceutical formulation. Beside solvents, gel-forming agents, suppository bases, tablet auxiliaries and other active compound carriers, antioxidants, dispersants, emulsifiers, antifoams, flavor corrigents, preservatives, sofubilizers, agents for achieving a depot effect, buffer substances or colorants are also useful.

Due to their favorable pharmacological properties, particularly their activity against multi-drug resistant HIV protease enzymes, the compounds of the present invention are useful in the treatment of individuals infected by HIV and for the prophylaxis of these individuals. In general, the compounds of the present invention may be useful in the treatment of warm-blooded animals infected with viruses whose existence is mediated by, or depends upon, the protease enzyme. Conditions which may be prevented or treated with the compounds of the present invention, especially conditions associated with HIV and other pathogenic retroviruses, include AIDS, AIDS-related complex (ARC), progressive generalized lymphadenopathy (PGL), as well as chronic CNS diseases caused by retroviruses, such as, for example HIV mediated dementia and multiple sclerosis. The compounds of the present invention or any subgroup thereof may therefore be used as medicines against above-mentioned conditions. Said use as a medicine or method of treatment comprises the systemic administration to HIV-infected subjects of an amount effective to combat the conditions associated with HIV and other pathogenic retroviruses, especially HIN-1. Consequently, the compounds of the present invention can be used in the manufacture of a medicament useful for treating conditions associated with HIV and other pathogenic retroviruses, in particular medicaments useful for treating patients infected with multi-drug resistant HIV virus.

In a preferred embodiment, the invention relates to the use of a compound of formula (I) or any subgroup thereof in the manufacture of a medicament for treating or combating infection or disease associated with multi-drug resistant refrovirus infection in a mammal, in particular HIV-1 infection. Thus, the invention also relates to a method of treating a retroviral infection, or a disease associated with multi-drug resistant refrovirus infection comprising administering to a mammal in need thereof an effective amount of a compound of formula (I) or a subgroup thereof.

In another preferred embodiment, the present invention relates to the use of formula (I) or any subgroup thereof in the manufacture of a medicament for inhibiting a protease of a multi-drug resistant refrovirus in a mammal infected with said refrovirus, in particular HIV-1 refrovirus.

In another preferred embodiment, the present invention relates to the use of formula (I) or any subgroup thereof in the manufacture of a medicament for inhibiting multi-drag resistant retroviral replication, in particular HIV-1 replication.

The compounds of the present invention may also find use in inhibiting ex vivo samples containing HIV or expected to be exposed to HIV. Hence, the present compounds may be used to inhibit HIV present in a body fluid sample which contains or is suspected to contain or be exposed to HIV.

Also, the combination of an antiretroviral compound and a compound of the present invention can be used as a medicine. Thus, the present invention also relates to a product containing (a) a compound of the present invention, and (b) another antiretroviral compound, as a combined preparation for simultaneous, separate or sequential use in treatment of retroviral infections, in particular, in the treatment of infections with multi-drug resistant retroviruses. Thus, to combat or treat HIV infections, or the infection and disease associated with HIV infections, such as Acquired Immunodeficiency Syndrome (AIDS) or ADDS Related Complex (ARC), the compounds of this invention may be co-administered in combination with for instance, binding inhibitors, such as, for example, dextran sulfate, suramine, polyanions, soluble CD4; fusion inhibitors, such as, for example, T20, T1249, SHC-C; co-receptor binding inhibitors, such as, for example, AMD 3100 (Bicyclams), TAK 779; RT inhibitors, such as, for example, foscarnet and prodrugs; nucleoside RTIs, such as, for example, AZT, 3TC, DDC, DDI, D4T, Abacavir, FTC, DAPD, dOTC; nucleotide RTIs, such as, for example, PMEA, PMPA (tenofovir); NNRTIs, such as, for example, nevirapine, delavirdine, efavire z, 8 and 9-C1 TTBO (tivirapine), loviride, TMC-125, TMC-120, MKC-442, UC 781, UC 782, Capravirine, DPC 961, DPC963, DPC082, DPC083, calanolide A, SJ-3366, TSAO, 4"-deaminated TSAO; RNAse H inhibitors, such as, for example, SP1093V, PD126338; TAT inhibitors, such as, for example, RO-5-3335, K12, K37; integrase inhibitors, such as, for example, L 708906, L 731988; protease inhibitors, such as, for example, amprenavir, ritonavir, nelfinavir, saquinavir, indinavir, lopinavir, palinavir, BMS 186316, BMS 232632, DPC 681, DPC 684, tipranavir, AG1776, DMP 450, GS3333, KNI-413, KNI-272, L754394, L756425, LG-71350,

PD161374, PD173606, PD177298, PD178390, PD178392, PNU 140135, maslinic acid, U-l 40690; glycosylation inhibitors, such as, for example, castanospermine, deoxynojirimycine.

The combination may in some cases provide a synergistic effect, whereby viral infectivity and its associated symptoms may be prevented, substantially reduced, or eliminated completely.

The compounds of the present invention may also be administered in combination with immunomodulators (e.g., bropirimine, anti-human alpha interferon antibody, IL-2, methionine enkephalin, interferon alpha, and naltrexone) with antibiotics (e.g., pentamidine isothiorate) cytokines (e.g. Th2), modulators of cytokines, chemokines

(e.g. CCR5) or hormones (e.g. growth hormone) to ameliorate, combat, or eliminate

HIV infection and its symptoms.

The compounds of the present invention may also be administered in combination with modulators of the metabolization following application of the drug to an individual.

These modulators, include compounds that interfere with the metabolization at cytochromes, such as cytochrome P450. It is known that several isoenzymes exist of cytochrome P450, one of which is cytochrome P450 3A4. Ritonavir is an example of a modulator of metabolization via cytochrome P450.

For an oral administration form, compounds of the present invention are mixed with suitable additives, such as excipients, stabilizers or inert diluents, and brought by means of the customary methods into the suitable administration forms, such as tablets, coated tablets, hard capsules, aqueous, alcoholic, or oily solutions. Examples of suitable inert carriers are gum arabic, magnesia, magnesium carbonate, potassium phosphate, lactose, glucose, or starch, in particular, corn starch. In this case the preparation can be carried out both as dry and as moist granules. Suitable oily excipients or solvents are vegetable or animal oils, such as sunflower oil or cod liver oil. Suitable solvents for aqueous or alcoholic solutions are water, ethanoi, sugar solutions, or mixtures thereof. Polyethylene glycols and polypropylene glycols are also useful as further auxiliaries for other administration forms.

For subcutaneous or intravenous administration, the active compounds, if desired with the substances customary therefor such as solubilizers, emulsifiers or further auxiliaries, are brought into solution, suspension, or emulsion. The compounds of formula (I) can also be lyophilized and the lyophilizates obtained used, for example, for the production of injection or infusion preparations. Suitable solvents are, for example, water, physiological saline solution or alcohols, e.g. ethanoi, propanol, glycerol, in addition also sugar solutions such as glucose or mannitol solutions, or alternatively mixtures of the various solvents mentioned.

Suitable pharmaceutical formulations for administration in the form of aerosols or sprays are, for example, solutions, suspensions or emulsions of the compounds of formula (I) or their physiologically tolerable salts in a pharmaceutically acceptable solvent, such as ethanoi or water, or a mixture of such solvents. If required, the formulation can also additionally contain other pharmaceutical auxiliaries such as surfactants, emulsifiers and stabilizers as well as a propellant. Such a preparation customarily contains the active compound in a concentration from approximately 0.1 to 50%, in particular from approximately 0.3 to 3% by weight.

In order to enhance the solubility and/or the stability of the compounds of formula (I) in pharmaceutical compositions, it can be advantageous to employ α-, β- or γ-cyclo- dextrins or their derivatives. Also co-solvents such as alcohols may improve the solubility and/or the stability of the compounds of formula (I) in pharmaceutical compositions. In the preparation of aqueous compositions, addition salts of the subject compounds are obviously more suitable due to their increased water solubility.

Appropriate cyclodextrins are α-, β- or γ-cyclodextrins (CDs) or ethers and mixed ethers thereof wherein one or more of the hydroxy groups of the anhydroglucose units of the cyclodextrin are substituted with C_1-6alkyl, particularly methyl, ethyl or isopropyl, e.g. randomly methylated β-CD; hydroxyCι_-6alkyl, particularly hydroxy- ethyl, hydroxypropyl or hydroxybutyl; carboxyCι.₆alkyl, particularly carboxymethyl or carboxyethyl; d-₆alkyl-carbonyl, particularly acetyl; or carboxyCι_-6alkyloxyCι_-6alkyl, particularly carboxymethoxypropyl or carboxyethoxy- propyl; Ci-ealkylcarbonyloxyCi-ealkyl, particularly 2-acetyloxypropyl. Especially noteworthy as complexants. and/or solubihzers are β-CD, randomly methylated β-CD, 2,6-dirnethyl-β-CD, 2-hydroxyethyl-β-CD, 2-hydroxyethyl-γ-CD, 2-hydroxy- propyl-γ-CD and (2-carboxymethoxy)propyl-β-CD, and in particular 2-hydroxy- propyl-β-CD (2-HP-β-CD).

The term mixed ether denotes cyclodextrin derivatives wherein at least two cyclodextrin hydroxy groups are etherified with different groups such as, for example, hydroxy-propyl and hydroxyethyl.

An interesting way of formulating the present compounds in combination with a cyclodextrin or a derivative thereof has been described in EP-A-721,331. Although the formulations described therein are with antifungal active ingredients, they are equally interesting for formulating the compounds of the present invention. The formulations described therein are particularly suitable for oral administration and comprise an antifungal as active ingredient, a sufficient amount of a cyclodextrin or a derivative thereof as a solubilizer, an aqueous acidic medium as bulk liquid carrier and an alcoholic co-solvent that greatly simplifies the preparation of the composition. Said formulations may also be rendered more palatable by adding pharmaceutically acceptable sweeteners and/or flavors.

Other convenient ways to enhance the solubility of the compounds of the present invention in pharmaceutical compositions are described in WO 94/05263, WO 98/42318, EP-A-499,299 and WO 97/44014, all incorporated herein by reference.

More in particular, the present compounds may be formulated in a pharmaceutical composition comprising a therapeutically effective amount of particles consisting of a solid dispersion comprising (a) a compound of formula (I), and (b) one or more pharmaceutically acceptable water-soluble polymers.

The term "a solid dispersion" defines a system in a solid state (as opposed to a liquid or gaseous state) comprising at least two components, wherein one component is dispersed more or less evenly throughout the other component or components. When said dispersion of the components is such that the system is chemically and physically uniform or homogenous throughout or consists of one phase as defined in thermodynamics, such a solid dispersion is referred to as "a solid solution". Solid solutions are preferred physical systems because the components therein are usually readily bioavailable to the organisms to which they are administered.

The term "a solid dispersion" also comprises dispersions which are less homogenous throughout than solid solutions. Such dispersions are not chemically and physically uniform throughout or comprise more than one phase.

The water-soluble polymer in the particles is conveniently a polymer that has an apparent viscosity of 1 to 100 mPa.s when dissolved in a 2 % aqueous solution at 20°C solution.

Preferred water-soluble polymers are hydroxypropyl methylcelluloses or HPMC. HPMC having a methoxy degree of substitution from about 0.8 to about 2.5 and a hydroxypropyl molar substitution from about 0.05 to about 3.0 are generally water soluble. Methoxy degree of substitution refers to the average number of methyl ether groups present per anhydroglucose unit of the cellulose molecule. Hydroxy-propyl molar substitution refers to the average number of moles of propylene oxide which have reacted with each anhydroglucose unit of the cellulose molecule.

The particles as defined hereinabove can be prepared by first preparing a solid dispersion of the components, and then optionally grinding or milling that dispersion. Various techniques exist for preparing solid dispersions including melt-extrusion, spray-drying and solution-evaporation, melt-extrusion being preferred.

It may further be convenient to formulate the present compounds in the form of nanoparticles which have a surface modifier adsorbed on the surface thereof in an amount sufficient to maintain an effective average particle size of less than 1000 nm. Useful surface modifiers are believed to include those which physically adhere to the surface of the antiretroviral agent but do not chemically bond to the antiretroviral agent.

Suitable surface modifiers can preferably be selected from known organic and inorganic pharmaceutical excipients. Such excipients include various polymers, low molecular weight oligomers, natural products and surfactants. Preferred surface modifiers include nonionic and anionic surfactants.

Yet another interesting way of formulating the present compounds involves a pharmaceutical composition whereby the present compounds are incorporated in hydrophilic polymers and applying this mixture as a coat film over many small beads, thus yielding a composition with good bioavailability which can conveniently be manufactured and which is suitable for preparing pharmaceutical dosage forms for oral administration.

Said beads comprise (a) a central, rounded or spherical core, (b) a coating film of a hydrophilic polymer and an antiretroviral agent and (c) a seal-coating polymer layer.

Materials suitable for use as cores in the beads are manifold, provided that said materials are pharmaceutically acceptable and have appropriate dimensions and firmness. Examples of such materials are polymers, inorganic substances, organic substances, and saccharides and derivatives thereof.

Another aspect of the present invention concerns a kit or container comprising a compound of formula (I) in an amount effective for use as a standard or reagent in a test or assay for determining the ability of a potential pharmaceutical to inhibit HIV protease, HIV growth, or both. This aspect of the invention may find its use in pharmaceutical research programs.

The compounds of the present invention can be used in phenotypic resistance monitoring assays, such as known recombinant assays, in the clinical management of resistance developing diseases such as HIV. A particularly useful resistance monitoring system is a recombinant assay known as the Antivirogram™. The Antivirogram™ is a highly automated, high throughput, second generation, recombinant assay that can measure susceptibility, especially viral susceptibility, to the compounds of the present invention. (Hertogs K, de Bethune MP, Miller V et al. Antimicrob Agents Chemother, 1998; 42(2):269-276, incorporated by reference).

The compounds of the present invention may also be linked to maleimide or derivatives thereof to form conjugates.

The dose of the present compounds or of the physiologically tolerable salt(s) thereof to be administered depends on the individual case and, as customary, is to be adapted to the conditions of the individual case for an optimum effect. Thus it depends, of course, on the frequency of administration and on the potency and duration of action of the compounds employed in each case for therapy or prophylaxis, but also on the nature and severity of the infection and symptoms, and on the sex, age, weight and individual responsiveness of the human or animal to be treated and on whether the therapy is acute or prophylactic. Customarily, the daily dose of a compound of formula (I) in the case of administration to a patient approximately 75 kg in weight is 1 mg to 3g, suitably 1 mg o lg, preferably 3 mg to 0.5 g, more preferably 5 mg to 300 mg. The dose can be adrninistered in the form of an individual dose, or divided into several, e.g. two, three, or four, individual doses.

Experimental Part

Preparation of the compounds of formula β) and their intermediates

Example 1 : Preparation of compound 1 a) A mixture of 5g 2-acetamidobenzoxazole and 20 ml chlorosulfonic acid in dichloromethane was heated to 60°C for 2 hours (h). After cooling the mixture was poured into ice. The organic layer was separated and dried over MgSO₄, thus yielding 2-acetamido-6-chlorosulfonylbenzoxazole (interm. 1) ^* b) A mixture of 3.4 g of [(lS,2R)-2-hydroxy-3-[(2-methylpropyl)amino]-l-(phenyl- methyl)propyl] carbamic acid 1,1-dimethylethyl ester, prepared analogously to the procedure described in WO 97/18205, and 2.6 g of triethylamine in 100 ml of dichloro- methane was stirred at 0°C. Then 2.8 g of 2-acetamido-6-chlorosulfonylbenzoxazole was added and the reaction mixture stirred overnight at room temperature. After washing with water, the organic layer was separated, dried and evaporated. The brown solid obtained was reslurried in warm diisopropyl ether, cooled and

filtered off, thus yielding 88% (5.1 g) of interm. 2 :

c) To a mixture of 1.2 g of intermediate 2 in 25 ml of dichloromethane, 2.3 ml of trifluoracetic acid were added. The reaction mixture as stirred at room temperature for 6 hours. Extra dichloromethane was added and washed withNaHCO₃ solution. The organic layer was dried and evaporated under reduced pressure, yielding 970 mg (99%)

of intermediate 3:

d) To a mixture of 1.1 g intermediate 3 and 364 mg triethylamine in dichloromethane was added 685 mg l-[[[[(3R,3aS,6aR)-hexahydrofvu-o[2,3-b]furan-3-yl]oxy]carbonyl]- oxy]- 2,5-pyrrolidinedione (described in W09967417). This mixture is stirred at room temperature for 12 hours. After evaporation of dichloromethane under reduced pressure, the crude product is purified on silica. Thus, 900 mg of compound 1 was obtained with a yield of 59%. Example 2 : Preparation of compound 5 a) A mixture of 1 g of [(lS,2R)-2-hydroxy-3-[(2-me ylρroρyl)anτino]-l-(ρhenyl- methyl)propyl]carbamic acid 1 , 1-dimethylethyl ester and 901 mg of triethylamine in ^'• 40 ml of dichloromethane was stirred at 0°C. Then 1 g of 2-(Ethoxycarbamoyl)-6- chlorosulfonylbenzoxazole was added and the reaction mixture stirred overnight at room temperature. After washing with sat NaHCO₃, the organic layer was separated, dried and evaporated, yielding 1.7 g (94%) of intermediate 4

BocNtT NS0₂

°^H / I _/Jj>— N— C— O— CH₂-CH₃

b) To a mixture of 1.7 g of intermediate 4 in 25 ml of dichloromethane, 3.2 g of trifluoracetic acid were added. The reaction mixture as stirred at room temperature for 6 hours. Extra dichloromethane was added and washed with NaHCO₃ solution. The organic layer was dried and evaporated under reduced pressure yielding 1.4 g (99%) of

intermediate 5

c) A mixture of 380 mg of intermediate 5, 107 mg of 1 -hydroxybenzotriazole, 154 mg of l-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloric acid and 143 mg of 2-(2,6-dimethylphenoxy)acetic acid in 20 ml of dichloromethane, was stirred overnight at room temperature. The reaction mixture was then washed with 5% HC1, saturated • NaHCO₃ solution and brine. The organic layer was separated, dried and evaporated. The residue was purified by preparative-HPLC, yielding 141 mg (28%) of compound 5.

Example 3 : Preparation of compound 3

To a mixture of 1.2g intermediate 5 and 364 mg triethylamine in dichloromethane was added 685 mg l-[[[[(3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-yl]oxy]carbonyl]oxy]- 2,5-ρyrrolidinedione (described in W09967417). This mixture is stirred at room temperature for 12 hours. After evaporation of dichloromethane under reduced pressure, the crude product is purified on silica, thus yielding 1.1 g (70%) of compound 3.

Example 4 : Preparation of compound 2 a) To a mixture of 8 g β-[bis(phenylmemyl)ammo]- -[[(2-methylpropyl)amino]- methyl]-, (αR,βS)-benzenepropanol, prepared following the procedure in WO95/14653, and 3.2 g triethylamine in 150 ml dichloromethane was added at 0°C 3.9 g 6-chlorosulfonyl-benzoxazolone (prepared as described in EP 0403947). After stirring for 24 hours at room temperature the reaction mixture was washed with sat. NaHCO₃, 8 g of

intermediate 6

b) A mixture of 5.2 g intermediate 6 in 60 ml 10% NaOH-solution was heated to reflux overnight. After cooling the reaction mixture was acidified to pH=8 with 15% HC1. The aqueous phase was extracted two times with ethylacetate, yielding 3 g of

intermediate ? :

c) To a solution of 1.5 g intermediate 7 in ethanoi was added 361mg ethylpotassium xanthate. After refluxing this mixture for 16 hours, ethanoi was removed under vacuum. To the residue was added H O. After acidification to pH=6 the precipitate was filtered of, yielding, after drying,

1.4 g of intermediate 8

d) A mixture of 500 mg intermediate 8 and 70 mg NN-dimethylethylenediamine in -xylene was heated to 110°C for 3 hours. After evaporation of the solvent and purification with column chromatography 181 mg of intermediate 9 was obtained :

e) Debenzylation was performed with Pd/C and H₂ to afford intermediate 10. f) To a mixture of 95 mg intermediate 10 and 27 mg triethylamine in dichloromethane was added 51 mg l-[[[[(3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-yl]oxy]carbonyl]- oxy]-2,5-ρyrrolidinedione (described in W09967417). This mixture is stirred at room temperature for 12 hours. After evaporation of dichloromethane under reduced pressure, the crude product is purified on silica, yielding 83 mg of compound 2 (70%).

In an analogous way, compounds 4, 6, 7 and 8 were prepared.

Example 5: Synthesis of compound 10

0.23g of isonicotinic acid, 0.36g of EDC and 12mg of HOBT were mixed and added to lg of the 2-aminobenzoxazole intermediate 11 in 40ml of dichloromethane. The mixture was stirred under an inert atmosphere of nitrogen at room temperature for 48h. 50ml of water was added the water layer was extracted with dichloromethane and the combined organic layers were washed with brine, dried under MgSO and the solvent was evaporated under reduced pressure. Purification was performed on silica yielding 0.57g (48%) of compound 10. Example 6

6-1 6-2 6-3

A mixture of 2.5g 2-aminophenol (6-1) and 20 ml ethyl acetate was heated to 45°C. 3 g of cyanogen bromide was added to the mixture. The mixture was stirred at 45-50°C for 12 hours. After cooling to room temperature, 1.5g of sodium hydroxide in 15ml of water was added. The organic layer was separated and washed with brine until neutral pH. Toluene (5 ml) was added and the solvent was removed to yield 2.71 g (88%) 2-aminobenzoxazol (6-2). 7.5ml of chlorosulfonic acid was stirred at room temperature under an inert atmosphere. 5g of 2-aminobenzoxazol (6-2) was added in small portions. The temperature was kept between 30-60°C during the addition of 6-2. The mixture was heated to 80°C for 2 hours. 5.3 g of thionyl chloride was added drop wise, keeping the temperature at 65°C. The mixture was stirred during 2 hours. After cooling to 0°C 10ml of ethyl acetate and 10ml of a solution of sodium carbonate (IN) were added. The organic layer was separated from the water layer and this latter was extracted with ethyl acetate. The combined organic layers were dried over calcium chloride, yielding 7.8g (90%) of 2-amino-6-chlorosulfonylbenzoxazole (6-3).

Example 7

7-5

7-4

A mixture of lg of sodium methoxide and 10 ml of toluene was stirred at 0°C under nitrogen atmosphere . A mixture of 1.9g of methyl chloracetate (7-1) and l.lg of methylformate was added drop wise keeping the temperature between 5-10°C. The mixture was stirred for 2 hours at 0°C. After washing with water, the organic layer was dried and evaporated under reduced pressure yielding 2-chloro-3-oxo-propionic acid methyl ester (7-2).

A mixture of 2.4g of 2-chloro-3-oxo-propionic acid methyl ester (7-2), water 20ml and 1.75g of thiourea was refluxed for 2hours. The mixture was cooled to room temperature and 0.25g of norit was added and filtered. A solution of 2.5N sodium hydroxide was added to the filtrate until neutral pH. The filtration yielded 1.23g (44%) of 2- aminothiazole-5-carboxylic acid methyl ester (7-3).

The mixture of 2.15g of isoamyl nitrite and 10ml of dioxane was stirred at 80°C under a nitrogen atmosphere. A .solution of 1.23 g of 2-aminothiazole-5-carboxylic acid methyl ester (7-3) in 20ml of dioxane was added drop wise. The mixture was refluxed for 2 hours. After cooling to room temperature 30ml of ethyl acetate was added. The mixture was washed with brine and dried and the solvent evaporated under reduced pressure. The crude product is purified on silica, thus yielding 0.54g (48%) of thiazol 5 -carboxylic acid methyl ester (7-4). A mixture of 0.54 g of thiazol 5-carboxylic acid methyl ester (g-4) and 1 Oml tetrahydrofurane (THF) was stirred at 0°C under a nitrogen atmosphere. The mixture of 0.16g of lithium aluminium hydride and 5ml of ether was added drop wise. After lhour at 0°C water and 20% sodium hydroxide were added, and stirred during 30minutes (min). The mixture was filtered over decalite and the solvent was removed by azeofropique distillation with toluene yielding 0.3 g (69%) of thiazol-5-yl-methanol (7- 5).

Example 8

A mixture of 1. log of thiazol-5-yl-methanol (8-1) and 1.2g triethylamine (TEA) in

25ml of dichloromethane (DCM) was stirred at room temperature under an atmosphere of nitrogen. 2.56g of N,N'-disuccinimidyl carbonate was then added and the resulting mixture was stirred for 10-15 minutes. The solution was stirred for an additional 2 hours. The resulting intermediate (8-2) was used directly in the subsequent reaction with the amine (8-3). Instead of amines also salts thereof can be used.

Triethylamine 2g and the amine 5g (8-3) were added to dichloromethane 40ml and the resulting mixture was stirred at room temperature. Subsequently, a portion of the solution comprising 8-2 was added drop wise. The reaction mixture was stirred at room temperature for 2 hours. The reaction mixture was washed with water and then dried to yield compound (8-4).

8-4

Table 1

Compounds of the present invention prepared according to the methods described above. If no stereochemistry is indicated, the compound is present as a racemic mixture.

Antiviral analyses:

The compounds of the present invention were examined for anti- viral activity in a cellular assay. The assay demonstrated that these compounds exhibited potent anti- HIV activity against a wild type laboratory HIV strain (HIV-1 strain LAI). The cellular assay was performed according to the following procedure. Cellular Assay Experimental Method:

HIV- or mock-infected MT4 cells were incubated for five days in the presence of various concentrations of the inhibitor. At the end of the incubation period, all HIV- infected cells have been killed by the replicating virus in the control cultures in the absence of any inhibitor. Cell viability is measured by measuring the concentration of MTT, a yellow, water soluble tetrazolium dye that is converted to a purple, water insoluble formazan in the mitochondria of living cells only. Upon solubilization of the resulting formazan crystals with isopropanol, the absorbance of the solution is monitored at 540nm. The values correlate directly to the number of living cells remaining in the culture at the completion of the five day incubation. The inhibitory activity of the compound was monitored on the virus-infected cells and was expressed as EC₅₀ and EC₉₀. These values represent the amount of the compound required to protect 50% and 90%, respectively, of the cells from the cytopathogenic effect of the virus. The toxicity of the compound was measured on the mock-infected cells and was expressed as CC₅o, which represents the concenfration of compound required to inhibit the growth of the cells by 50%. The selectivity index (SI) (ratio CC₅o/EC₅₀) is an indication of the selectivity of the anti-HIV activity of the inhibitor. Wherever results are reported as e.g. pEdø or pCC₅o values, the result is expressed as the negative logarithm of the result expressed as EC5₀ or CC₅₀ respectively.

Antiviral spectrum:

Because of the increasing emergence of drug resistant HIV strains, the present compounds were tested for their potency against clinically isolated HIV strains harboring several mutations (Table 2 and 3). These mutations are associated with resistance to protease inhibitors and result in viruses that show various degrees of phenotypic cross-resistance to the currently commercially available drugs such as for instance saquinavir, ritonavir, nelfinavir, indinavir and amprenavir.

Table 2 List of mutations present in the protease gene of the HIV strains (A to F) used .

Results:

As a measure of the broad spectrum activity of the present compounds, the fold resistance (FR), defined as FR = ECso(mutant strain)/EC₅₀(HrV-l strain LAI), was determined. Table 3 shows the results of the antiviral testing in terms of fold resistance. As can be seen in this table, the present compounds are effective in inhibiting a broad range of mutant strains: Column A FR value towards mutant A, Column B: FR towards mutant B , Column C: FR towards mutant C, Column D: FR towards mutant D, Column E: FR towards mutant E, Column F: FR towards mutant F. The toxicity is expressed as the pCC₅₀ value as determined with mock fransfected cells.

Table 3. Results of the toxicity testing and the resistance testing against strain A to F (expressed as FR). ND indicates not determined

Biovailability:

Caco-2 permeability assay for intestinal absorption

The permeability of different compounds is evaluated according to a Caco-2 test protocol as described by Augustijns et al. (Augustijns et al. (1998). Int. J. ofPharm, 166, 45-54) whereby, Caco-2 cells at cell passage number between 32 and 45 are grown in 24-well transwell cell culture plates for 21 to 25 days. The integrity of the cell monolayer is checked by measuring the transepithelial electrical resistance (TEER). The test is performed at pH 7.4 and at 100 μM donor compound concentration.

Aqueous solubility at different pH levels

The equilibrium solubility in simulated gastrointestinal solutions under thermodynamic conditions is a good measure for the solubility profile of the compound in the stomach and the different parts of the intestine. Simulated gastric fluid (SGF) (without pepsin) is set at pH of 1.5. Simulated intestinal fluids (SIF) (without bile salts) are set at pH 5, pH 6.5, pH 7 and pH 7.5. The experimental protocol uses 96-weϊl flat-bottom microplates in which 1 mg of compound is added per well (stock solution in methanol) and evaporated to dryness. The compounds are resolubilized in SGF and SIF and incubated overnight on a horizontal shaking device at 37°C. After filtration, the compound concentrations are determined by UV-spectrophotometry.

Oral availability in the rat

The compounds are formulated as a 20 mg/ml solution or suspension in DMSO, PEG400 or cyclodextin 40% in water. For most experiments in the rat (male and female rats), three dosing groups are formed: 1/ single intraperitoneal (IP) dose at 20 mg kg using the DMSO formulation; 2/ single oral dose at 20 mg/kg using the PEG400 formulation and 3/ single oral dose at 20 mg/kg using the cyclodextrin formulation. Blood is sampled at regular time intervals after dosing and drug concentrations in the serum are determined using a LC-MS bioanalytical method. Serum concentrations are expressed in ng/mg after normalization to 10 mg/kg. Serum concentration at 30 minutes (30') and at 3 hours (180') can be determined as these values reflect the extent of absorption (30') and the speed of elimination (180'). The rat serum concentration at 30 min and 180 min following IP administration of 20 mg/kg of compound 4 are 1098 ng/ml and 553 ng/ml respectively.

Boosting the systemic bioavailability

With the described type of compounds (protease-inhibitors), it is known that inhibition of the metabolic degradation processes can markedly increase the systemic availability by reducing the first-pass metabolism in the liver and the metabolic clearance from the plasma. This 'boosting' principle can be applied in a clinical setting to the pharmacological action of the drag. This principle can be also explored both in the rat or the dog by simultaneous administration of a compound that inhibits the Cyt-p45O metabolic enzymes. Known blockers are for example ritonavir and ketoconazole.

Dosing a single oral dose of ritonvir at 5 mg kg in the rat and the dog may result in an increase of the systemic availability.

Protein Binding analyses: Human serum proteins like albumin (HSA) or α-1 acid glycoprotein (AAG) are known to bind many drugs, resulting in a possible decrease in the effectiveness of those compounds. In order to determine whether the present compounds would be adversely affected by this binding, the anti-HIV activity of the compounds was measured in the presence of human serum, thus evaluating the effect of the binding of the protease inhibitors to those proteins.

MT4 cells are infected with HIV-1 LAI at a multiplicity of infection (MOI) of 0.001- 0.01 CCID50 (50% cell culture infective dose per cell, CCID₅o). After 1 h incubation, cells are washed and plated into a 96 well plate containing serial dilutions of the compound in the presence of 10% FCS (foetal calf serum), 10% FCS + 1 mg/ml AAG (oci-acid glycoprotein), 1 % FCS + 45 mg/ml HSA (human serum albumin) or 50% human serum (HS). After 5 or 6 days incubation, the EC₅₀ (50% effective concentration in cell-based assays) is calculated by deterrnining the cell viability or by quantifying the level of HIN replication. Cell viability is measured using the assay described above. Into a 96 well plate containing serial dilutions of the compound in the presence of 10% FCS or 10% FCS + 1 mg/ml AAG, HIN (wild type or resistant strain) and MT4 cells are added to a final concentration of 200-250 CCID₅o/well and 30,000 cells/well, respectively. After 5 days of incubation (37°C, 5% CO₂), the viability of the cells is determined by the tefrazolium colorimetric MTT (3-[4,5-Dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide) method (Pauwels et al. J Virol. Methods 1988, 20, 309- 321).

Table 4 Effect of the protein binding on the in vitro activity of compound 1

Claims (28)

CLATMS

1. A compound having the formula

an N-oxide, salt, stereoisomeric form, racemic mixture, prodrug, ester or metabolite thereof, wherein

Ri and R₈ are, each independently, hydrogen, d.₆alkyl, C_2-6alkenyl, arylCι_-6alkyL

C_3-7cycloalkyl, C_3- cycloalkylCi-₆alkyl, aryl, Het¹, He^d^alkyl, Het²,

Het²C_1-6alkyl; Ri may also be a radical of formula

wherein

R₉ , R_10a and R_10b are, each independently, hydrogen, d^alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(C_1-4alkyl)aminocarbonyl, C_3- cycloalkyl, C_2-6alkenyl, C_2-6alkynyl or Cι_-4alkyl optionally substituted with aryl, Het carboxyl, aminocarbonyl, mono- or di(C_1-4alkyl)aminocarbonyl, amino sulfonyl, C_1-4alkylS(O)_t, hydroxy, cyano, halogen or amino optionally mono- or disubstituted where the substituents are each independently selected from C_1-4alkyl, aryl, arylC_1-4alkyl, C_3-7cycloalkyl, C_3- cycloalkylC_1-4alkyl, Het¹, Het², He^d^alkyl and Het²C_1-4alkyl; whereby R , Rio_a and the carbon atoms to which they are attached may also form a C_3- cycloalkyl radical; R₉ may also be oxo; R_lla is hydrogen, C_2-6alkenyl, C_2-6alkynyl, C_3-7cycloalkyl, aryl, aminocarbonyl optionally mono- or disubstituted, optionally mono- or disubstituted, aryloxycarbonyl, Het¹ oxy- carbonyl, Het oxycarbonyl, aryloxycarbonylC_Malkyl, aryld^alkyloxy- carbonyl, d^alkylcarbonyl, C3_-7cycloalkylcarbonyl, C_3-7cycloalkyl- Cι-₄alkyloxycarbonyl, C_3-7cycloalkylcarbonyloxy, carboxylC_1- alkyl- carbonyloxy, arylcarbonyloxy, aryloxycarbonyloxy, Het¹ carbonyl, He^carbonyloxy, optionally substituted with aryl, aryloxy, Het² , halogen or hydroxy; wherein the substituents on the amino groups are each independently selected from C_1- alkyl, aryl, arylC_1- alkyl,

C_3-7cycloalkyl, and He^d^alkyl; Rπ is hydrogen, C_3-7cycloalkyl, C_2-6alkenyl, C_2-6alkynyl, aryl, Het , Het or C_1-4alkyl optionally substituted with halogen, hydroxy, C_1-4alkylS(=O)_t,

1 9 aryl, C_3- cycloalkyl, Het , Het , amino optionally mono- or disubstituted where the substituents are each independently selected from C_1-4alkyl, aryl, arylC_1- alkyl, C_3- cycloalkyl, C_3- cycloalkylC_1- alkyl, Het¹, Het², He^Cwalkyl and Het²C_1-4alkyl; whereby Ru_b may be linked to the remainder of the molecule via a sulfonyl group; each independently, t is zero, 1 or 2; R is hydrogen or C_1-6alkyl; L is -C(=O)-, -O-C(=O)-, -NRs-C(=0)-, -O-C_1-6alkanediyl-C(=O)-,

-NR₈-d_-6alkanediyl-C(=O)-, -S(=O)₂-, -O-S(=O)₂-, -NR₈-S(=O)₂ whereby either the C(=O) group or the S(=0)₂ group is attached to the NR₂ moiety; whereby the Ci.6alkanediyl moiety is optionally substituted with aryl, Het¹ or Het²;

R₃ is Ci-₆alkyl, aryl, C_3-7cyclo alkyl, C_3- cycloalkylC_1- alkyl, or arylC_1-4alkyl; R₄ is hydrogen, C_1-4alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(Ci alkyl)aminocarbonyl, C3_-7cycloalkyl, C _-6alkenyl, C_2-6alkynyl, or Ci_-6alkyl optionally substituted with one or more substituents each independently selected from aryl, Het¹, Het², C_3- cycloalkyl, Ci^alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(C_1-4alk l)aminocarbonyl, aminosulfonyl, C_1- alkylS(=O)_t, hydroxy, cyano, halogen and amino optionally mono- or disubstituted where the substituents are each independently selected from Ci^alkyl, aryl, arylC_1- alkyl, C_3- cycloalkyl, C_3-7cycloalkylC_1-4alkyl, Het¹, Het², He^C^alkyl and Het²C_1-4alkyl;

A is C_1-6alkanediyl, -C(=O)-, -C(-S)-, -S(=O)₂-, C_1-6aIkanediyl-C(=O)-,

C_1-6alkanediyl-C(=S)- or Cι_-6alkanediyl-S(=O) -; whereby the point of attachment to the nitrogen atom is the Ci_₆alkanediyl group in those moieties containing said group; R₅ is hydrogen, hydroxy, C_1-6alkyl, ammoCι_-6alkyl whereby the amino group may optionally be mono- or di-substituted with C_1- alkyl; R₆ is C_1-6alkyloxy, Het¹, Het¹ oxy, Het², He^oxy, aryl, aryloxy or amino; and in case -A- is other than Cι_₆alkanediyl then R₆ may also be d-βalkyl, Het¹ Chalky!, aryloxyC_1-4alkyl or aminoCi-ealkyl; whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents each independently selected from C_halky! C_1-4alkylcarbonyl, d^alkyloxycarbonyl, aryl, aryl- carbonyl, aryloxycarbonyl, Het¹, Het², arylC_1- alkyl, Het^Malkyl or Het²C_walkyl; and

-A-R₆ may also be hydroxyC_1-6alkyl; R₅ and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het² or Het².

2. A compound according to claim 1, wherein:

R₉ , Rio_a and R₁₀b are, each independently, hydrogen, C_1-4alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(C_1- alkyl)aminocarbonyl, C₃. cyclo- alkyl, C_2-6alkenyL C - alkynyl or C_1-4alkyl optionally substituted with aryl, Het¹, Het², C_3-7cycloalkyl, C_1- alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(C₁ alkyl)aminocarbonyl, aminosulfonyl, Cι-₄alkylS(O)_t, hydroxy, cyano, halogen or amino optionally mono- or disubstituted where the substituents are selected from C_1- alkyl, aryl, aryld^alkyl, C_3-7cycloalkyl,

C_3-7cycloalkylC_1-4alkyl, Het¹, Het², Het'C^alkyl and Het²C_1-4alkyl; whereby R9_J Rioa and the carbon atoms to which they are attached may also form a C₃_₇cycloalkyl radical; Riia is hydrogen, C₂_₆alkenyl, C_2-6alkynyl, C_3- cycloalkyl, aryl, aminocarbonyl optionally mono- or disubstituted, aminoC_1-4alkylcarbonyloxy optionally mono- or disubstituted, carbonyl, He^oxycarbonyl, aryloxycarbonylC g lkyl, arylC_1-4alkyloxy- carbonyl, CMalkylcarbonyl, C _-7cycloalkylcarbonyl, C_3-7cycloalkylCι- alkyl- oxycarbonyl, C3- cycloalkylcarbonyloxy, C_1-4alkylcarbonyloxy, arylcarbonyloxy, aryloxy- carbonyloxy, Het¹ carbonyl, Het²carbonyloxy, Het²C_1- alkylcarbonyloxy, or optionally substituted with aryl, aryloxy, Het² or hydroxy; wherein the substituents on the amino groups are each independently selected from aryl, arylC_1- alkyl, C_3-7cycloalkyl, Het¹,

Het², He^d^alkyl and He^d^alkyl; Rπb is hydrogen, C_3- cycloalkyl, C_2-6alkenyl, C _-6alkynyl, aryl, Het¹, Het² or Chalky! optionally substituted with halogen, hydroxy, C_1-4alkylS(=O)_t, aryl, C₃- cycloalkyl, Het¹, Het², amino optionally mono- or disubstituted where the substituents are selected from Ci^alkyl, aryl, aryld^alkyl, C_3-7cycloalkyl, C₃.₇cycloalkylC_I-4alkyl, Het¹, Het², Het^_Malkyl and He^C^alkyl; whereby Ru_b maybe linked to the remainder of the molecule via a sulfonyl group; t is zero, 1 or 2;

L is -C(=O)-, -O-C(=O)-, -NR₈-C(=O)-, -O-C_1-6alkanediyl-C(=O)-,

-NR₈-C_1-6alkanediyl-C(=O)-, -S(=O)₂-, -O-S(=O)₂-, -NR₈-S(=O)₂ whereby either the C(=O) group or the S(=O)₂ group is attached to the NR₂ moiety; R₄ is hydrogen, Cι_₄alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(Ci_-4alkyl)aminocarbonyl, C_3-7cycloalkyl, C_2-6alkenyl, C_2-6alkynyl, or C^aU yl optionally substituted with one or more substituents selected from aryl, Het¹, Het², C_3- cycloalkyl, C_1- alkyloxycarbonyl, carboxyl, aminocarbonyl, mono- or di(C_1-4alkyl)aminocarbonyl, aminosulfonyl, C_1- alkylS(=O)t, hydroxy, cyano, halogen and amino optionally mono- or disubstituted where the substituents are selected from C_1-4alkyl, aryl, arylCi^alkyl, C_3- cycloalkyl, C_3-7cycloalkyl-

C_Malkyl, Het¹, Het², He^C^alkyl and He^d^alkyl; R₆ is C_1-6alkyloxy, Het¹, Het^!oxy, Het², Het²oxy, aryl, aryloxy or amino; and in case -A- is other than C_1-6alkanediyl then R₆ may also be C_1-6alkyl, He^d^alkyl, Het²C_1- alkyl, Het²oxyC_1- alkyl, arylC_1-4alkyl, aryloxyC_1- alkyl or aminoCi_-6alkyl; whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents selected from C_1-4alkyl, aryl, arylcarbonyl, aryloxycarbonyl, Het¹, Het², arylC_1- alkyl, Het¹C₁ alkyl or Het²C_1-4alkyl.

3. A compound according to any of claim 1 to 2 wherein

Ri is hydrogen, C_1-6alkyl, C_2-6alkenyl, arylCi_₆alkyl, C_3-7cycloalkyl, d^cycloalkyl- C_1-6alkyl, aryl, Het¹, He^d-ealkyl, Het² or Het²Cι-₆alkyl; wherein Het¹ is a saturated or partially unsaturated monocyclic heterocycle having 5 or 6 ring members, which contains one or more heteroatom ring members each independently selected from nitrogen, oxygen or sulfur and which is optionally ^" substituted on one or more carbon atoms.

4. A compound according to any of claims 1 to 3 wherein L is -O-C_1-6alkanediyl- C(=O)-.

5. A compound according to any one of claims I to 4 wherein A is Cι_-6alkanediyl, -C(=O)- or C_1-6aιkanediyl-C(=O)-; whereby the point of attachment to the nitrogen atom is the Cι_-6alkanediyl group in those moieties containing said group; R₅ is hydrogen, d.₆alkyl, Het¹C_1-6alkyl, Het^d-ealkyl, aminoC_1-6alkyl whereby " the amino group may optionally be mono- or di-substituted with C_1-4alkyl; and in case -A- is -C(=O)- then R₆ is Cι_-6alkyloxy, Het¹, Het y or Het²oxy, aryl,

in case -A- is d^alkanediyl then R₆ is amino, Ci-βalkyloxy, Het¹, Het y or

Het²oxy; and in case -A- is Ci.₆alkanediyl-C(=O)- then R is C_1-6alkyloxy, Het¹, Het¹ oxy or Het²oxy, aryl, Ci_₆alkyl, He^d^alkyl, HetVyd^alkyl, He^C_Malkyl, Het²oxyC galkyl, arylC_1- alkyl, or aminoCι_-4alkyl; whereby each of the amino groups in the definition of R₆ may optionally be substituted with one or more substituents selected from C_1- alkyl, C_1-4alkyl- carbonyl, C_1-4alkyloxycarbonyl, aryl, arylcarbonyl, aryloxycarbonyl, Het¹, Het², arylC_1-4alkyl, or Het²C_1-4alkyl; and R₅ and -A-R₆ taken together with the nitrogen atom to which they are attached may also form Het¹ whereby Het¹ is substituted by a least an oxo group.

6. A compound according to any of claims 1 to 3, wherein

Ri is Het² or wherein said Het² is an aromatic heterocycle having at least one heteroatom each independently selected from nitrogen, oxygen and sulfur; and L is -C(=O)-, -O-C(=O)- or -O-C_1-6alkyl-C(=O)-.

7. A compound according to any of claims 1 to 3, wherein

Ri is Het² or wherein said Het² is an aromatic heterocycle having at least two heteroatom each independently selected from nitrogen, oxygen and sulfur; and L is -C(=O)-, -O-C(-O)- or -O-C_1-6alkyl-C(=O)-.

8. A compound according to any of claims 1 to 4, wherein A is Cι_-6alkanediyl or -C(=O)-;

R₅ is hydrogen or methyl; and R_ is C_1-6alkyloxy, Het¹, Het², amino or amino Cι- alkyl; whereby each amino optionally may be mono- or disubstituted where the substituents are each independently selected from C_1- alkyl, aryl, aryld^alkyl, C_3- cycloalkyl, C₃-₇cycloalkylCi alkyl, Het¹, Het², Het^d^alkyl and He^C^alkyl.

9. A compound according to any of claims 1 to 3, wherein

Ri is Het² or He d-βalkyl; wherein said Het² is an aromatic heterocycle having at least one heteroatom each independently selected from nitrogen, oxygen and sulfur; L is -C(=O)-, -O-C(=O)- or -O-Cι_-6alkyl-C(=O)-; A is C_1-6alkanediyl or -C(=O)-;

R₅ is hydrogen or methyl; and

R₆ is Ci_-6alkyloxy, Het¹, Het², amino or amino Ci_-6alkyl; whereby each amino optionally may be mono- or disubstituted, where the substituents are each independently selected from C_3- cyclo alkyl, Het¹, Het², and Het²C_1-4aIkyl.

10. A compound according to any of claims 1 to 3, wherein,

Ri is 2-thiazolylmethyl-; and L is -O-C(=O)-.

11. A compound according to any of claims 1 to 3, wherein R₅ is hydrogen; A is ~C(=O)-; and

R₆ is Het²; wherein said Het² contains 5 or 6 ring members and one heteroatom selected from nifrogen, oxygen or sulfur.

12. A compound according to any of claims 1 to 3, wherein

Ri is Het , having 8 ring members and two heteroatoms each independently selected from nitrogen, oxygen or sulfur; L is -O-C(=O)-; . R₅ is hydrogen or methyl; A is -C =O)- or Ci_-6alkanediyl; and

R₆ is optionally mono- or disubstituted aminoC_1-4alkyl, Het¹, Het²; wherein said Het² contains 5 or 6 ring members and one heteroatom selected from nitrogen, oxygen or sulfur; wherein the amino substituents are each independently selected from C_1-4alkyl, aryl, arylC_1-4alkyl, C_3-7cyclo alkyl, C₃.₇cycloalkylCi alkyl, Het¹, He^ He^Ci^alkyl and He^C_Malkyl.

13. A compound as claimed in any one of claim 1 to 12 in a prodrug form.

14. A compound as claimed in any one of claim 1 to 12 in a pharmaceutically tolerable salt form.

15. A pharmaceutical composition, comprising an effective amount of at least one compound as claimed in any one of claims 1 to 14, and a pharmaceutically tolerable excipient.

16. A compound as claimed in any one of claims 1 to 14 for use as a medicine.

17. A method of inhibiting a protease of a refrovirus in a mammal infected with said refrovirus, comprising a protease inhibiting amount of a compound according to any one of claims 1 to 14 to said mammal in need thereof.

18. A method of treating or combating infection or disease associated with refrovirus infection in a mammal, comprising administering an effective amount of at least one compound according to any one of claims 1 to 14 to said mammal.

19. The methods of claim 17 or 18, wherein said mammal is a human.

20. A method of inhibiting retroviral replication, comprising contacting a refrovirus with an effective amount of at least one compound according to any one of claims 1 to 14.

21. The method of claim 17 or 18 or 19, wherein the refrovirus is a human immunodeficiency viras (HIN).

22. The method as claimed in claim 21, wherein the HIN virus is a multi-drag resistant sfrain.

23. A compound as claimed in any one of claims 1 to 14 for use as a medecine.

24. The use of a compound as claimed in any one of claims 1 to 14 in the manufacture of a medicament for treating or combating infection or disease associated with refrovirus infection in a mammal.

25. The use of a compound as claimed in any one of claims 1 to 14 in the manufacture of a medicament for inhibiting a protease of a refrovirus in a mammal infected with said refrovirus.

26. The use of a compound as claimed in any one of claims 1 to 14 in the manufacture of a medicament for inhibiting retroviral replication.

27. The use of a compound as claimed in any one of claims 24 to 26 wherein the retro viras is a human immunodeficiency virus (HIV).

28. The use of a compound as claimed in any one of claims 24 to 26 wherein the retiovirus is a multi-drag resistant strain.