Inhibitors of protein tyrosine phosphatases

1. A compound of the formula:

wherein R 1 and R 2 are the same or different and each individually is a residue of a carboxylic acid, and pharmaceutically acceptable salts thereof, wherein said carboxylic acid is selected from the group consisting of:

3-dimethylaminobenzoic acid, 2-(2-cyanophenylthio)benzoic acid, 2-(4-chlorobenzoyl)benzoic acid, (−)-2-oxo-4-thiazolidine-carboxylic acid, (−)-N-acetylneuraminic acid, (+)-6-methoxy-a-methyl-2-naphthaleneacetic acid, (+)-carbobenzyloxy-D-proline, (+)-menthoxyacetic acid, (+)-2-(2-chlorophenoxyl)propionic acid, (±)-1-methyl-2-cyclohexene-1-carboxylic acid, (1-naphthoxy)acetic acid, (1R)-(1a,2b,3a)-(+)-3-methyl-2-nitromethyl-5-oxocyclopentaneacetic acid, (1R,4R)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptane-1-carboxylic acid, (1S)-(+)-camphanic acid, (1S,3R,4S,5R)-1,3,4,5-tetrahydroxycyclohexanecarboxylic acid, (2,4-di-tert-pentylphenoxyl)acetic acid, (2-naphthoxy)acetic acid, (2-pyrimidylthio)acetic acid, (4-carboxybutyl)triphenyl-phosphonium bromide, (4-chlorophenylthio)acetic acid, (4-methylphenoxy)acetic acid, (a,a,a-trofluoro-m-tolyl)acetic acid, (E)-2-((4-hydroxyphenyl)diazenyl)benzoic acid, (E)-2-methyl-3-(2,4,5-trimethoxyphenyl)acrylic acid, (methylthio)acetic acid, (R)-(−)-2-hydroxy-4-phenylbutyric acid, (R)-(−)-3-chloromandelic acid, (R)-(−)-hexahydromandelic acid, (R)-(+)-2-pyrrolidone-5-carboxylic acid, (R)-(+)-citronellic acid, (R)-2-(1-phenylethylcarbamoyl)benzoic acid, (R)-2-hydroxy-2-phenylacetic acid, (R)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoic acid, (R)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, (S)-(−)-indoline-2-carboxylic acid, (S)-(+)-2-oxo-4-phenyl-3-oxazolidineacetic acid, (S)-(+)-5-oxo-2-tetrahydro-furancarboxylic acid, (S)-(+)-hexahydromandelic acid, (S)-(+)-N-[1-(1-naphthyl)-ethyl]-phthalamic acid, (S)-(+)-O-acetylmandelic acid, (S)-2-(1-phenylethylcarbamoyl)benzoic acid, (S)-2-(4-isobutylphenyl)propanoic acid, (S)-2-(phenylcarbamoyloxy)propanoic acid, (S)-3-(benzyloxycarbonyl)-2-oxoimidazolidine-4-carboxylic acid, (S)-3,3,3-trifluoro-2-methoxy-2-phenylpropanoic acid, (S)-6-methoxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, (trimethylsilyl)acetic acid, (z)-2-cyano-3-(3-hydroxyphenyl)acrylic acid, 1-(4-chlorophenyl)-1-cyclopentanecarboxylic acid, 1-(tert-butyl)hydrocinnamic acid, 1,2-phenylenedioxydiacetic acid, 1,4-dihydro-2-methylbenzoic acid, 1,4-dihydroxy-2-naphthoic acid, 10-hydroxydecanoic acid, 10-undecynoic acid, 1-admantanecarboxylic acid, 1-cyano-1-cyclopropane-carboxylic acid, 1-hydroxy-2-naphthoic acid, 1-isoquinolinecarboxylic acid, 1-methyl-(1S,2R)-(+)-cis-1,2,3,6-tetrahydrophthalate, 1-methyl-1-cyclohexane-carboxylic acid, 1-methyl-1H-indole-2-carboxylic acid, 1-methyl-2-pyrrolecarboxylic acid, 1-methylcyclopropane-carboxylic acid, 1-naphthoic acid, 1-phenyl-1-cyclopentane-carboxylic acid, 1-phenyl-1-cyclopropane-carboxylic acid, 1-pyreneacetic acid, 1-pyrenebutyric acid, 1-pyrenecarboxylic acid, 241R,2R,3R,4S)-3-hydroxy-4,7,7-trimethylbicyclo[2.2.1]heptan-2-yl)acetic acid, 2-((benzyloxycarbonyl)(methyl)amino)-2-methylpropanoic acid, 2-(2,(trifluoromethyl)phenyl)acetic acid, 2-(2,4,5-trichlorophenoxy)-propionic acid, 2-(2,4-dichlorophenoxy)-propionic acid, 2-(3,5-dinitrobenzamido)-2-phenylacetic acid, 2-(3,5-dinitrobenzamido)-4-methylpentanoic acid, 2-(3-chlorophenoxyl)propionic acid, 2-(4-(trifluoromethyl)phenyl)acetic acid, 2-(4-chloro-3-nitrobenzoyl)-benzoic acid, 2-(4-chlorophenoxy)-2-methyl-propionic acid, 2-(4-chlorophenoxyl)propionic acid, 2-(4-fluorobenzoyl)benzoic acid, 2-(4-hydroxy-3-methoxyphenyl)acetic acid, 2-(4-hydroxyphenoxy)-propionic acid, 2-(4-isobutylphenyl)propanoic acid, 2-(4-nitrophenyl)propionic acid, 2-(benzyloxycarbonylamino)-3-(1H-indol-3-yl)propanoic acid, 2-(trifluoromethyl)acrylic acid, 2-(trifluoromethyl)benzoic acid, 2-(trifluoromethyl)cinnamic acid, 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid, 2,2-bis(hydroxymethyl)-propionic acid, 2,3,4,5,6-pentafluoro-cinnamic acid, 2,3,4,5,6-pentafluorophenoxy acetic acid, 2,3,4,5,6-pentafluorophenyl-acetic acid, 2,3,4,5-tetrafluorobenzoic acid, 2,3,4-trifluorocinnamic acid, 2,3,4-trihydroxybenzoic acid, 2,3,4-trimethoxybenzoic acid, 2,3,5,6-tetrafluoro-4-hydr-oxy-benzoic acid hydrate, 2,3,5,6-tetrafluorobenzoic acid, 2,3,5,6-tetrafluoro-p-toluic acid, 2,3,5-triiodobenzoic acid, 2,3,6-trifluorobenzoic acid, 2,3-dichlorobenzoic acid, 2,3-difluorobenzoic acid, 2,3-dihydroxybenzoic acid, 2,3-dimethylbenzoic acid, 2,4,5-trichlorophenoxyacetic acid, 2,4,5-trimethoxybenzoic acid, 2,4,6-trichlorobenzoic acid, 2,4,6-trifluorobenzoic acid, 2,4,6-trihydroxybenzoic acid monohydrate, 2,4,6-trimethylbenzoic acid, 2,4-bis(trifluoromethyl)-benzoic acid, 2,4-dichloro-5-fluorobenzoic acid, 2,4-dichloro-5-sulfamoyl-benzoic acid, 2,4-dichlorobenzoic acid, 2,4-dichlorophenylacetic acid, 2,4-difluorobenzoic acid, 2,4-difluorophenylacetic acid, 2,4-dihydroxybenzoic acid, 2,4-dimethylbenzoic acid, 2,4-dinitrobenzoic acid, 2,4-dinitrophenylacetic acid, 2,4-hexadienoic acid, 2,5-bis(trifluoromethyl)-benzoic acid, 2,5-dichlorobenzoic acid, 2,5-difluorobenzoic acid, 2,5-difluorophenylacetic acid, 2,5-dihydroxybenzoic acid, 2,5-dihydroxyphenylacetic acid, 2,5-dimethoxybenzoic acid, 2,5-dimethoxycinnamic acid, 2,6-dichloro-3-nitrobenzoic acid, 2,6-difluorobenzoic acid, 2,6-difluorophenylacetic acid, 2,6-dihydroxybenzoic acid, 2,6-dimethoxynicotinic acid, 2,6-dimethylbenzoic acid, 2,6-heptadienoic acid, 2-[4-(dibutylamino)-2-hydroxy-benzoyl]benzoic acid, 2-bibenzylcarboxylic acid, 2-biphenylcarboxylic acid, 2-bromo-3-nitrobenzoic acid, 2-bromo-4,5-dimethoxybenzoic acid, 2-bromo-5-methoxybenzoic acid, 2-bromo-5-nitrobenzoic acid, 2-bromoacrylic acid, 2-bromophenylacetic acid, 2-chloro-3-nitrobenzoic acid, 2-chloro-4,5-difluorobenzoic acid, 2-chloro-4-fluorobenzoic acid, 2-chloro-5-(methylthio)-benzoic acid, 2-chloro-5-(trifluoro-methyl)benzoic acid, 2-chloro-5-nitrobenzoic acid, 2-chloro-5-nitrocinnamic acid, 2-chloro-6-fluorobenzoic acid, 2-chloro-6-fluorophenylacetic acid, 2-chloro-6-methylnicotinic acid, 2-chlorobenzoic acid, 2-chloronicotinic acid, 2-chlorophenylacetic acid, 2-chloropropionic acid, 2-ethoxy-1-naphthoic acid, 2-ethoxybenzoic acid, 2-ethyl-2-hydroxybutyric acid, 2-ethylbutyric acid, 2-ethylhexanoic acid, 2-ethylthio-2,2-diphenyl-acetic acid, 2-fluoro-3-(trifluoromethyl)-benzoic acid, 2-fluoro-4-(trifluoromethyl)-benzoic acid, 2-fluoro-5-methylbenzoic acid, 2-fluoro-5-nitrobenzoic acid, 2-fluoro-6-(trifluoromethyl)-benzoic acid, 2-fluorobenzoic acid, 2-fluorocinnamic acid, 2-fluorophenylacetic acid, 2-hydroxy-3-isopropyl-6-methylbenzoic acid, 2-hydroxy-3-isopropylbenzoic acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxy-6-isopropyl-3-methylbenzoic acid, 2-hydroxycaproic acid, 2-hydroxyhippuric acid, 2-hydroxyisobutyric acid, 2-hydroxyisobutyric acid, 2-hydroxynicotinic acid, 2-hydroxyphenylacetic acid, 2-iodobenzoic acid, 2-mercaptonicotinic acid, 2-methoxy-2-phenylacetic acid, 2-methoxy-4-(methylthio)-benzoic acid, 2-methoxy-4-nitrobenzoic acid, 2-methoxyphenylacetic acid, 2-methyl-1-cyclohexane-carboxylic acid (cis and trans), 2-methyl-3-nitrobenzoic acid, 2-methyl-3-phenylpropanoic acid, 2-methyl-4-oxo-4-phenylbutyric acid, 2-methyl-6-nitrobenzoic acid, 2-methylbutyric acid, 2-methylcinnamic acid, 2-methylcyclopropane-carboxylic acid (cis&trans), 2-methylhexanoic acid, 2-methylhippuric acid, 2-methylhydrocinnamic acid, 2-methylvaleric acid, 2-naphthoic acid, 2-naphthylacetic acid, 2-nitro-4-(trifluoromethyl)benzoic acid, 2-nitrobenzoic acid, 2-norbornaneacetic acid, 2-oxo-6-pentyl-2H-pyran-3-carboxylic acid, 2-phenoxybenzoic acid, 2-phenoxybutyric acid, 2-phenoxypropionic acid, 2-propylpentanoic acid, 2-quinoxalinecarboxylic acid, 2-thiopheneacetic acid, 2-thiopheneacetic acid, 2-thiopheneglyoxylic acid, 3-(2-hydroxyphenyl)propionic acid, 3-(2-thienyl)acrylic acid, 3-(3,4,5-trimethoxyphenyl)-propionic acid, 3-(3,4-dimethoxyphenyl)-propionic acid, 3-(3-hydroxy-2,4,6-triiodophenyl)pentanoic acid, 3-(3-hydroxyphenyl)-propionic acid, 3-(3-methoxyphenyl)propionic acid, 3-(4-chlorobenzoyl)propionic acid, 3-(4-chlorobenzoyl)propionic acid, 3-(4-chlorobenzoyl)propionic acid, 3-(4-fluorobenzoyl)propionic acid, 3-(4-hydroxyphenyl)propionic acid, 3-(phenylsulfonyl)propionic acid, 3-(trifluoromethyl)cinnamic acid, 3-(trimethylsilyl)propynoic acid, 3,3,3-triphenylpropionic acid, 3,4-(methylenedioxy)cinnamic acid, 3,4-(methylenedioxy)phenyl-acetic acid, 3,4-dichlorobenzoic acid, 3,4-dichlorophenoxyacetic acid, 3,4-diethoxybenzoic acid, 3,4-difluorobenzoic acid, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyhydrocinnamic acid, 3,4-dihydroxyphenylacetic acid, 3,5,6-trichlorosalicylic acid, 3,5-bis(trifluoromethyl)-phenyl acetic acid, 3,5-dibromobenzoic acid, 3,5-dichlorosalicyclic acid, 3,5-difluorocinnamic acid, 3,5-dihydroxy-2-naphthoic acid, 3,5-dinitrobenzoic acid, 3,5-dinitro-o-tuluic acid, 3,5-dinitro-p-toluic acid, 3,5-dinitrosalicyclic acid, 3,5-di-tert-butyl-4-hydroxy-benzoic acid, 3,5-di-tert-butylbenzoic acid, 3,7-dihydroxy-2-naphthoic acid, 3,thiopheneacetic acid, 3-benzoyl-2-pyridine-carboxylic acid, 3-benzoylbenzoic acid, 3-bromo-4-fluorobenzoic acid (95%), 3-bromo-4-methylbenzoic acid, 3-bromo-5-iodobenzoic acid, 3-bromobenzoic acid, 3-bromocinnamic acid, 3-carboxy-PROXYL, 3-chloro-2-nitrobenzoic acid, 3-chloro-4-fluorobenzoic acid, 3-chloro-4-hydroxyphenyl-acetic acid, 3-chlorosalicylic acid, 3-cyanobenzoic acid, 3-fluoro-2-methylbenzoic acid, 3-fluoro-4-hydroxy-phenylacetic acid, 3-fluoro-4-methoxybenzoic acid, 3-fluorophenylacetic acid, 3-furoic acid, 3-hydroxy-2-naphthoic acid, 3-hydroxy-2-quinoxaline-carboxylic acid, 3-hydroxy-4-methoxybenxoic acid, 3-hydroxy-4-methoxy-cinnamic acid, 3-hydroxy-4-nitrobenzoic acid, 3-hydroxybenzoic acid, 3-hydroxybutyric acid, 3-hydroxyphenylacetic acid, 3-indolebutyric acid, 3-indoleglyoxylic acid, 3-indolepropionic acid, 3-iodo-4-methylbenzoic acid, 3-iodobenzoic acid, 3-isoquinolinecarboxylic acid hydrate, 3-methoxy-4-nitrobenzoic acid, 3-methoxycyclohexane-carboxylic acid (cis&trans), 3-methyl-2-phenyvaleric acid, 3-methylhippuric acid, 3-methylindene-2-carboxylic acid, 3-methylsalicylic acid, 3-methyl valeric acid, 3-nitreobenzoic acid, 3-nitrophenylacetic acid, 3-nitropropionic acid, 3-noradamantanecarboxylic acid, 3-oxo-1-indancarboxylic acid, 3-phenoxybenzoic acid, 3-phenylbutyric acid, 3-p-tolylpropanoic acid, 3-thiophenecarboxylic acid, 4-(1,3-dioxoisoindolin-2-yl)-2-hydroxybutanoic acid, 4-(2,4,5-trichlorophenoxy)-butyric acid, 4-(2,4-dichlorophenoxy)-butyric acid, 4-(2,4-di-tert-pentylphenoxy)butyric acid, 4-(2-phenoxyethoxyl)benzoic acid, 4-(3,4-dimethoxyphenyl)-butyric acid, 4-(4-methoxyphenyl)butyric acid, 4-(4-nitrophenyl)butyric acid, 4-(diethylamino)benzoic acid, 4-(dimethylamino)cinnamic acid, 4-(dimethylamino)phenyl-acetic acid, 4-(ethylthio)benzoic acid, 4-(hydroxymethyl)benzoic acid, 4-(methylsulfonyl)benzoic acid, 4-(methylthio)benzoic acid, 4-(methylthio)phenylacetic acid, 4-(trifluoromethoxy)benzoic acid, 4′-(trifluoromethyl)biphenyl-2-carboxylic acid, 4-(trifluoromethyl)mandelic acid, 4,4,4-trifluoro-3-methyl-2-butenoic acid, 4,4-bis(4-hydroxyphenyl)-valeric acid, 4,5-dimethoxy-2-nitrobenzoic acid, 4,6-dioxoheptanoic acid, 4-[4-(2-carboxybenzoyl)-phenyl]butyric acid, 4-acetamidobenzoic acid, 4-acetylbenzoic acid, 4-acetylphenoxyacetic acid, 4-benzyloxy-3-methoxyphenyl-acetic acid, 4-biphenylacetic acid, 4-bromo-3,5-dihydroxy-benzoic acid, 4-bromobenzoic acid, 4-bromocinnamic acid, 4-bromophenylacetic acid, 4-butoxybenzoic acid, 4-butoxyphenylacetic acid, 4-butylbenzoic acid, 4-chloro-2,5-difluorobenzic acid, 4-chloro-3-sulfamoylbenzoic acid, 4-chlorobenzoic acid, 4-chloro-o-tolyloxyacetic acid, 4-chlorophenylacetic acid, 4-chlorosalicylic acid, 4-ethoxycarbonyloxy-3,5-dimethoxybenzoic acid, 4-ethoxyphenylacetic acid, 4-ethylbenzoic acid, 4′-ethylbiphenyl-4-carboxylic acid, 4-fluorenecarboxylic acid, 4-fluoro-1-naphthoic acid, 4-fluoro-2-(trifluoromethyl)-benzoic acid, 4-fluoro-3-nitrobenzoic acid, 4-fluorobenzoic acid, 4-fluorobenzoic acid, 4-fluorocinnamic acid, 4-fluorophenoxyacetic acid, 4-heptyloxybenzoic acid, 4-hexylbenzoic acid, 4-hexyloxybenzoic acid, 4-hydroxy-3-(morpholino-methyl)benzoic acid hydrate, 4-hydroxy-3,5-dinitrobenzoic acid, 4-hydroxy-3-methoxy-benzoic acid, 4-hydroxy-3-methoxy-mandelic acid, 4-hydroxy-3-nitrobenzoic acid, 4-hydroxy-3-nitrophenylacetic acid, 4-hydroxybenzoic acid, 4′-hydroxybiphenyl-4-carboxylic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenylacetic acid, 4-hydroxyphenylpyruvic acid, 4-iodobenzoic acid, 4-isopropoxybenzoic acid, 4-methoxy-3-nitrobenzoic acid, 4-methoxycyclohexane-carboxylic acid, 4-methoxysalilcylic acid, 4-methyl-1-cyclohexane-carboxylic acid (cis and trans), 4-methyl-3-nitrobenzoic acid, 4-methylhippuric acid, 4-methylsalicyclic acid, 4-methylvaleric acid, 4-nitro-3-pyrazolecarboxylic acid, 4-nitrohippuric acid, 4-nonyloxybenzoic acid, 4-Octylbenoic acid, 4-oxo-4H-1-benzopyran-2-carboxylic acid, 4-oxo-6-phenyl-5-hexenoic acid, 4-pentenoic acid, 4-pentylbenzoic acid, 4-pentylbicyclo[2.2.2]octane-1-carboxylic acid, 4-pentyloxybenzoic acid, 4-pentynoic acid, 4-phenylbutyric acid, 4-Propoxybenzoic acid, 4-propylbenzoic acid, 4-pyrazolecarboxylic acid, 4-tert-butylbenzoic acid, 4-tert-butylcyclohexanecarboxylic acid, 4-Vinylbenzoic acid, 5-(4-chlorophenyl)-2-furoic acid, 5,6-dichloronicotinic acid, 5-bromo-2,4-dihydroxybenzoic acid, 5-fluoro-2-methylbenzoic acid, 5-fluoroindole-2-carboxylic acid, 5-fluorosalicylic acid, 5-hydantoinacetic acid, 5-hydroxy-2-indole-carboxylic acid, 5-methoxy-1-indanone-3-acetic acid, 5-methoxy-2-methyl-3-indoleacetic acid, 5-methoxy-2-nitrobenzoic acid, 5-methoxysalicylic acid, 5-methyl-2-nitrobenzoic acid, 5-methyl-2-pyrazine-carboxylic acid, 5-nitro-2-furoic acid, 5-nitro-3-pyrazolecarboxylic acid, 5-phenyl valeric acid, 6-(carbobenzyloxyamino)-caproic acid, 6-acetamidohexnoic acid, 6-bromohexanoic acid, 6-chloronicotinic acid, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, 6-methylchromone-2-carboxylic acid, 6-methylnicotinic acid, 6-nitrocaproic acid, 6-oxoheptaoic acid, 6-phenylhexanoic acid, 7-(carboxymethyoxy)-4-methylcoumarin, 7-hydroxycoumarin-4-acetic acid, 7-methoxy-2-benzofuran-carboxylic acid, 7-methoxycoumarin-4-acetic acid, 7-oxoctanoic acid, 9-anthracenecarboxylic acid, 9-fluoreneacetic acid, 9-fluorenone-1-carboxylic acid, A,a,a-trifluoro-m-toluic acid, a-acetamidocinnamic acid, abietic acid, acetic acid, acetic acid, acetic acid, acetyl-L-asparagine, acetylsalicyclic acid, acetylsalicylic acid, a-cyano-4-hydroxycinnamic acid, adipic acid monoethyl ester, a-hydroxyhippuric acid, anthranilic acid, anti-3-oxotricyclo[2.2.1.02,6]heptane-7-carboxylic acid, a-phenylcyclopentaneacetic acid, a-phenyl-o-toluic acid, Atrolactic acid, benzilic acid, benzotriazole-5-carboxylic acid, benzoylformic acid, bis(4-chlorophenyl)acetic acid, carbobenzyloxy-DL-alanine, carbobenzyloxy-L-alanine, carbobenzyloxy-1-glutamine, carbobenzyloxy-L-valine, cis-2-methoxycinnamic acid, Crotonic acid, cyclohexanebutyric acid, cyclohexanecarboxylic acid, cyclohexanepentanoic acid, cyclohexanepropionic acid, cyclopentylacetic acid, D,L-3,4-dihydroxymandelic acid, D-3-phenyllactic acid, decanoic acid, dicyclohexylacetic acid, diethylphosphonoacetic acid, dikegulac hydrate, diphenylacetic acid, fumaric acid monoethyl ester, fumaric acid, gallic acid, geranic acid, glycolic acid, heptadecafluorononanoic acid, heptanoic acid, hexanoic acid, hippuric acid, hydrocinnamic acid, indole-3-carboxylic acid, indole-4-carboxylic acid, isovaleric acid, L-3-phenyllactic acid, Laurie acid, L-Lactic acid (85%), maleamic acid, methoxyacetic acid, mono-(1R)-(−)-menthyl phthalate, mono-(1S)-(+)-menthyl phthalate, mono-methyl cis-5-norbornene-endo-2,3-dicarboxylate, mono-methyl phthalate, mono-methylterephthalate, N-(2-furoyl)glycine, n-(3,5-dinitrobenzoyl)-DL-a-phenylglycine, N-(3-indolylacetyl)-L-alanine, N-(3-indolylacetyl)-L-isoleucine, N-(3-indolylacetyl)-L-leucine, N-(3-indolylacetyl)-L-phenylalanine, N-(3-indolylacetyl)-L-valine, N-(carbobenzyloxy)-1-phenyl-alanine, N,N-diethyl-3,6-difluoro-phthalamic acid, N-[(R)-1-(1-naphthyl)ethyl]-phthalamic acid, N-[5-(trifluoromethyl)-2-pyridyl]-L-valine, n-acetyl-4-fluoro-DL-phenylalanine, N-acetyl-DL-tryptophan, n-acetyl-1-leucine, N-acetyl-L-methionine, N-acetyl-L-phenylalanine, N-acetyl-L-phenylalanine, n-acetyl-1-tyrosine, N-benzoyl-(2R,3S)-3-phenyl-isoserine, N-benzoyl-L-threonine, N-carbobenzyloxy-2-methyl-alanine, N-carbobenzyloxy-L-glutamic acid 1-methyl ester, N-carbobenzyloxy-L-isoleucine, N-carbobenzyloxy-L-Leucine, n-carbobenzyloxy-1-threonine, n-ethoxycarbonyl-1-phenylalanine, nonanoic acid, N-p-tosylglycine, N-p-tosyl-L-phenylalanine, o-anisic acid, p-anisic acid, pentafluorobenzoic acid, phenoxyacetic acid, phenylacetic acid, podocarpic acid, pyruvic acid, rhodanine-3-acetic acid, S-(thiobenzoyl)thioglycolic acid, s-benzyl-n-carbobenzyloxy-1-cysteine, Sebacic acid monomethyl ester, succinamic acid, succinic 2,2-dimethyl-hydrazide, tetrahydro-2-furoic acid, trans-1-acetyl-4-hydroxy-L-pro line, trans-2,3-dimethoxycinnamic acid, trans-2,4-dichlorocinnamic acid, trans-2,4-difluorocinnamic acid, trans-2,5-difluorocinnamic acid, trans-2,6-difluorocinnamic acid, trans-2-chloro-6-fluro-cinnamic acid, trans-2-hexenoic acid, trans-3-(2,3,5,6-tetramethyl-benzoyl)acrylic acid, trans-3-(2,5-dimethylbenzo-yl)-acrylic acid, trans-3-(4-ethoxy-benzoyl)acrylic acid, trans-3-(4-methoxybenzoyl)-acrylic acid, trans-3-(4-methylbenzoyl)-acrylic acid, trans-3,4-difluorocinnamic acid, trans-3-fluorocinnamic acid, trans-3-furanacrylic acid, trans-3-hexenoic acid, trans-4-chloro-3-nitrocinnamic acid, trans-4-hydroxy-3-methoxy-cinnamic acid, trans-4-hydroxy-3-methoxy-cinnamic acid, trans-4-methyl-1-cyclohexa-ne carboxylic acid, trans-4-pentylcyclohexane carboxylic acid, trans-5-bromo-2-methoxy cinnamic acid, trans-Styrylacetic acid, trans-Styrylacetic acid, tridecafluoroheptanoic acid, trimethylacetic acid, triphenylacetic acid, Valerie acid, and Yohimbinic acid, mono-hydrate.

2. The compound of claim 1 , wherein R 1 or R 2 is

3. The compound of claim 1 , wherein R 1 or R 2 is

4. The compound of claim 1 , wherein R 1 of R 2 is

5. A compound of claim 1 , of the formula

and pharmaceutically acceptable salts thereof.