Patent ID: 7511034

Claim:
A compound of the following formula (I) or a pharmaceutically acceptable salt thereof: wherein R 1 denotes hydrogen, or a straight or branched acyl; wherein R 2 denotes alkyl, and wherein R 3 denotes CO 2 H, CONH 2 , or CONR 4 R 5 , wherein when R 3 is CO 2 or CONH 2 , R 1 is straight or branched acyl, wherein R 4 denotes hydrogen, alkyl, aralkyl or aryl, and wherein R 5 denotes substituted or unsubstituted heterocyclic radical having 1 to 4 heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur, the heterocyclic radical being selected from the group consisting of furanyl, oxazolyl, isooxazolyl, thiophenyl, thiazolyl, isothiazolyl, pyrrolyl, imidazolyl, pyrazolyl, oxadiazolyl, thiadiazoyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, triazolyl, hydroxyguinolinyl, and tetrazolyl, it being possible for the heterocyclic radical to be substituted once or twice, identically or differently, by halogen, C 1-2 -alkyl, C 1-4 -alkoxy, C 1-4 -alkylthio, hydroxy, mercapto, trifluoromethyl, nitro, phenyl, nitrile, carboxy, carboxylic ethyl ester or C 1-4 -alkoxycarbonyl.