Racemates, diastereoisomers and optical isomersof a compound of formula (I) wherein B is H, a C6or C10 aryl, C7-16 aralkyl； Het or (lower alkyl)-Het,all of which optionally substituted with C1-6 alkyl；C1-6 alkoxy； C1-6 alkanoyl； hydroxy； hydroxyalkyl；halo； haloalkyl； nitro； cyano； cyanoalkyl； amino optionallysubstituted with C1-6 alkyl； amido； or (loweralkyl)amide； or B is an acyl derivative of formulaR4-C(O)-； a carboxyl of formula R4-O-C(O)-； anamide of formula R4-N(R5)-C(O)-； a thioamide of formulaR4-N(R5)-C(S)-；or a sulfonyl of formula R4-SO2；R5 is H or C1-6 alkyl； and Y is H or C1-6 alkyl； R3 isC1-8 alkyl, C3-7 cycloalkyl, or C4-10 alkylcycloalkyl, alloptionally substituted with hydroxy, C1-6 alkoxy, C1-6thioalkyl, amido, (lower alkyl)amido, C6 or C10 aryl, or C7-16 aralkyl； R2 isCH2-R20, NH-R20, O-R20 or S-R20, wherein R20 is a saturatedor unsaturated C3-7 cycloalkyl or C4-10 (alkylcycloalkyl), all of which beingoptionally mono-, di- or tri-substituted with R21, or R20 is a C6or C10 aryl or C7-14 aralkyl optionally substituted, or R20 is Het or (loweralkyl)-Het, both optionally substituted, Het or (lower alkyl)-Het；carboxyl； carboxy(lower alkyl)； C6 or C10 aryl, C7-14 aralkyl or Het, saidaryl, aralkyl or Het being optionally substituted； and R1 is H；C1-6 alkyl, C3-7 cycloalkyl, C2-6 alkenyl, or C2-6 alkynyl, all optionallysubstituted with halogen； or a pharmaceutically acceptable salt orester thereof.
