| 摘要 |
A compound of formula I <IMAGE> I wherein X is sulfur or CH2; R1 is hydrogen, hydroxy, amino, C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, phenyl optionally substituted with one to three C1-6 alkyl, C1-6 alkyloxy or hydroxy, C1-6 alkylthio, phenylthio optionally substituted with one to three C1-6 alkyl or C1-6 alkyloxy on the phenyl ring, phenylmethyloxy optionally substituted with one to three C1-6 alkyl or C1-6 alkyloxy on the phenyl ring, 1-morpholino, C1-6 alkyloxy, C2-6 alkenylmethyloxy, C3-6 alkynylmethyloxy, C1-6 alkylamino, C1-6 dialkylamino or a radical selected from the group consisting of <IMAGE> <IMAGE> in which n is 0 to 3, R5 is C1-6 alkyl or hydrogen, and R3 and R4 are independently C1-6 alkyl; R2 is hydrogen, a conventional amino protecting group or an acyl group; R0 is hydrogen or a conventional carboxy protecting group, or -CO2R0 taken together forms a physiologically hydrolyzable ester; or pharmaceutically acceptable salts or solvates thereof.
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