Penam derivatives

摘要

A compound of the general formula: <IMAGE> wherein R1 is amino or a conventional, pharmaceutically acceptable acylamino, R2 is carboxy or a conventionally protected carboxy, X is -S- or <IMAGE> R3 is lower alkyl and Y'' is a residue of a strong nucleophile selected from the group consisting of azido, thiocyanato, lower alkyanoylthio and piperidinothiocarbonylthio.