A compound of the general formula: ##STR1## wherein R.sup.1 is amino or a conventional, pharmaceutically acceptable acylamino, R.sup.2 is carboxy or a conventionally protected carboxy, X is --S-- or ##STR2## R.sup.3 is lower alkyl and Y" is a residue of a strong nucleophile selected from the group consisting of azido, thiocyanato, lower alkyanoylthio and piperidinothiocarbonylthio.
一种通用式为:##STR1##的化合物,其中R.sup.1是
氨基或传统的、药学上可接受的酰胺基,R.sup.2是羧基或传统保护的羧基,X是--S--或##STR2##,R.sup.3是较低的烷基,Y"是从偏氮、
硫氰酸、较低的酰
硫基和
哌啶硫氨酰
硫中选择的强亲核剩余基。