A compound of the formula: ##STR1## wherein R.sup.1 is (C.sub.1 to C.sub.6) alkyl, R.sup.2 is a carboxy or a protected carboxy group, R.sup.3 is amino or a protected amino group and A is hydroxyimino (C.sub.1 to C.sub.6) alkylene or (C.sub.1 to C.sub.6)-alkoxyimino (C.sub.1 to C.sub.6)alkylene, And pharmaceutically acceptable salt thereof.
一种化合物的公式:##STR1## 其中R.sup.1为(C.sub.1到C.sub.6)烷基,R.sup.2为羧基或保护羧基,R.sup.3为
氨基或保护
氨基,A为羟
亚胺基(C.sub.1到C.sub.6)烷基或(C.sub.1到C.sub.6)烷氧基
亚胺基(C.sub.1到C.sub.6)烷基,以及其药学上可接受的盐。