Compounds of the formula (I): ##STR1## wherein R.sub.1 is hydrogen, lower alkyl, hydroxymethyl or phenyl; R.sub.2 is hydrogen, lower alkyl or an optionally salted or esterified carboxyl group; R.sub.3 is hydrogen, chlorine, optionally substituted alkyl or a conjugating group; and R.sub.4 is a conjugating group, CH.sub.2 OH or CH(OH)CH.sub.3 ; are useful for their .beta.-lactamase inhibitory activity and are also useful in symergistic combinations with penicillins or cephalosporins.
式(I)的化合物:##
STR1##其中R.sub.1是
氢、低
碳烷基、
羟甲基或
苯基;R.sub.2是
氢、低
碳烷基或一个可选择盐化或
酯化的羧基;R.sub.3是
氢、
氯、可选择取代的烷基或一个共轭基团;R.sub.4是一个共轭基团、CH.sub.2 OH或CH(OH)CH.sub.3;这些化合物对其β-内
酰胺酶抑制活性很有用,并且与
青霉素或
头孢菌素的协同组合也很有用。