| abstract |
Disclosed are 2β-substituted-methylpenicillanic acid compounds of the formula ##STR1## wherein n is 0, 1 or 2; and ##STR2## is monocyclic or bicyclic heterocyclic ring group which has 2 to 4 nitrogen atoms as hetero atom in its ring structure and which may be optionally substituted with alkyl, alkoxycarbonyl, phenyl, formyl or benzyloxycarbonyl optionally having alkyl, nitro or a halogen atom on the benzene ring, with the proviso that said heterocyclic ring group is not 1,2,3-triazol-1-yl; or salts or esters thereof. n These compounds are useful as β-lactamase inhibitor. |