| 摘要 |
Compounds of the formula (I): <IMAGE> (I) wherein R1 is hydrogen, lower alkyl, hydroxymethyl or phenyl; R2 is hydrogen, lower alkyl or an optionally salted or esterified carboxyl group; R3 is hydrogen, chlorine, optionally substituted alkyl or a conjugating group; and R4 is a conjugating group, CH2OH or CH(OH)CH3; are useful for their beta -lactamase inhibitory activity and are also useful in symergistic combinations with penicillins or cephalosporins. |
