| 摘要 |
Compounds of the formula <IMAGE> wherein A is <IMAGE> <IMAGE> R is hydrogen, lower alkyl, benzyl, p-methoxybenzyl, p-nitrobenzyl, diphenylmethyl, tri(lower alkyl)silyl, lower alkoxymethyl, 2,2,2-trichloroethyl, <IMAGE> or <IMAGE> Y is halogen or lower alkoxy; R1 is lower alkyl, phenyl, or substituted phenyl; and X is hydrogen, lower alkanoyloxy, <IMAGE> or certain heterothio groups; R4 is hydrogen or lower alkyl; R5 is lower alkyl; are disclosed. These compounds, particularly the free acids, possess the useful pharmacological property of inhibiting beta -lactamase enzymes as well as being useful as intermediates, particularly where R is a readily cleavable ester, in the preparation of antibacterially active 6 alpha -methoxy penicillins and 7 alpha -methoxy cephalosporins.
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