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A number of new and previously described N-substituted phthalamic acids were used for the N-acylation of 6-aminopenicillanic acid (6-APA). The new 6-APA derivatives thus produced were isolated as sodium or potassium salts. The condensation of phthalamic acid with 6-APA failed to yield the expected product. It was found that both N-carbethoxyphthalamic acid and N-carbethoxyphthalimide afforded the same derivative, namely, 6-phthalimidopenicillanic acid. The antimicrobial activity and penicillinase resistance of the new penicillins described herein are discussed.

Potassium 2 beta-(chloromethyl)-2 alpha-methylpenam-3 alpha-carboxylate 1,1-dioxide (BL-P2013) and its pivaloyloxymethyl ester were prepared by the conversion of 6-aminopenicillanic acid to p-nitrobenzyl 6 alpha-bromo-2,2-dimethylpenam-3 alpha-carboxylate 1-oxide, which was rearranged with benzoyl chloride and quinoline to p-nitrobenzyl 6 alpha-bromo-2 beta-(chloromethyl)-2 alpha-methylpenam-3 alpha-carboxylate in 65% yield. Oxidation and catalytic hydrogenation afforded BL-P2013, which was found to be a potent inhibitor of various bacterial beta-lactamases and has been found to protect amoxicillin from beta-lactamases in both in vitro and in vivo systems.