Synthesis and β-lactamase inhibitory activity of new 6β-cysteinesulfonamidopenicillanic acids Original Research Article

New 6β-cysteinesulfonamidopenicillanic acids and their sulfoxides were synthesized by sulfonylation of 6β-aminopenicillanic acid or its (S)-sulfoxide with (R)-N-benzyloxycarbonylcysteinesulfonyl chloride ethyl ester (, ) and (R)-N-benzyloxycarbonylcysteinesulfonyl chloride benzyl ester (, ). The corresponding 6β-cysteinesulfonamidopenicillanic acids sulfones and were prepared by oxidation of the sulfoxides and with potassium permanganate in aqueous medium. When combined with ampicillin some of the compounds reduced the minimal inhibitory concentrations of ampicillin against β-lactamase producing strains.