On the chemistry of β-lactamase inhibition by 6β-bromopenicillanic acid

Abstract

6β-Bromopenicillanic acid, a powerful inhibitor of β-lactamase I from Bacillus cereus, reacts with a serine residue in the enzyme and is bound, via an ester linkage, as the dihydrothiazine (2a). Spectroscopic and chemical evidence is presented for this assignment and the evidence compared to that obtained from the related model dihydrothiazine (2b). Under certain conditions the bound species underwent further chemical changes caused by an autoxidation reaction; the model dihydrothiazine (2b) undergoes similar autoxidation reactions.