Intramolecular nucleophilic attack in 6-epi-ampicillin

Abstract

6-Epi-hetacillin slowly hydrolyses in neutral aqueous solution to 6-epi-ampicillin, which then gradually cyclizes to 2-(3,6-dioxo-5-phenylpiperazin-2-yl)-5,5-dimethylthiazolidine-4-carboxylic acid by intramolecular nucleophilic attack of the side-chain amino-group upon the β-lactam carbonyl; under the same conditions hetacillin readily hydrolyses to yield ampicillin as sole product.