Preparation and properties of substituted 6β-vinylpenicillanic acids
Abstract
Routes to the title compounds are described, either using the selective addition of thiols to the known 6-allylidenepenicillanic acids or by the conjugate addition of Grignard derivatives, derived from 6,6-di-bromopenicillanates, to substituted acrylates and acrylamides, followed by stereoselective reduction of the remaining 6-bromo-group to produce the 6β-substituted penicillanates. The 6β-derivatives containing the acryloyl side-chain were relatively unstable and readily underwent intramolecular rearrangement to the corresponding thiazepinones.