Synthesis of antibacterial pen-2-em-3-carboxylic acids from clavulanic acid

Abstract

The antibacterially active potassium salt (7b) has been synthesised from clavulanic acid (1a) by two routes involving either base-catalysed or thermolytic cyclisations of novel monocyclic azetidinones; protection of the hydroxy group of clavulanic acid followed by an analogous thermolytic cyclisation gave the corresponding 2-hydroxyethylpen-2-em ester (7d) from which a series of antibacterially active O-substituted derivatives was available.