The chemistry of 4-mercaptoazetidin-2-ones. Part 3. Synthesis of 6-phenoxyacetamido-2-alkylidenepenam-3-carboxylic acids

A general method for the preparation of α-bromoallenic esters (2) involving the reaction of an acid chloride with a carboxybromomethylenetriphenylphosphorane has been developed. Reaction of these esters with the 4-mercaptoazetidin-2-one (1) gave rise to the 2-alkylidenepenam esters (3). The title compounds, obtained by hydrogenolysis of the corresponding benzyl esters, showed only moderate antibacterial properties.