Simple and condensed β-lactams. Part 5. The synthesis of some (5RS,6SR)-2-(2-formylaminoethylthio)-6-(2-methyl-1,3-dioxolan-2-yl)carbapenem-3-carboxylic acid derivatives and related compounds
Starting with the 4-oxoazetidine-2-carboxylic acids (3a) and (3b), methods for the synthesis of derivatives of the racemic carbapenem-3-carboxylic acid (2), an analogue of the potent antibiotic thienamycin have heen developed. The synthetic steps included chain elongations by the methods of Arndt-Eistert and Masamune, diazo group transfers, oxidative removals of N-protecting 2,4- dimethoxybenzyl and p-methoxyphenyl groups, cyclization involving a carbene insertion reaction, and conversion of the ketone moiety of the bicyclic compound (13b) into an enethiol moiety via enolphosphate activation. The target compound, the sodium salt (14c) did not possess any useful biological activity.