Stereoselective synthesis of BRL 56173, a bicyclic acrylic penicillin highly stable to beta-lactamases.

stability to /Mactamases (evinced by lower MICs against /Mactamase producing strains of Haemophilus and Staphylococcus) compared to 1. However, 2 was produced as a mixture of stereoisomers which were not easily separated and was therefore not promising for further study. Following the theme of 2-substitution, we subsequently discovered a series of bicyclic acrylic penicillins3) of which the most interesting was 3, BRL 56173, which could be obtained more readily as the desired single