Stereocontrolled synthesis of beta-lactams via Staudinger reaction betweenphenoxyketenes and chiral imines

Chiral Schiff bases derived from esters of valine and alanine have been sho wn to be useful intermediates for the stereoselective synthesis of beta -la ctams. Staudinger reaction between these compounds and phenoxyketenes, gene rated in situ, from the corresponding acid chlorides in the presence of tri ethylamine, provides a mixture of diastereomeric cis-beta -lactams. Attempt s have been made to separate them using column chromatography and their rat ios determined through H-1 NMR data.