Synthesis of optically active α-methylene β-lactams through lipase-catalyzed kinetic resolution

A convenient method for the preparation of the hitherto unknown chiral alpha-methylene beta-lactam derivatives 5a,b is reported. The optically active alpha-methylene beta-lactams 5a-c, and their corresponding amino acids 6a-c have been readily made available through lipase-catalyzed kinetic resolution in high enantiomeric purity (up to 99% ee). The N-substituted beta-lactam derivatives 4a,b and 10 are not accepted by the lipases and were prepared in optically active form by chemical transformation.