BETA-LACTAMS FROM ESTER ENOLATES AND N-TMSIMINES - ENANTIOSELECTIVE SYNTHESIS OF (6R,7S)-1-BETA-3-DIMETHYL-3-ISOCEPHEM

Enantioselective synthesis of active isocephem 1 was accomplished empl oying as key-step the cycloaddition reaction of N-trimethylsilylimine of O-protected lactic aldehyde (4) and cyclic silyl derivative of glyc ine (2). The elaboration of hydroxyethyl side chain was carried out by functional group interchange (FGI) of the hydroxyl group by a thioace toxy group, and finally six-membered ring assembly followed by attachm ent of necessary appendage to N-7 nitrogen atom.