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 employing as key-step the cycloaddition reaction of N-trimethylsilylimine of O-protected lactic aldehyde (4) and cyclic silyl derivative of glycine (2). The elaboration of hydroxyethyl side chain was carried out by functional group interchange (FGI) of the hydroxyl group by a thioacetoxy group, and finally six-membered ring assembly followed by attachment of necessary appendage to N-7 nitrogen atom.