β-Lactams from Ester Enolates and Silylimines: Enantioselective Synthesis of the trans-Carbapenem Antibiotics (+)-PS-5 and (+)-PS-6

Article abstract of DOI:10.1021/jo00021a007

A new synthetic route to the antibiotics (+)-PS-5 and (+)-PS-6 is described.The preparation involves a fully stereocontrolled reaction between the enantiomerically pure N-trimethylsilylimine of lactic or mandelic aldehyde and the lithium enolate of the tert-butyl butanoate or tert-butyl isovalerate, respectively.Conversion of the azetidinones obtained to 4-acetoxy derivatives via oxidative cleavage of the hydroxyethyl or hydroxybenzyl side chain and introduction of the necessary appendage in the position 4 of the azetidinone ring, followed by assemlage of the bicyclic ring system, afforded the natural trans-carbapenems (+)-PS-5 and (+)-PS-6.