DIASTEREOSELECTIVE SYNTHESIS OF SUBSTITUTED GLUTAMIC-ACID DERIVATIVES VIA MICHAEL ADDITIONS OF N-[BIS(METHYLTHIO)METHYLENE]GLYCINATES UNDER SOLID-LIQUID PHASE-TRANSFER CATALYSIS

Michael additions of the enolates of ethyl and tert-butyl N-[bis(methylthio)methylene]glycinates with alpha,beta-unsaturated esters and ketones under solid-liquid phase transfer catalysis allowed for the highly diastereoselective synthesis of substituted glutamic acid derivatives through a transition state chelation-controlled by the catalyst with a like approach of reactants. Selective removal of the iminodithiocarbonate protecting group with concomitant cyclization gave rise to 3-substituted pyroglutamates and 1,3,4-trisubstitued Delta(1)-pyrrolines with retention of configuration.