ASYMMETRIC ALKYLATION OF 8-PHENYLMENTHYL N-[BIS(METHYLTHIO)METHYLENE]GLYCINATE ENOLATES - SYNTHESIS OF D- AND L-ALPHA-AMINO ACIDS FROM A SINGLE CHIRAL PRECURSOR

摘要

The herein described studies on the enolization and subsequent alkylation of the acyclic glycine title ester evidence the involvement of the kinetics of the alkylation step on the stereochemical outcome of the overall process, apart from that of the deprotonation sequence itself. Careful choice of reaction conditions allow for the selective obtention of alpha-amino acids either of the L- or the D-series without the need of changing the chiral inducer: deprotonation with LDA or (t)BuLi followed by reaction with alkyl triflates gives rise to the 2R alpha-amino acids, whereas the 2S isomers can be obtained by deprotonation with KO(t)Bu followed by reaction with alkyl halides.