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

The herein described studies on the enolization and subsequent alkylat ion 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 obtenti on of alpha-amino acids either of the L- or the D-series without the n eed of changing the chiral inducer: deprotonation with LDA or (t)BuLi followed by reaction with alkyl triflates gives rise to the 2R alpha-a mino acids, whereas the 2S isomers can be obtained by deprotonation wi th KO(t)Bu followed by reaction with alkyl halides.