Asymmetric synthesis of (2S,3S)- and (2R,3R)-α,β-dialkyl-α-amino acids via alkylation of chiral nickel(II) complexes of aliphatic α-amino acids with racemic α-alkylbenzyl bromides

This study has demonstrated that the stereochemical outcome of the direct alkylation of nickel(II) complexes derived from chiral Schiff bases of glycine, alanine, 2-aminobutyric acid, and leucine with racemic alpha-methylbenzyl bromide depends on the steric bulk of the corresponding amino acid residue. In particular, the alkylation of the alanine complex was found to proceed with a synthetically useful level (90% de) of stereoselectivity offering a concise synthesis of enantiomerically pure (2S,3S)- or (2R,3R)-alpha,beta-dimethylphenylalanines.