Stereochemical Study on α-Alkylation of β-Branched α-Amino Acid Derivatives via Memory of Chirality

Abstract

α-Alkylation of N-Boc-N-MOM amino acid derivatives with an additional chiral center at the β-carbon proceeded with retention of configuration, irrespective of the chirality at the β-carbon. The C-N axial chirality of the enolate intermediates played a decisive role in the stereochemical course of the alkylation, while the central chirality of the β-carbon had little effect. Amino acid derivatives with contiguous quaternary and tertiary stereocenters are readily obtained in a stereochemically expectable manner.