introduced for the control of enantioselectivity of alkylation of phenylalanine derivatives by regulation of the aggregate structure of chiral enolate intermediates. Use of amino acid-dimers, 6 and 15, was effective to minimize solvent- and electrophile-dependency of enantioselectivity of the alkylation. α-Allylation of 20 proceeded in improved selectivity of 82–88% ee under the control of aggregation
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 P-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