Asymmetric Syntheses of β-Amino Acids by the Reduction of Enamines

Abstract

Asymmetric synthesis of β-amino acids (4) was achieved by the reduction of chiral enamines (3) with 10% palladium hydroxide catalyst on charcoal or with sodium cyanoborohydride in optical purities of 3-28%. The reduction with the former catalyst afforded higher optical purities of 4 than that with the latter reducing agent. These two methods yielded opposite configurations of 4. The steric courses of the reactions are discussed.