Chiral Auxiliary for the Synthesis of Optically Active Amino Acids
(S)-N-(2-Benzoylphenyl)-1-benzylpyrrolidine-2-carboxamide (1) is a chiral auxiliary agent used in the synthesis of optically active amino acids. When racemic α-amino acids as substrates react with 1 in presence of nickel nitrate and sodium methoxide, the isomerization at the α-position of the amino acids occurs via the formation of an intermediate 2. The hydrolysis of 2 by acid yields (S)-amino acids with high optical purity.1) When the nickel complex of 1 and glycine is treated with 3, the introduction of an alkyl group proceeds to give 4. Subsequent hydrolysis and protection with Fmoc-OSu affords Nα-Fmoc-ω-alkynyl-L-amino acids.2)
