Method for producing optically active amino acid or derivative thereof having high optical purity

摘要

A method for producing an optically active amino acid or derivative thereof having a high optical purity from an optically active amino acid comprising optical isomers or derivative thereof, which comprises any one of processes (A), (B), and (C), wherein the process (A) comprises the steps: (1) previously preparing an optically active amino acid or derivative thereof having an optical purity higher than a convergent value of a mutual solubility of the optical isomers and (2) crystallizing the optically active amino acid or the derivative thereof that exists in excess, said convergent value being a ratio of the desired optical isomer in the optical isomers dissolved in a mother liquor in which crystals of a racemate and an optically active compound coexist at equilibrium (the optical purity in a mother liquor). The processes (B) and (C) are described in the specification.