To efficiently obtain an optically active amino acid (derivative) in high optical purity by previously preparing an optically active amino acid (derivative) in an optical purity not lower than a convergent value of mutual solubility between optical isomers and crystallizing an optically active amino acid (derivative) which excessively exists.
One or more kinds of optically active amino acids (derivatives) selected from a group of phenylglycine (derivative), phenylalanine (derivative), homophenylalanine (derivative) and naphthylalanine (derivative) are previously prepared in an optical purity not lower than a convergent value of mutual solubility between optical isomers and an optically active amino acid (derivative) which excessively exists is crystallized to provide the objective optically active amino acid (derivative) having high optical purity. Furthermore, the convergent value of mutual solubility between optical isomers indicates a ratio (optical purity in mother liquid) of target optical isomer to optical isomers in mother liquid equilibrated when crystals of racemic substance and optically active substance simultaneously exist and the value is constant without depending on a ratio of crystals of the racemic substance and the optically active substance.
IRINO SHIGEAKI (JP)
TOKUDA AKIRA (NL)
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