Imidazolidinone derivative, method of producing the same and method of producing optically active amino acid

The objective of the present invention is to provide an optically active imidazolidinone derivative widely usable for synthesizing an optically active amino acid, a method of easily producing the derivative, and a method of easily producing an optically active amino acid by using the derivative. The objective can be achieved by producing an optically active amino acid using a novel optically active imidazolidinone derivative represented by a general formula (3) and the like. According to the method of the present invention, an optically active imidazolidinone derivative can be obtained by preferential crystallization from a mixture of isomers of the imidazolidinone derivative. Therefore, an optically active amino acid can be easily and stereoselectively produced without cumbersome procedures required for the conventional methods, such as resolution of diastereomers, synthesis from an optically active amino acid and resolution of isomers by silica gel column chromatography.