Patent ID: 7390909

Claim:
A process of producing an optically active monatin represented by the following formula (8) or a salt thereof: wherein each * denotes, independently, an asymmetric center in the R- or S-configuration, wherein the reaction temperature of the process is set within a range of about 0 to 60° C., comprising: (a) reacting a glutaric acid compound represented by the formula (9) wherein R 2 represents a hydrogen atom or a group selected from the group consisting of alkyl groups, aryl groups, and aralkyl groups, and the bond marked with wavey line denotes that carbon atom to which it is attached may be in the R-configuration or the S-configuration, with an optically active amine represented by the formula (10): wherein R 3 , R 4 , R 5 , R 6 and R 7 , independently, represent a hydrogen atom or an alkyl group with one to 3 carbon atoms; * denotes an asymmetric center in the R-configuration or S-configuration, to form a diastereomer salt, and separating the diastereomer salt by crystallization, to obtain an optically active glutaric acid compound salt represented by the formula (11): wherein R 2 represents a hydrogen atom or a group selected from the group consisting of alkyl groups, aryl groups, and aralkyl groups, and R 3 , R 4 , R 5 , R 6 , R 7 , and * are as defined above; (b) dissociating the optically active glutaric acid compound salt represented by the formula (11) or exchanging the optically active glutaric acid compound salt with a different salt, to prepare an optically active glutaric acid compound represented by the formula (12) or a salt thereof (excluding the optically active glutaric acid compound salt represented by the formula (11)): wherein R 2 and * are as defined above, and converting the alkoxyimino group or hydroxyimino group of the optically active glutaric acid compound represented by the formula (12) to an amino group, to produce a monatin represented by the formula (13) or a salt thereof: wherein * and the bond marked with the wavy line are as defined above; and (c) crystallizing the monatin represented by the formula (13) or a salt thereof using a mixed solvent of water and an alcohol to obtain the optically active monatin represented by the formula (8).