Provided is a method for separating the four optical isomers of Nahlsgen. The method according to the present invention for producing a mixture of a D-2-amino-4-[(Rp)-(3-carboxymethylphenoxy)(methoxy)phosphoryl]butanoic acid hydrate and an L-2-amino-4-[(Sp)-(3-carboxymethylphenoxy)(methoxy)phosphoryl]butanoic acid hydrate includes subjecting a mixture of the four optical isomers, represented by Formula (1′), to fractional crystallization from water or from a solvent mixture of water and a water-soluble organic solvent, to precipitate a mixture of a compound represented by Formula (1-1′-1) and a compound represented by Formula (1-4′-1), where Formulae (1′), (1-1′-1), and (1-4′-1) are expressed as follows:
本发明提供了一种分离 Nahlsgen 四种光学异构体的方法。根据本发明,生产 D-2-
氨基-4-[(Rp)-(3-羧甲基苯氧基)(甲氧基)
磷酰]
丁酸水合物和
L-2-
氨基-4-[(Sp)-(3-羧甲基苯氧基)(甲氧基)
磷酰]
丁酸水合物混合物的方法包括将式(1′)表示的四种光学异构体的混合物、从
水中或从
水和
水溶性有机溶剂的混合溶剂中进行分馏结晶,析出由式(1-1′-1)表示的化合物和由式(1-4′-1)表示的化合物的混合物,其中式(1′)、(1-1′-1)和(1-4′-1)表示如下: