Preferential Crystallization of D, L-Pyridyl Alanine by Diastereoisomer Method

Since pyridyl alanine (PA) synthesized as an intermediate of medicine is racemic, the mixture requires optical separation. A novel method of optical separation comprising the formation of diastereoisomer salt by L-tartaric acid and preferential fractional crystallization was found, and the optical purity of L-PA crystals obtained was more than 96 %. Furthermore, it was clarified that the crystallization of D-PA, which is useless for medicine, is depressed by addition of NaOH to the crystallization solution. Finally, by using the Z-factor proposed by us as a key factor in crystallizer scale-up, the optimum design for industrial crystallization was developed.