Optical resolution of racemic alanine - via racemic alanine maleate

摘要

Process for the optical resolution of DL-alanine, wherein DL-alanine is reacted with an equimolar amt. of maleic acid and the resulting DL-alanine maleate subjected to crystallization, wherein a suitable amount of the optically active crystals are added as seed to precipitate the objective crystals of high optical purity. DL-Alanine (62.4 g) and maleic acid (81.1 g) are dissolved in water (70 ml). While the soln. is kept at 49 degrees C, L-alanine maleate (10 g) having a crystal size of not less than 24 mesh is added, and the mixture cooled at a rate of 1 degree C/10 mins. After 20 mins., finely powdered D-alanine maleate (2 g) is added and the mixture further cooled to 30 degrees C. After 1 hr., the crystals are collected and passed through a 48-mesh sieve to give L-alanine maleate (32.3 g., 81.8% purity) and D-alanine maleate (20.6 g, 76.7% purity).