Kinetics of chiral resolution in stirred crystallization of D/L-glutamic acid

Stirred crystallization of racemic (D/L)-glutamic acid (Glu) in the presenc e of small amounts of L- or D-lysine (Lys) was studied for the effect of tr ansient chiral resolution by monitoring the time evolution of optical rotat ion and the concentration of the solution, The presence of a small amount o f L- or D-Lys retards the crystallization rate of the corresponding enantio mer of Glu in a chirally selective manner, giving rise to transient optical resolution of racemic Glu during crystallization. The optical rotation of the Glu solution was found to increase from zero to a value corresponding t o an enantiomeric excess tee) of 22-35% and subsequently decreases to zero over a period of many hours. During this process, the ee of the crystallize d Gu is nearly 100% during the first 35 min and then it decreases slowly to zero. Our results indicate that the time at which the ee of the solution r eaches its maximum and the maximum value of the ee show a nonlinear depende nce on the initial mole fraction of the chiral impurity. The effect of the impurity is highly chirally selective, indicating "molecular recognition." Chirality 11: 343-348, 1999. (C) 1999 Wiley-Liss, Inc.