Optical Resolution by Preferential Crystallization of (RS)-2-Amino-3-(2-carboxyethylthio)propanoic Acid.

Electrophilic additions of DL- and L-Cys to propenoic acid afforded (RS)- and (R)-2-amino-3-(2-carboxyethylthio)propanoic acids [(RS)- and (R)-ACE], respectively. (RS)-ACE was found to exist as a conglomerate based on its melting point, solubility, and infrared spectrum. (RS)-ACE was optically resolved by preferential crystallization to yield (R)- and (S)-ACE. The obtained (R)- and (S)-ACE were efficiently recrystallized from water, taking account of the solubility of (RS)-ACE, to give them in optically pure form.