Optical Resolution of DL-Proline by Forming a New Diastereoisomeric Solid Complex with L-Tartaric Acid

Abstract

DL-Proline was found to form new diastereoisomeric solid complexes with L-tartaric acid in a molar ratio of 1:1 from an aqueous ethanol. The complex of L-proline was less soluble than that of D-proline. On the basis of these properties, DL-proline was easily resolved by the usual chemical resolution technique without the necessity of converting to the derivative. The optically impure D-proline was racemized by heating at 170°C for 4 hr in water containing an equimolar amount of sodium hydroxide and was reused for resolution step.