PROCESSES FOR THE PRODUCTION OF OPTICALLY ACTIVE COMPOUNDS HAVING SUBSTITUENTS AT THE 2-POSITION

The present invention provides a process for producing an optically active compound having a thio group at the 2-position important for manufacturing medicines. An optically active compound having a hydroxyl group at the 2-position is chlorinated with inversion of the configuration at the 2-position, and the resultant optically active compound having a chlorine atom at the 2-position is reacted with a metal thiolate to introduce a thio group with inversion of the configuration at the 2-position. This process is capable of minimizing racemization and producing an optically active compound having a thio group at the 2-position at low cost in high yield. When the optically active compound having a chlorine atom at the 2-position is reacted with the metal thiolate in coexistence with water in the reaction system, the optically active compound having a thio group at the 2-position with higher optical purity can be produced in higher yield. An optically active carboxylic acid having a thio group at the 2-position is crystallized in the presence of an aliphatic hydrocarbon solvent and/or a sulfur-containing solvent to effectively remove coexistent impurities such as an optical isomer and the like, thereby producing crystals of an optically active carboxylic acid having a thio group at the 2-position with higher purity.