Preparation of optically active alpha-methyl-beta- mercaptopropionic acid derivative

PURPOSE: To prepare the titled compound extremely useful as an intermediate of pharmaceuticals, economically, in high efficiency, by treating a DL-α-methyl-β- mercaptopropionic acid derivative with a specific amine-type resolving agent. CONSTITUTION: 1mol of a DL-α-methyl-β-mercaptopropionic acid derivative of formula I [R 1 is acetyl or (substituted) benzoyl] is mixed with ≤1mol of an optically active (R or S) aminoalcohol of formula II (R 2 is methyl, etc.) to produce a diastereomer salt, which is then separated into D and L optical isomers taking advantage of the solubility difference. Each salt is acidified with an aqueous solution of a mineral acid to obtain the titled compound of formula III. EFFECT: An economical method for the preparation of N-(D-α-methyl-β-mercaptopropionyl)-L-proline extremely useful as a hypotensor. COPYRIGHT: (C)1981,JPO&Japio