| abstract |
A practical process for easily or industrially advantageously producing from an easily available inexpensive material an optically active α-substituted cysteine or salt thereof useful as an intermediate for medicines, etc. The process, which is for producing an optically active α-substituted cysteine or salt thereof, comprises converting a cysteine derivative into a thiazoline compound, subjecting the compound to a stereoselective substituent-introducing reaction with the aid of an optically active quaternary ammonium salt, especially an axially asymmetric quaternary ammonium salt, as a catalyst to thereby obtain an optically active thiazoline compound, and hydrolyzing it. |