Synthesis of Optically Active 1,4-Thiazane-3-carboxylic Acid via Optical Resolution by Preferential Crystallization of (RS)2-Amino-3-[(2-chloroethyl)sulfanyl]propanoic Acid Hydrochloride

Article abstract of DOI:10.1271/bbb.62.2382

Optically active 1,4-thiazane-3-carboxylic acid [TCA] was synthesized from cysteine via optical resolution by preferential crystallization. The intermediate (RS)-2-amino-3-[(2-chloroethyl)sulfanyl]propanoic acid hydrochloride [(RS)-ACS-HCl] was found to exist as a conglomerate based on its melting point, solubility and IR spectrum. (RS)-ACS·HCl was optically resolved by preferential crystallization to yield (R)- and (S)-ACS·HCl. (R)- and (S)-ACS·HCl thus obtained were recrystallized from a mixture of hydrochloric acid and 2-propanol, taking account of the solubility of (RS)-ACS·HCl, efficiently yielding both enantiomers in optically pure forms. (R)- and (S)-TCA were then respectively synthesized by the cyclization of (R)- and (S)-ACS·HCI in ethanol in the presence of triethylamine.