Synthesis of optically active 3,4,5,6-tetrahydro-2H-1,4-thiazin-3-ones and their benzo analogues by ring transformation of glycidic esters

Abstract

Chiral cis and trans glycidic esters 9 substituted by alkyl or ethoxycarbonyl react with cysteamine or o-aminothiophenol 10 by stereoselective ring transformation to non-aromatic optically active 2-(α-hydroxyalkyl)-1,4-thiazin-3-ones 12. The attack of the mercapto function at the α-position of the glycidate occurs predominantly by inversion of configuration. As compared with known reactions of aryl-substituted glycidates with o-aminothiophenol or cysteamine preferentially giving thiazepinones, a remarkable effect of the substituent in the glycidate on the regiochemistry was found.