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

Chiral cis and trans glycidic esters 9 substituted by alkyl or ethoxycarbon yl react with cysteamine or o-amino-thiophenol 10 by stereoselective ring t ransformation to non-aromatic optically active 2-(alpha-hydroxyalkyl)-1,4-t hiazin-3-ones 12. The attack of the mercapto function at the alpha-position of the glycidate occur's predominantly by inversion of configuration. As c ompared with known reactions of aryl-substituted glycidates with o-aminothi ophenol or cysteamine preferentially giving thiazepinones, a remarkable eff ect of the substituent in the glycidate on the regiochemistry was found.