Enantioselective Oxidation of Beta-hydroxythioethers .1. Synthesis of Optically-active Alcohols and Epoxides

Optically pure beta-dydroxysulfoxides may be obtained by direct oxidation of the parent thioethers with the modified Sharpless reagent developed in our laboratory. Necessary requisites for a succesful asymmetric oxidation are both the protection of the OH function and the largest possible difference in size of the two groups linked to the thioether sulfur. This latter condition is fulfilled by using S-methyl derivatives. Examples referring to the oxidation of various S-methyl-beta-dydroxythioethers, characterized by e.e. values up to 80%, which may be further increased (> 98%) by crystallization, are presented. Results concerning the synthesis of optically active epoxides and alcohols starting from beta-hydroxysulfoxides are also presented which, in some cases, allows the absolute configuration of the parent sulfoxide to be established.