Synthesis of 2‐Substituted Thioglycals from Carbohydrate‐Derived Ketene Dithioacetals.

A novel strategy for the synthesis of 2‐substituted thioglycals has been developed from a carbohydrate‐derived ketene dithioacetal in a two‐step sequence. The introduction of various electrophilic groups at the double bond of the ketene dithioacetal was achieved before the elimination of the thioalkyl group to yield 2‐substituted thioglycals. Removal of the exocyclic thioalkyl group was obtained by the selective formation of the exocyclic glycosyl sulfoxide followed by treatment by an organolithium reagent. The synthetic potential of these 2‐substituted thioglycals was illustrated by the alkylation at the sulfur atom leading to unsaturated carbohydrate‐derived sulfonium salts. [ABSTRACT FROM AUTHOR]