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

Abstract

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 [a] G. Merieux, M. Buchotte, M. Muzard, R. Plantier-Royon the corresponding exo-glycals in the furanose series. Recently, trifluoromethylated six-membered thioglycals were prepared via a multi-step synthetic sequence with a regioselective [4+2]cycloaddition between a fluorinated dithiocarboxylate and 1acetoxybutadiene in the first step. [18] As carbohydrate-derived sulfonium compounds are known to be an interesting class of glycosidase inhibitors, [19] we were also interested in the alkylation at the sulfur atom of the C-2 substituted thioglycals leading to 6-membered ring unsaturated sulfonium compounds. Scheme 7. Synthesis of 2-substituted thioglycals 15 and 16. Scheme 8. Preparation of sulfonium compound 18 and 18′ from thioglycal 16.