Sugar Acetylene for New Stereocontrolled Synthesis.

Abstract

A review with >20 refs. Reactions of silylacetylenes with glycals give sugar acetylenes by the selective introduction of acetylenic groups to sugar rings. Bis-C-glycosidation allows introduction of 2 sugars at both ends of a bis(trimethylsilyl)acetylene. A 2,3-dideoxyglucose deriv. provided the corresponding C-1 alpha acetylenic compds., which would increase the scope of C-glycosidation with silylacetylenes. An alkynyl group attached to the anomeric position of a pyranose ring was epimerized through a dicobalthexacarbonyl complex by treatment with trifluoromethanesulfonic acid. The epimerization reaction led to provide either alpha or beta alkynyl C-glycoside as desired. Ring opening of a dihydropyran deriv. using Nicholas-type cation intermediates was also accomplished. Applications of the reactions to syntheses of okadaic acid, tautomycin, and ciguatoxin are also described.