Indium-mediated alkynylation of sugars: synthesis of C-glycosyl compounds bearing a protected amino alcohol moiety.

The coupling of glycals with an alkynyl iodide bearing a protected amino alcohol moiety was achieved in the presence of metallic indium under Barbier conditions. It gave functionalized C-glycosyl compounds, precursors of C-glycosyl amino acids with α configuration.

Ferrier-type alkynylation reaction mediated by indium.

An efficient Ferrier-type alkynylation reaction between glycals and iodoalkynes using Barbier conditions is described. These conditions require In0, InI, or InII and lead to alpha-2,3-unsaturated-C-glycosides with good stereoselectivity. When glycosyliodoalkynes are used, trehalose-derived compounds and alpha-(1-->6)-C-disaccharides are obtained.

A highly selective route to beta-C-glycosides via nonselective samarium iodide induced coupling reactions.

Stereoselective preparation of beta-C-glycosides has been developed from acetylated glycopyranosyl 2-pyridyl sulfones, involving a samarium-Barbier coupling procedureoxidation-isomerization sequence.