InCl3-catalyzed rapid 1,3-alkoxy migration in glycal ethers:: Stereoselective synthesis of unsaturated α-O-glycosides and an α,α-(1→1)-linked disaccharide

InCl3 catalyzes a facile stereoselective 1,3-migration of allylic ethers of glycals to afford 2-C-methylene- and 2,3-unsaturated-alpha-O-glycosides in high yields. The reaction is rapid (10 min), requires only 20 mol-% of the catalyst, and is compatible with acid-labile functional groups such as epoxides and acetals. This methodology provides a convenient alternative to the Ferrier rearrangement. A direct synthesis of an alpha,alpha-(1 -> 1)-linked disaccharide derivative by a domino process is also reported. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).