A Pd-catalyzed approach to (1-->6)-linked C-glycosides.

A flexible and robust method for the assembly of (1-->6)-linked C-glycosidic disaccharides is presented. The key reaction is a Pd-catalyzed coupling of 1-iodo- or 1-triflato-glycals with alkynyl glycosides. Reinstallation of the native hydroxyl group pattern is achieved after selective hydrogenation of the triple bond using Raney-nickel. Epoxidation with DMDO and reductive epoxide opening gives access to either the alpha- or the beta-derivative, depending on the hydride source.