Synthesis of methylene bridged C-disaccharides

Addition of glycosyl radicals to the α-methylene lactones 8 obtained from the corresponding glycopyranosyl phenylsulfoxides 5a,b in convenient two step procedures provides methylene bridged C-disaccharides in high diastereoselectivities. Thus, after reduction of the lactone moiety the methylene bridged analogs 9–11 of kojibiose, ristobiose, and α-L-fucopyranosyl (1→2)-D-galactose, respectively, were obtained.