STEREOCHEMICALLY CONTROLLED DECOMPOSITION OF SILVER-CATIONIZED METHYL GLYCOSIDES

Silver ion adducts of several methyl glycopyranosides were generated by fast atom bombardment of 1 : 1 mixtures of the glycosides with silver nitrate. The unimolecular decompositions of [M + Ag]+ ions showed dramatic differences related to the relative positions of both the hydroxyl group on C(2) and the anomeric methoxyl group. When these groups were in the cis position, methanol was exclusively expelled. When they were in the trans position, silver hydride was preferentially lost. The stereoselective elimination reaction is proposed to proceed through a five-membered silver-containing intermediate complex. from the oxygen on C(2) to the anomeric substituent (methoxyl group or hydrogen atom).