One-Step, Stereocontrolled Synthesis of Glycosyl 1-Phosphates, Uridine-5‘-diphosphogalactose, and Uridine-5‘-diphosphoglucose from Unprotected Glycosyl Donors

The reaction of 2-(1,2- trans -glycopyranosyloxy)-3-methoxypyridines (MOP glycosides) with phosphoric acid leads to the corresponding 1,2- cis -1-phosphates in good yield and excellent stereoselectivity. 1-Phosphate esters of α- d -glucopyranose, α- d -galactopyranose, and 2-azido-2-deoxy-α- d -galactopyranose were thus prepared without recourse to protective groups. In the l -fucose series, the major product was the α- l -fucosyl 1-phosphate. An alternative method that relies on neighboring group participation allowed the preparation of a protected β- l -fucosyl 1-phosphate. Reaction of unprotected β- d -glucopyranosyloxy and β- d -galactopyranosyloxy MOP donors with uridine diphosphoric acid gave UDP-Glc and UDP-Gal with preponderance of the desired α-anomeric configuration.