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.