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 alpha-D-glucopyranose, alpha-D-galactopyranose, and 2-azido-2-deoxy-alpha-D-galactopyranose were thus prepared without recourse to protective groups. In the L-fucose series, the major product was the alpha-L-fucosyl I-phosphate. An alternative method that relies on neighboring group participation allowed the preparation of a protected beta-L-fucosyl I-phosphate. Reaction of unprotected beta-D-glucopyranosyloxy and beta-D-galactopyranosyloxy MOP donors with uridine diphosphoric acid gave UDP-Glc and UDP-Gal with preponderance of the desired alpha-anomeric configuration.