Synthesis of Disaccharide Nucleosides Utilizing the Temporary Protection of the 2′,3′-cis-Diol of Ribonucleosides by a Boronic Ester

Disaccharide nucleosides are an important class of natural compounds that have a variety of biological activities. In this study, we report on the synthesis of disaccharide nucleosides utilizing the temporary protection of the 2′,3′-cis-diol of ribonucleosides, such as adenosine, guanosine, uridine, 5-metyluridine, 5-fluorouridine and cytidine, by a boronic ester. The temporary protection of the above ribonucleosides permits the regioselective O-glycosylation of the 5’-hydroxyl group with thioglycosides using a p-toluenesulfenyl chloride (p-TolSCl)/silver triflate (AgOTf) promoter system to afford the corresponding disaccharide nucleosides in fairly good chemical yields. The formation of a boronic ester prepared from uridine and 4-(trifluoromethyl)phenylboronic acid was examined by (1)H, (11)B and (19)F NMR spectroscopy.