HFIP-Promoted Stereoselective Sulfenylative <i>O</i> -Glycosylation of Glycals

The highly stereoselective sulfenylative <i>O</i>-glycosylation of glycals, enabled by hexafluoroisopropyl alcohol (HFIP), has been successfully developed for the first time. This methodology is compatible with three types of oxygen nucleophiles, including alkyl alcohols, phenols, and water. Glycal derivatives such as D-galactal, D-arabinal, L-fucal, and d-glucal are suitable substrates for this reaction system. A range of 2-phenylthio-<i>O</i>-glycosides were obtained in moderate to excellent yields with excellent β-selectivity (β:α > 20:1), including those bearing disaccharide structures. The thioether group at the C-2 position of the glycosides can be readily removed to afford the corresponding 2-deoxy-β-glycosides, which were efficiently synthesized in good yields.