Photolabile Protecting Group-Mediated Synthesis of 2-Deoxy-Glycosides

A green and efficient photolabile protecting group (PPG)-mediated glycosidation approach for the synthesis of 2-deoxy-glycosides is reported. By employing ortho-nitrobenzyl carbonate (oNBC) as PPG, N,N-dimethylformamide (DMF)-modulated SPhosAuNTf₂-promoted glycosidation with per-oNBC-protected 2-deoxy-glycosyl ynenoates affords the 2-deoxy-glycosides with moderate to excellent α-selectivities presumably depending on the reactivities of the acceptor alcohols. Based on the PPG-mediated glycosidation approach, oligosaccharides with three to six oNBC groups are effectively achieved. The multiple oNBC groups in the 2-deoxy-glycosides are completely cleaved by irradiation at 365 nm, resulting in the desired 2-deoxy-glycosides in an efficient manner without affecting the common alkyne, alkene, azide functional groups and the traditional protecting groups on the aglycones.