Dual-Participation Protecting Group Solves the Anomeric Stereocontrol Problems in Glycosylation Reactions

The 2,2-dimethyl-2-(ortho-nitrophenyl)acetyl (DMNPA) group permits, via robust neighboring group participation (NGP) or long distance participation (LDP) effects, the stereocontrolled 1,2-trans, 1,2-cis, as well as beta-2,6-dideoxy glycosidic bond generation, while suppressing the undesired orthoester byproduct formation. The robust stereocontrol capability of the DMNPA is due to the dual-participation effect from both the ester functionality and the nitro group, verified by control reactions and DFT calculations and further corroborated by X-ray spectroscopy.