Superbase-Catalyzed Stereo- and Regioselective Glycosylation with 2‑Nitroglycals: Facile Access to 2‑Amino-2-deoxy‑O‑glycosides

An efficient superbase-catalyzed stereo- and regioselective glycosylation of 2-nitroglycals with high functional group compatibility is reported. The ion pair generated from alcohol and a catalytic amount of P4-t-Bu was vital for the successful implementation of this stereoselective glycosylation under mild conditions, producing moderate to good yields. Under reported reaction conditions, 2-nitrogalactals produce α-stereoisomers exclusively, while 2-nitroglucal yielded more β-products. The notable difference between the outcomes was investigated by the density functional theory (DFT) study. In addition, we have synthesized the key intermediate of a mucin-type core-6 glycoconjugate, thus illustrating the synthetic potency of this method.