Boronic Acid-Catalyzed Regio- and Stereoselective -Glycosylations of Purines and Other Azole Heterocycles: Access to Nucleoside Analogues.

In the presence of an arylboronic acid catalyst, azole-type heterocycles, including purines, tetrazoles, triazoles, indazoles, and benzo-fused congeners, undergo regio- and stereoselective -glycosylations with furanosyl and pyranosyl trichloroacetimidate donors. The protocol, which does not require stoichiometric activators, specialized leaving groups, or drying agents, provides access to nucleoside analogues and enables late-stage -glycosylation of azole-containing pharmaceutical agents. A mechanism involving simultaneous activation of the glycosyl donor and acceptor by the organoboron catalyst has been proposed, supported by kinetic analysis and computational modeling.