The intermolecular C–O coupling reaction of 1,4-quinones with exo-glycals under iron hydride hydrogen atom transfer (HAT) conditions is described. This method provides a direct and regioselective access to a wide range of phenolic O-ketosides related to biologically relevant natural products in diastereomeric ratios up to >98:2 in the furanose and pyranose series. No trace of the corresponding C-glycosylated products that might have resulted from the radical alkylation of 1,4-quinones was observed. The results of mechanistic experiments suggest that the key C–O bond-forming event proceeds through an oxidative radical–polar crossover process involving a single-electron transfer between the HAT-generated glycosyl radical and the electron-acceptor quinone.

We describe herein a convenient access to glycosyl cyanides by way of TMSCN ring opening of 1,6-anhydro sugars mediated by TMSOTf with modest to high stereocontrol in the D-gluco, Dgalacto and D-manno series. The reaction is tolerant to various functional groups including free alcohols, alkenes and terminal alkynes. The straightforward synthesis of a constrained analogue of 1-cyano-D-glucal with a 3,6-anhydro sugar framework is presented to illustrate the interest of the TMSCN ring-opening reaction.