Editing Sugars: Decatungstate Photocatalyzed Site- and Stereoselective C-H Functionalization in ß-Fucosides

C–H bond functionalization via (photoinduced) Hydrogen Atom Transfer (HAT) catalysis is emerging as a powerful eco-sustainable tool for sugar editing, albeit challenges in governing the reactivity patterns and site-selectivity remain. Quite surprisingly, no functionalization of the C-5 position in pyranoses via C–H activation has been described to date. We herein report the development of an efficient methodology for the site-selective and stereoselective alkylation of position 5 of β-fucosides by means of decatungstate photocatalyzed C(sp3)–C(sp3) bond formation. The experimental work is accompanied by spectroscopical studies based on laser flash photolysis and supplemented by computational simulations, offering insights into the reasons underlying the selectivity profile of the reported transformations.