Synthesis of Non-anomeric Spiro-Fused Bicyclic Sugar Derivatives by Light-Mediated 1,5-Hydrogen Atom Transfer (HAT) Process

We report a metal-free, diastereoselective approach for the syntheses of conformationally locked spiro bicyclic sugars bearing a quaternary center at C5 position. The oxazoline-containing spiro-bicyclic system has been built in one step from easily synthesizable C6-glycosylimidates under visible light conditions. The overall transformation proceeds with the formation of an intramolecular C-N bond through the activation of appropriately positioned C-H bond via in situ generation of an imidate nitrogen radical followed by an intramolecular 1,5-hydrogen atom transfer (HAT) in the presence of NaI/PIDA reagents. Mild reaction conditions, green source of energy, broad substrate scope, scale-up synthesis, and high reaction yields are some of the key features of the developed protocol.