Synthesis of Ketodeoxysugars from Acylated Pyranosides Using Photoredox Catalysis and Hydrogen Atom Transfer

The combined action of a photoredox catalyst, a hydrogen atom transfer mediator, and a hydrogen bond acceptor cocatalyst has been used to achieve the transformation of pyranoside-derived esters into ketodeoxysugars. The position of the acyl group dictates the site of deoxygenation, enabling the preparation of 2-deoxy- and 4-deoxyketosugar derivatives. The products are useful precursors to rare sugar components of bioactive secondary metabolites. Computational studies are consistent with a radical lyaselike mechanism wherein the key elimination step proceeds via 1,2-acyloxy migration in the radical intermediate.