[1,2]-Wittig rearrangement of acetal systems: A highly stereocontrolled conversion of O-glycosides to C-glycosides

We envisioned that acetal systems such as O-glycosides would undergo the [1,2]-Wittig shift with great facility owing to the relatively large stability of the α-oxy radical, together with retention of the anomeric configuration. We now wish to report that the [1,2]-Wittig rearrangement of O-glycosides proceeds with efficient stereocontrol over both the anomeric center and the new chiral center formed on the side chain to give the stereo-defined C-glycosides in high yields. We have demonstrated that the [1,2]-Wittig rearrangement of O-glycosides proceeds with efficient stereocontrol over both the anomeric center and the side-chain chiral center to give a novel class of the stereo-defined C-glycosides which is otherwise difficult to obtain.