A simple and efficient strategy for the regio- and stereoselective synthesis of carbon-branched sugar derivatives is described. The successful implementation of Wittig rearrangement on substrates derived by Ferrier rearrangement of various glycals and 3--alkenyl glycals is studied extensively. A highly selective [1,2]- or [2,3]-Wittig rearrangement is revealed that provides a novel class of stereodefined 3--branched glycals and -glycosides, which are otherwise difficult to obtain.
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