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