New O-Glycosidation Methods for the Synthesis of Unnatural Oligosaccharides” XLII

an efficient de novo route enabling all eight L-hexoses synthesis has been developed by Guaragna et al. [3,4] based on the synthesis of the key intermediates 3 and 4 starting from the homologating agent 1. Based on capability of these sulfur-containing moieties to activate neighboring acetal functions, [5] as proved by the equilibrium existing between 3 and 4 (FIGURE 2), [6] their unprecedented activation, respectively at C1 and C4 positions, has been herein exploited to make them glycosyl donors into O-glycosidation reactions for the synthesis of di- and oligosaccharides structures containing enantiopure L-hexoses under extremely mild acidic conditions and without the need to install leaving group at the anomeric positions.