SYNTHESIS OF UNSYMMETRICAL TREHALOSE ANALOGS BY SILVER TRIFLUOROMETHANESULFONATE PROMOTED GLYCOSYLATIONS

The coupling of benzoylated glucosyl bromides with 2,3,4,6-tetra-O-benzylated gluco, manno or galacto-pyranoses promoted by silver triflate is described, and the compositions of the crude reaction mixtures, determined by C-13 NMR spectroscopy, are presented. Unsymmetrical trehalose derivatives can be synthesized by such couplings. However, the inherent formation of dimerization products of the reactants reduces the versatility of the reactions. The synthesis of alpha-D-glucopyranosyl alpha-L-glucopyranoside and alpha-D-glucopyranosyl beta-L-glucopyranoside is also described.