Glycosyl dithiocarbamates: β-selective couplings without auxiliary groups.

摘要: In this article, we evaluate glycosyl dithiocarbamates (DTCs) with unprotected C2 hydroxyls as donors in β-linked oligosaccharide synthesis. We report a mild, one-pot conversion of glycals into β-glycosyl DTCs via DMDO oxidation subsequent ring opening by DTC salts, which can be generated situ from secondary amines and CS2. Glycosyl are readily activated Cu(I) or Cu(II) triflate at low temperatures amenable to reiterative synthesis strategies, demonstrated the efficient construction tri-β-1,6-linked tetrasaccharide. couplings highly β-selective despite absence preexisting auxiliary group. provide evidence that directing effect is mediated hydroxyl itself putative formation cis-fused bicyclic intermediate.