Dodecyl thioglycosides (3, 4, 5) were prepared by conventional transformation of D-glucose and used as new glycosyl donors for a short-step synthesis of phytoalexin elicitor heptaglucoside. A gentio-tetraoside derivative (6) having three hydroxyl groups was synthesized by NIS–TfOH promoted glycosylate in more than 90% yield followed by selective removal of temporary protective groups. Undesired formation of α-glycosides at the introduction of β-(1→3)-branches into gentio-oligosaccharides was found to be suppressed by use of a thiophilic reagent system, BSP (1-benzenesulfinyl piperidine)–Tf2O, giving the heptaglucoside in only four glycosylation steps.
