Convergent and Convenient Total Synthesis of Phytoalexin-Elicitor Active Heptasaccharide by One-Pot Sequential Glycosylation

Convergent and convenient total synthesis of branched hepta-β-glucoside 1 having phytoalexin-elicitor activity was efficiently accomplished by way of two one-pot sequential glycosylation reactions. Trisaccharide 8 was synthesized in high yield by TfOH-catalyzed one-pot glycosylation using three component monosaccharides and subsequent selective deprotection of a 6′-O-TBDPS group. The second one-pot glycosylation of trisaccharide 8 with the three monosaccharides smoothly proceeded to afford heptaglucoside 11 stereoselectively in 48% total yield based on monosaccharide 3. The targeted compound 1 was obtained in high yield after the removal of the protecting groups.