Synthesis of di-branched heptasaccharide by one-pot glycosylation using seven independent building blocks

(Equation presented) We describe an efficient synthesis of di-branched heptasaccharide 1 having phytoalexin elicitor activity in soybeans by one-pot glycosylation. The synthesis involves chemo-and regioselective sequential six-step glycosylations using seven independent building blocks and sequential removal of acyl-and benzyl ether-type protecting groups. The coupling of seven building blocks requires only four chemoselective activitable leaving groups of glycosyl donors. Both the glycosylation and deprotection reactions can be achieved utilizing a parallel manual synthesizer.