Synthesis of a heptasaccharide, structurally related to the phytoelicitor active glucan of Phytophthora megasperma f.sp. glycinea

A synthesis is described of the heptasaccharide 1, which may form part of the phytoelicitor-active glucan of Phytopkthora megasperma f. sp. glycinea. Silver triflate was used as the promoter in Koenigs-Knorr type condensations using glycosyl bromides, each with a participating benzoyl group in the 2-position, for the synthesis of the smaller oligosaccharide fragments. For joining the larger ones, methyl triflate was used as the promoter and an oligosaccharide thioglycoside carrying a participating benzoyl group in the 2-position was used as the glycosyl donor.