Syntheses of a Heptasaccharide β-Linked to an 8-Methoxy-Carbonyl-Oct-1-Yl Linking Arm and of a Decasaccharide with Structures Corresponding to the Phytoelicitor Active Glucan of<i>Phytophthora Megasperma</i><b>F.</b><i>Sp. Glycinea</i>

Abstract

Abstract Syntheses are described of the 8-methoxycarbonyloct-1-yl β-D-glycoside of 32,34-di-β-D-glucopyranosylgentiopentaose and also of 32,34,36-tri-β-D-glucopyranosylgentioheptaose, both of which were required for phytochemical studies of the defense mechanism of the soybean plant to infection by the mould Phytophthora megasperma f.sp. glycinea. Block synthesis strategies were used, relying on promotion by methyl triflate and the use of thioglycosides as glycosyl donors in the condensation of the oligosaccharide fragments. Highly stereoselective β-D-glycosylation was ensured by the presence of benzoyl groups in the 2-positions of the glycosyl donors.