SYNTHESES OF A BRANCHED HEPTASACCHARIDE HAVING PHYTOALEXIN-ELICITOR ACTIVITY

Article abstract of DOI:10.1016/0008-6215(87)80137-4

Synteses are described of a D-glucose heptasaccharide, 1, corresponding to a glucan structure recognised by the soybean when infected by the fungus Phytophtora megasperma f. sp. glycinea and which stimulates the formation of phytoalexins.The synthetic strategy is based upon 1,2-trans-glycoside formation assisted by participating benzoate groups in the 2-position, with silver triflate as promoter and glycosyl bromides as donors for making the smaller fragments, and with methyl triflate as promoter with thioglycosides as donors for making the larger ones.Regioselective reductive openings of 4,6 benzylidene acetals play a key role in obtaining free 6-OH groups with benzyl protection at O-4.