A general strategy for the synthesis of 3,6-branched gluco-oligosaccharides: facile synthesis of the phytoalexin elicitor oligosaccharides

A general method for the synthesis of 3,6-branched gluco-oligosaccharides has been developed. As a typical example of the method, the synthesis of the glucohexatose phytoalexin elicitor on a large scale was achieved via coupling of a trisaccharide donor with a trisaccharide acceptor. The donor and acceptor were prepared easily from 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose, 2,3,4,6-tetra-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate, and 6-O-acetyl-2,3,4-tri-O-benzoyl-α-d-glucopyranosyl trichloroacetimidate in a regio- and stereoselective manner. Higher oligosaccharides of the elicitor including the hepta-, nona-, dodeca- and tetradecasaccharides have also been readily synthesized by this strategy.