Highly Efficient Regio- and Stereoselective Synthesis of β-(1→6)-Branched β-(1→3)-Linked Glucohexaose and Its Analogue

摘要

A β-(1→6)-branched β-(1→3)-linked glucohexaose (1) and its lauryl glycoside (2), present in many biologically active polysaccharides from traditional herbal medicines such as Ganoderma lucidum, Schizophyllum commune and Lentinus edodes, were highly efficiently synthesized. Coupling of 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl(1→3)-2-O-benzoyl-4,6-O-benzylidene-a-D-glucopyranosyl trichloroacetimidate (7) with 3,6-branched acceptors 8and 12 gave β-(1→3)-linked pentasaccharides (9) and (13), then via simple chemical transformation 4',6'-OH pentasaceharide acceptors 10 and 14 were obtained. Regio- and stereoselective coupling of 3 with 10 and 14 gave β-(1→3)-linked hexasaccharides (11) and (15) as the major products. Deprotection of 11 and 15 provided the target sugar 1 and 2. Thus, a new method for the preparation of this kind of compounds was developed.