Two isomeric pentasaccharides, β-D-Glcp-(1→3)-[β-D-Glcp-(1→6)]-β-D-Glcp-(1→3)-[β-D-Glcp-(1→6 )]-β-D-Glcp (I) and β-D-Glcp-(1→6)-β-D-Glcp-(1→3)-[β-D-Glcp-(1→3)-β-D-Glcp-(1→6)]-β-D-Glcp (II), the possible repeating unit of the β-glucan from the micro fungus Epicoccum nigrum Ehrenb. ex Schlecht, were synthesized as their 4-methoxyphenyl glycosides in a regio- and stereoselective manner. The pentasaccharide I was obtained from 3-O-selective glycosylation of 4-methoxyphenyl 4,6-O-benzylidene-β-D-glucopyranoside (12) with 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl-(1→3)-[2,3,4,6-tetra-O-benzoyl-be ta-D-glucopyranosyl-(1→6)]-2,4-di-O-acetyl-α-D-glucopyranosyl trichloroacetimidate (6) followed by acetylation, debenzylidenation, and 6-O-selective glucosylation with 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl trichloroacetimidate (1), and then by deprotection. The pentasaccharide II was obtained from 3-O-selective coupling of 12 with 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl-(1→6)-2,4-di-O-acetyl-3-O-allyl-a lpha-D-glucopyranosyl trichloroacetimidate (10) followed by acetylation, debenzylidenation, and 6-O-selective glycosylation with 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranosyl-(1→3)-2,4,6-tri-O-acetyl-α-D-glucopyranosyl trichloroacetimidate (11), and finally by deprotection.
Trichloroacetimidates, Regioselective synthesis, stereoselective synthesis, glucose oligosaccharides
Publication DOI: 10.1016/S0008-6215(02)00317-8Journal NLM ID: 0043535Publisher: Elsevier
Correspondence: fzkong@mail.rcees.ac.cn
Institutions: Research Center for Eco-Environmental Sciences, Academia Sinica, PO Box 2871, Beijing 100085, China
Methods: 13C NMR, 1H NMR, TLC, ESI-MS, CC, optical rotation, synthetic procedures
Found