title: Synthesis of two isomeric pentasaccharides, the possible repeating unit of the beta-glucan from the micro fungus Epicoccum nigrum Ehrenb. ex Schlecht.
abstract: Two isomeric pentasaccharides, beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->6)]-beta-D-Glcp (I) and beta-D-Glcp-(1-->6)-beta-D-Glcp-(1-->3)-[beta-D-Glcp-(1-->3)-beta-D-Glcp-(1-->6)]-beta-D-Glcp (II), the possible repeating unit of the beta-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-beta-D-glucopyranoside (12) with 2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->3)-[2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->6)]-2,4-di-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (6) followed by acetylation, debenzylidenation, and 6-O-selective glucosylation with 2,3,4,6-tetra-O-benzoyl-beta-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-beta-D-glucopyranosyl-(1-->6)-2,4-di-O-acetyl-3-O-allyl-alpha-D-glucopyranosyl trichloroacetimidate (10) followed by acetylation, debenzylidenation, and 6-O-selective glycosylation with 2,3,4,6-tetra-O-benzoyl-beta-D-glucopyranosyl-(1-->3)-2,4,6-tri-O-acetyl-alpha-D-glucopyranosyl trichloroacetimidate (11), and finally by deprotection.
authors.affiliation: Research Center for Eco-Environmental Sciences, Academia Sinica, PO Box 2871, Beijing 100085, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zeng
authors.forename: Wenhui
authors.initials: W
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Ning
authors.forename: Fanzuo
authors.initials: F
authors.lastname: Kong
mesh_terms: D001203:Ascomycota / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D005936:Glucans / Q000737:chemistry*; D005960:Glucosides; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis*
chemical_list: D005936:Glucans; D005960:Glucosides; D009844:Oligosaccharides