title: Semisynthesis of Intact Complex-Type Triantennary Oligosaccharides from a Biantennary Oligosaccharide Isolated from a Natural Source by Selective Chemical and Enzymatic Glycosylation.
abstract: Attachment of oligosaccharides to proteins is a major post-translational modification. Chemical syntheses of oligosaccharides have contributed to clarifying the functions of these oligosaccharides. However, syntheses of oligosaccharide-linked proteins are still challenging because of their inherent complicated structures, including diverse di- to tetra-antennary forms. We report a highly efficient strategy to access the representative two types of triantennary oligosaccharides through only 9- or 10-step chemical conversions from a biantennary oligosaccharide, which can be isolated in exceptionally homogeneous form from egg yolk. Four benzylidene acetals were successfully introduced to the terminal two galactosides and two core mannosides of the biantennary asialononasaccharide bearing 24 hydroxy groups, followed by protection of the remaining hydroxy groups with acetyl groups. Selective removal of one of the benzylidene acetals gave two types of suitably protected glycosyl acceptors. Glycosylation toward the individual acceptors with protected Gal-β-1,4-GlcN thioglycoside and subsequent deprotection steps successfully yielded two types of complex-type triantennary oligosaccharides.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Maki
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Okamoto
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Izumi
authors.affiliation: International Graduate School of Arts and Science, Yokohama City University , 22-2 Seto, Kanazawa-ku, Yokohama, Kanagawa 236-0027, Japan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Murase
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University , 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kajihara
mesh_terms: D001597:Benzylidene Compounds / Q000737:chemistry; D002240:Carbohydrate Sequence; D006031:Glycosylation; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000378:metabolism
chemical_list: D001597:Benzylidene Compounds; D009844:Oligosaccharides