title: Chiral-auxiliary-mediated 1,2-cis-glycosylations for the solid-supported synthesis of a biologically important branched alpha-glucan.
abstract: Solid-phase oligosaccharide synthesis offers the promise of providing libraries of oligosaccharides for glycomics research. A major stumbling block to solid-phase oligosaccharide synthesis has been a lack of general methods for the stereoselective installation of 1,2-cis-glycosides, and intractable mixtures of compounds are obtained if several such glycosides need to be installed. We have prepared on-resin a biologically important glucoside containing multiple 1,2-cis-glycosidic linkages with complete anomeric control by using glycosyl donors having a participating (S)-(phenylthiomethyl)benzyl chiral auxiliary at C2. A branching point could be installed by using 9-fluorenylmethyloxycarbonyl (Fmoc) and allyloxycarbonyl (Alloc) as a versatile set of orthogonal protecting groups. The synthetic strategy made it possible to achieve partial on-resin deprotection of the completed oligosaccharide, thereby increasing the overall efficiency of the synthesis. The combination of classical and auxiliary-mediated neighbouring-group participation for controlling anomeric selectivity is bringing the promise of routine automated solid-supported oligosaccharide synthesis closer.
authors.affiliation: Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GE 30602, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Boltje
authors.forename: Jin-Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Jin
authors.initials: J
authors.lastname: Park
authors.forename: Geert-Jan
authors.initials: GJ
authors.lastname: Boons
mesh_terms: D005936:Glucans / Q000138:chemical synthesis* / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism
chemical_list: D005936:Glucans; D006027:Glycosides