title: O-alkylation at the anomeric centre for the stereoselective synthesis of Kdo-alpha-glycosides.
abstract: O-Alkylation at the anomeric centre of the dianion of 4,5:7,8-di-O-cyclohexylidene-3-deoxy-N-methyl-alpha-D-manno- octulopyranosonamide (1) with several triflates led diastereoselectively to the alpha-glycosides. In this way, lipopolysaccharide building-blocks containing alpha-Kdo-(2----6)-GlcN and alpha-Kdo-(2----6)-beta-GlcN-(1----6)-GlcN moieties were obtained and deployed in the synthesis of decyl 4,5,7,8-tetra-O-acetyl-3-deoxy-N-methyl-alpha-D-manno-2-octulopyranos idonamide (18), 2,3-di-O-tetradecanoyl-D-glycer-1-yl 4,5,7,8-tetra-O-acetyl-3-deoxy-N-methyl- alpha-D-manno-2-octulopyranosid-onamide (22), methyl 2,3,4-tri-O-acetyl-6-O-(methyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D- manno-2-octulopyranosylonate)-alpha-D-glucopyranoside (28), 1-O-acetyl-2-deoxy-6-O-(methyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2- octulopyranosylonate)-2-tetradecanoylamino-alpha-D-glucopyra nose (33), tert-butyldimethylsilyl O-(methyl 4,5:7,8-di-O-cyclohexylidene-3-deoxy-alpha-D- manno-2-octulopyranosylonate)-(2----6)-O-(3,4-di-O-benzyl-2-deoxy- 2- tetradecanoylamino-beta-D-glucopyranosyl)-(1----6)-3,4-di-O-benzyl -2-deoxy-2- tetradecanoylamino-alpha-D-glucopyranoside (36).
authors.affiliation: Fakultät für Chemie, Universität Konstanz, F.R.G.
authors.forename: A
authors.initials: A
authors.lastname: Esswein
authors.forename: H
authors.initials: H
authors.lastname: Rembold
authors.forename: R R
authors.initials: RR
authors.lastname: Schmidt
mesh_terms: D000478:Alkylation; D002240:Carbohydrate Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D006027:Glycosides / Q000138:chemical synthesis*; D008969:Molecular Sequence Data; D013237:Stereoisomerism; D013400:Sugar Acids
chemical_list: D006027:Glycosides; D013400:Sugar Acids; C002532:2-keto-3-deoxyoctonate