title: An alternative access to a trisaccharide repeating unit of the capsular polysaccharide of Streptococcus pneumoniae serotype 19A.
abstract: A chemical synthesis has been achieved for beta-D-ManNAc-(1-->4)-alpha-D-Glc-(1-->3)-L-Rha, a trisaccharide repeating unit of the capsular polysaccharide of Streptococcus pneumoniae serotype 19A, by stepwise link-up of the suitably functionalized, constituent sugar units. A beta-selective glycosylation of trimethylsilylethyl glucoside having free 4-OH with 2-(benzoyloxyimino)-2-deoxyglycosyl bromide, followed by manno-selective hydroboration, N-acetylation, and functionalization of the anomeric center (1-OSE-->1-OH-->1-F), gave a key disaccharide donor, beta-D-ManNAc-(1-->4)-alpha-D-Glc-(1-->F. Ensuing glycosylation of an L-rhamnosyl acceptor with the donor substrate afforded, after deblocking, the target trisaccharide in 6.5% yield over 13 steps from D-glucose.
authors.affiliation: School of Pharmaceutical Sciences, Kitasato University, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Kaji
authors.forename: Y
authors.initials: Y
authors.lastname: Osa
authors.forename: M
authors.initials: M
authors.lastname: Tanaike
authors.forename: Y
authors.initials: Y
authors.lastname: Hosokawa
authors.forename: H
authors.initials: H
authors.lastname: Takayanagi
authors.forename: A
authors.initials: A
authors.lastname: Takada
mesh_terms: D002240:Carbohydrate Sequence; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry*; D013296:Streptococcus pneumoniae / Q000737:chemistry*
chemical_list: D011134:Polysaccharides