title: A practical synthesis of alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->2)-[alpha-D-Glcp-(1-->3)]-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp, an O-specific heterohexasaccharide fragment of Citrobacter braakii O7a, 3b, 1c.
abstract: An O-specific heterohexasaccharide fragment of Citrobacter braakii O7a, 3b, 1c, alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->2)-[alpha-D-Glcp-(1-->3)]-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp was synthesized as its methyl glycoside. Acetylation of allyl 4,6-O-benzylidene-alpha-D-mannopyranoside, followed by debenzylidenization and benzoylation gave allyl 2,3-di-O-acetyl-4,6-di-O-benzoyl-alpha-D-mannopyranoside (3), and subsequent deacetylation of 3 with CH(3)COCl-MeOH gave the monosaccharide acceptor 4. Condensation of isopropyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-glucopyranoside (6) with 4 selectively afforded the alpha-(1-->3)-linked disaccharide 7. Condensation of 7 with the (1-->3)-linked disaccharide donor 9, followed by deallylation and trichloroacetimidation, afforded the tetrasaccharide donor 12. Coupling of 12 with disaccharide acceptor 13, followed by debenzylation and deacylation, furnished the target heterohexasaccharide 16.
authors.affiliation: Chinese Academy of Sciences, Academia Sinica, Research Center for Eco-Environmental Sciences, P.O. Box 2871, Beijing 100085, PR China
authors.forename: Langqiu
authors.initials: L
authors.lastname: Chen
authors.forename: Fanzuo
authors.initials: F
authors.lastname: Kong
mesh_terms: D002240:Carbohydrate Sequence; D002954:Citrobacter / Q000737:chemistry*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry*
chemical_list: D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial