title: Synthesis of an xylosylated rhamnose pentasaccharide, the repeating unit of the O-chain polysaccharide of the lipopolysaccharide of Xanthomonas campestris pv. begoniae GSPB 525.
abstract: A xylosylated rhamnose pentasaccharide, alpha-L-Rhap-(1-->3)-[beta-L-Xylp-(1-->2)-]-alpha-L-Rhap-(1-->3)-[beta-L-Xylp-(1-->4)]-L-Rhap, the repeating unit of the O-chain polysaccharide (OPS) of the lipopolysaccharides of Xanthomonas campestris pv. begoniae GSPB 525 was synthesized by a highly regio- and stereoselective way. Thus coupling of 1,2-O-ethylidene-beta-L-rhamnopyranose (1) with 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl trichloroacetimidate (2) to give (1-->3)-linked disaccharide (3), subsequent benzoylation, deethylidenation, acetylation, 1-O-deacetylation, and trichloroacetimidation afforded the disaccharide donor 11. Condensation of 11 with 1 yielded 2,3,4-tri-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->3)-2-O-acetyl-4-O-benzoyl-alpha-L-rhamnopyranosyl-(1-->3)-1,2-O-ethylidene-beta-L-rhamnopyranose (12), and selective deacetylation of 12 yielded the trisaccharide diol acceptor 15. Coupling of 15 with 2,3,4-tri-O-benzoyl-alpha-L-xylopyranosyl trichloroacetimidate (16), followed by deprotection, gave the target pentasaccharide 19.
authors.affiliation: Research Center for Eco-Environmental Sciences, Academia Sinica, PO Box 2871, 100085, Beijing, PR China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Zhang
authors.forename: Fanzuo
authors.initials: F
authors.lastname: Kong
mesh_terms: D002240:Carbohydrate Sequence; D008070:Lipopolysaccharides / Q000737:chemistry*; D019081:O Antigens / Q000737:chemistry*; D009844:Oligosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D012210:Rhamnose / Q000737:chemistry*; D013329:Structure-Activity Relationship; D016959:Xanthomonas campestris / Q000737:chemistry*; D014994:Xylose / Q000737:chemistry
chemical_list: D008070:Lipopolysaccharides; D019081:O Antigens; D009844:Oligosaccharides; D014994:Xylose; D012210:Rhamnose