title: Synthesis and NMR spectroscopy of nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids.
abstract: Derivatives of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids are essential constituents of some bacterial polysaccharides and glycoproteins. In order to establish reliably the configuration of the natural sugars, nine stereoisomeric 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acids were synthesized, including di-N-acetyl-legionaminic and -pseudaminic acids (the D-glycero-D-galacto and L-glycero-L-manno isomers, respectively) and their isomers at C-4, C-5, C-7, and C-8 having the L-glycero-D-galacto, D-glycero-D-talo, L-glycero-D-talo, D-glycero-L-altro, L-glycero-L-altro, D-glycero-L-manno, and L-glycero-L-gluco configurations. Synthesis was performed by condensation of 2,4-diacetamido-2,4,6-trideoxy-L-gulose, -D-mannose, -D-talose, and -L-allose with oxalacetic acid under basic conditions, the reaction of the last two precursors being accompanied by epimerisation at C-2. The 1H and 13C NMR data of the synthetic compounds are discussed. Acetylated methyl esters of the C-7 and C-8 isomeric nonulosonic acids were prepared and used for analysis of the side-chain conformation by NMR spectroscopy.
authors.affiliation: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospeckt 47, 119991 Moscow, Russian Federation. tsvetkov@ioc.ac.ru
authors.forename: Y E
authors.initials: YE
authors.lastname: Tsvetkov
authors.forename: A S
authors.initials: AS
authors.lastname: Shashkov
authors.forename: Y A
authors.initials: YA
authors.lastname: Knirel
authors.forename: U
authors.initials: U
authors.lastname: Zähringer
mesh_terms: D005942:Gluconates / Q000138:chemical synthesis* / Q000737:chemistry; D005947:Glucose / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008358:Mannose / Q000737:chemistry; D010071:Oxaloacetates / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D012794:Sialic Acids / Q000138:chemical synthesis / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D005942:Gluconates; D010071:Oxaloacetates; D011135:Polysaccharides, Bacterial; D012794:Sialic Acids; C050215:5,7-diacetamido-3,5,7,9-tetradeoxy-glycerogalacto-nonulosonic acid; C002055:allose; D005947:Glucose; D008358:Mannose