498-43-1Relevant academic research and scientific papers
Alkoxycarbonyl elimination of 3-O-substituted glucose and fructose by heat treatment under neutral pH
Aramasa, Hiroki,Chiku, Kazuhiro,Kitaoka, Motomitsu,Nakai, Hiroyuki,Nihira, Takanori,Ono, Hiroshi,Teshima, Yu,Tsukasaki, Riku,Yoshida, Mitsuru
, (2020/08/28)
3-O-Substituted reducing aldoses are commonly unstable under heat treatment at neutral and alkaline pH. In this study, to evaluate the decomposition products, nigerose (3-O-α-D-glucopyranosyl-D-glucose) and 3-O-methyl glucose were heated at 90 °C in 100 mM sodium phosphate buffer (pH 7.5). Decomposition via β-elimination was observed that formed a mixture of 3-deoxy-arabino-hexonic acid and 3-deoxy-ribo-hexonic acid; upon further acid treatment, it was converted to their γ-lactones. Similarly, turanose (3-O-α-D-glucopyranosyl-D-fructose), a ketose isomer of nigerose, decomposed more rapidly than nigerose under the same conditions, forming the same products. These findings indicate that 3-O-substituted reducing glucose and fructose decompose via the same 1,2-enediol intermediate. The alkoxycarbonyl elimination of 3-O-substituted reducing glucose and fructose occurs readily if an O-glycosidic bond is located on the carbon adjacent to the 1,2-enediol intermediate. Following these experiments, we proposed a kinetic model for the3- decomposition of nigerose and turanose by heat treatment under neutral pH conditions. The proposed model showed a good fit with the experimental data collected in this study. The rate constant of the decomposition for nigerose was (1.2 ± 0.1) × 10?4 s?1, whereas that for turanose [(2.6 ± 0.2) × 10?4 s?1] was about 2.2 times higher.
Alkaline degradation of monosaccharides III. Influence of reaction parameters upon the final product composition
Bruijn, J. M. de,Kieboom, A. P. G.,Bekkum, H. van
, p. 176 - 183 (2007/10/02)
A systematic investigation of the alkaline degradation of monosaccharides is presented.The influence of several parameters upon the degradation reaction has been determined by analysis of the reaction products using HPLC and, in some cases, GC.The HO- and the monosaccharide concentrations markedly influence the final product composition with respect to both the amount of C1 to C6 acids and the formation of oligomeric acidic products, the so-called > C6 acids.Maximum yields of these > C6 acids, up to 50 mol-C6-percent, are obtained at an HO- concentration of between 1E-3 M and 1E-2 Mwhen the monosaccharide concentration exceeds 1E-2 M.The presence of divalent calcium increases the retro-aldolization of monosaccharides in alkaline medium, as illustrated by the enhanched production of lactic acid, by complexation with, for instance, D-fructose.Borate partly protects monosaccharides against alkaline degradation through their borate esters, whilst the amount of saccharinic acids in the degradation product mixture is doubled.On the other hand, neither chloride and carbonate nor the reaction temperature influences the final product composition.Alkaline degradation experiments with pyruvaldehyde, glyceraldehyde and 1,3-dihydroxyacetone, all assumed to be reaction intermediates, indicate that aldolization of (di)carbonyl compounds causes the formation of substantial amounts of >C6 acids.
Structure of the K95 antigen from Escherichia coli O75:K95:H5, a capsular polysaccharide containing furanosidic KDO-residues.
Dengler,Jann,Jann
, p. 269 - 276 (2007/10/02)
The structure of the K95 antigenic capsular polysaccharide (K95 antigen) of Escherichia coli O75:K95:H5 was elucidated by determination of the composition, 1H- and 13C-n.m.r. spectroscopy, periodate oxidation, and methylation analysis. The K95 polysaccharide, which contains furanosidic 3-deoxy-D-manno-2-octulosonic acid (KDOf) residues, consists of----3)-beta-D-Rib-(1----8)-KDOf-(2----repeating units, has a molecular weight of approximately 25,000 (approximately 65 repeating units), and is randomly O-acetylated (1 acetyl group per repeating unit at unknown positions).
