- Very high isotope incorporation in the C-1 position of glucose by exchange with deuterium or tritium gas
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The experimental conditions which control the exchange from deuterium or tritium gas into the C-1 proton position of glucose in aqueous solution have beep studied in detail, with a view to determining the factors which maximize exchange into glucose, but minimize exchange into the solvent water. The favoured conditions for producing glucose with close to 100% isotope labelling in the C-1 position, and with negligible formation of labelled byproducts, were a reaction time of 6 to 8 hours, a temperature of 60°C, and a pH of 7 or higher. Pd/BaSO4 was the preferred catalyst and slow pre-addition of the deuterium or tritium gas to the catalyst bed was essential to maximize the subsequent isotope exchange into the substrate.
- Long,Morimoto,Williams
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Read Online
- Synthesis of salacinol-D4 as an internal standard for mass-spectrometric quantitation of salacinol, a potent D-glucosidase inhibitor found in a traditional Ayurvedic medicine “Salacia”
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Accurate quantitative analysis of trace principles in extracts of biologically active natural medicines relies on the use of reliable internal standards (ISs), which, in the case of liquid chromatography-mass spectrometry (LC-MS) analysis, commonly corres
- Tanabe, Genzoh,Teramae, Sanami,Kunikata, Yousuke,Marumoto, Shinsuke,Okugawa, Shuhei,Ishikawa, Fumihiro,Xie, Weija,Morikawa, Toshio,Muraoka, Osamu
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p. 314 - 332
(2019/04/27)
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- PROCESS FOR PREPARING AN ENANTIOMERICALLY ENRICHED, DEUTERATED SECONDARY ALCOHOL FROM A CORRESPONDING KETONE WITHOUT REDUCING DEUTERIUM INCORPORATION
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The present invention provides a convenient and efficient process for the preparation of enantiomerically enriched, deuterated secondary alcohols without reducing deuterium incorporation.
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Page/Page column 23
(2012/03/26)
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- Catalytic reaction mechanism based on α-secondary deuterium isotope effects in hydrolysis of trehalose by European honeybee trehalase
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Trehalase, an anomer-inverting glycosidase, hydrolyzes only α, α-trehalose in natural substrates to release equimolecular β-glucose and α-glucose. Since the hydrolytic reaction is reversible, α, α-[1, 1′-2H]trehalose is capable of synthesis from [1-2H]glucose through the reverse reaction of trehalase. α-Secondary deuterium kinetic isotope effects (α-SDKIEs) for the hydrolysis of synthesized α, α-[1, 1′-2H]trehalose by honeybee trehalase were measured to examine the catalytic reaction mechanism. Relatively high kH/kD value of 1.53 for α-SDKIEs was observed. The data imply that the catalytic reaction of the trehalase occurs by the oxocarbenium ion intermediate mechanism. In addition, the hydrolytic reaction of glycosidase is discussed from the viewpoint of chemical reactivity for the hydrolysis of acetal in organic chemistry. As to the hydrolytic reaction mechanism of glycosidases, oxocarbenium ion intermediate and nucleophilic displacement mechanisms have been widely recognized, but it is pointed out for the first time that the former mechanism is rational and valid and generally the latter mechanism is unlikely to occur in the hydrolytic reaction of glycosidases.
- Mori, Haruhide,Lee, Jin-Ha,Okuyama, Masayuki,Nishimoto, Mamoru,Ohguchi, Masao,Kim, Doman,Kimura, Atsuo,Chiba, Seiya
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experimental part
p. 2466 - 2473
(2010/08/06)
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- A kinetic isotope effect study on the hydrolysis reactions of methyl xylopyranosides and methyl 5-thioxylopyranosides: Oxygen versus sulfur stabilization of carbenium ions
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The following kinetic isotope effects, KIEs (klight/kheavy), have been measured for the hydrolyses of methyl α- and β-xylopyranosides, respectively, in aqueous HClO4 (μ = 1.0 M, NaClO4) at 80 °C: α-D, 1.128 ± 0.004, 1.098 ± 0.005; β-D, 1.088 ± 0.008, 1.042 ± 0.004; γ-D2, (C5) 0.986 ± 0.001, 0.967 ± 0.003; leaving-group 18O, 1.023 ± 0.002, 1.023 ± 0.003; ring 18O, 0.983 ± 0.001, 0.978 ± 0.001; anomeric 13C, 1.006 ± 0.001, 1.006 ± 0.003; and solvent, 0.434 ± 0.017, 0.446 ± 0.012. In conjunction with the reported (J. Am. Chem. Soc. 1986, 108, 7287-7294) KIEs for the acid-catalyzed hydrolysis of methyl α- and β-glucopyranosides, it is possible to conclude that at the transition state for xylopyranoside hydrolysis resonance stabilization of the developing carbenium ion by the ring oxygen atom is coupled to exocyclic C-O bond cleavage, and the corresponding methyl glucopyranosides hydrolyze via transition states in which charge delocalization lags behind aglycon departure. In the analogous hydrolysis reactions of methyl 5-thioxylopyranosides, the measured KIEs in aqueous HClO4 (μ = 1.0 M, NaClO4) at 80 °C for the α- and β-anomers were, respectively, α-D, 1.142 ± 0.010, 1.094 ± 0.002; β-D 1.061 ± 0.003, 1.0185 ± 0.001; γ-D2, (C5) 0.999 ± 0.001, 0.986 ± 0.002; leaving-group 18O, 1.027 ± 0.001, 1.035 ± 0.001; anomeric 13C, 1.031 ± 0.002, 1.028 ± 0.002; solvent, 0.423 ± 0.015, 0.380 ± 0.014. The acid-catalyzed hydrolyses of methyl 5-thio-α- and β-xylopyranosides, which occur faster than methyl α- and β-xylopyranosides by factors of 13.6 and 18.5, respectively, proceed via reversibly formed O-protonated conjugate acids that undergo slow, rate-determining exocyclic C-O bond cleavage. These hydrolysis reactions do not have a nucleophilic solvent component as a feature of the thiacarbenium ion-like transition states.
- Indurugalla,Bennet
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p. 10889 - 10898
(2007/10/03)
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- Biosynthesis of Natural Products with a P-C Bond, X. Incorporation of D-1>Glucose into 2-Aminoethylphosphonic Acid in Tetrahymena thermophila and into Fosfomycin in Streptomyces fradiae. - The Stereochemical Course of a Phosphoenolpyruvate Mutase-Catalyzed Reaction
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2-Aminoethylphosphonic acid and fosfomycin produced on feeding D-1>glucose to Tetrahymena thermophila and Streptomyces fradiae, respectively, indicate that the phosphoenolpyruvate mutase catalyzes the stereospecific transfer of the phospho group of (Z)-phosphoenol-1>pyruvate from oxygen to carbon from the si face. 2H-NMR spectroscopy was used to determine the configuration at C-1 of biosynthetically formed 2-amino-1>ethylphosphonic acid after derivatization with (-)-camphanoyl chloride and diazomethane.Key Words: Phosphoenolpyruvate mutase / (Z)-Phosphoenol-1>pyruvate / D-1>Glucose / Ethylphosphonic acids / Fosfomycin / Tetrahymena thermophila / Streptomyces fradiae
- Hammerschmidt, Friedrich,Kaehlig, Hanspeter
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p. 1201 - 1204
(2007/10/02)
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