- Selective and Scalable Synthesis of Sugar Alcohols by Homogeneous Asymmetric Hydrogenation of Unprotected Ketoses
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Sugar alcohols are of great importance for the food industry and are promising building blocks for bio-based polymers. Industrially, they are produced by heterogeneous hydrogenation of sugars with H2, usually with none to low stereoselectivities. Now, we present a homogeneous system based on commercially available components, which not only increases the overall yield, but also allows a wide range of unprotected ketoses to be diastereoselectively hydrogenated. Furthermore, the system is reliable on a multi-gram scale allowing sugar alcohols to be isolated in large quantities at high atom economy.
- Tindall, Daniel J.,Mader, Steffen,Kindler, Alois,Rominger, Frank,Hashmi, A. Stephen K.,Schaub, Thomas
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supporting information
p. 721 - 725
(2020/10/19)
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- A PROCESS FOR THE HYDROGENATION OF A SUGAR OR SUGAR MIXTURE
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A process for the hydrogenation of a ketose or a ketose-containing sugar mixture to produce a product mixture comprising at least two stereoisomeric sugar alcohols is disclosed. The process comprises the provision of a reaction mixture comprising said ketose or ketose-containing sugar mixture, the addition of a concentration of solid nickel-based catalyst to said reaction mixture, and conducting a hydrogenation reaction in said reaction mixture in the presence of hydrogen gas. With this process, it is possible to obtain a predefined ratio of cis-isomer to trans-isomer of the two stereoisomeric sugar alcohols. The ratio of cis-isomer to trans-isomer can be decreased by increasing the concentration of solid nickel-based catalyst, by decreasing the starting temperature of the heating step, and/or by decreasing the heating rate of the heating step.
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Page/Page column 10-13; 16-20
(2008/12/06)
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- Oligosaccharide synthesis by dextransucrase: New unconventional acceptors
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The acceptor reactions of dextransucrase offer the potential for a targeted synthesis of a wide range of di-, tri- and higher oligosaccharides by the transfer of a glucosyl group from sucrose to the acceptor. We here report on results which show that the synthetic potential of this enzyme is not restricted to 'normal' saccharides. Additionally functionalized saccharides, such as alditols, aldosuloses, sugar acids, alkyl saccharides, and glycals, and rather unconventional saccharides, such as fructose dianhydride, may also act as acceptors. Some of these acceptors even turned out to be relatively efficient: α-D-glucopyranosyl-(1→5)-D-arabinonic acid, α-D-glucopyranosyl-(1→4)-D-glucitol, α-D-glucopyranosyl-(1→6)-D-glucitol, α-D-glucopyranosyl-(1→6)-D-mannitol, α-D-fructofuranosyl-β-D-fructofuranosyl-(1,2′:2,3′)- dianhydride, 1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol ('-glucal'), and may therefore be of interest for future applications of the dextransucrase acceptor reaction.
- Demuth, Kristin,J?rdening, Hans-Joachim,Buchholz, Klaus
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p. 1811 - 1820
(2007/10/03)
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- Identification of alpha-D-glucosylglycerol in sake.
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alpha-D-Glucosylglycerol (GG) was found for the first time in sake (Japanese rice wine) in an amount of about 0.5%. GG was also found in miso and mirin which had been brewed by using koji. GG was hydrolyzed into glucose and glycerol in an equimolar ratio with maltase (EC 3.2.1.20, alpha-glucosidase from yeast), but not with emulsin (EC 3.2.1.21, beta-glucosidase from almond). The retention times and mass spectra of trimethylsilyl derivatives by a GC-MS analysis of GG in sake were comparable to those of various GG samples synthesized by glycol cleavage. It was proven that GG in sake consisted of three components, viz., 2-O-alpha-D-glucosyl-glycerol (GG-II), (2R)-1-O-alpha-D-glucosylglycerol (R-GG-I) and (2S)-1-O-alpha-D-glucosylglycerol (S-GG-I). The ratio of the three components in GG was 6:66:28 for sake. It is considered that GG was formed by transglucosylation of the glucosyl groups to glycerol by alpha-glucosidase from koji in the sake mash.
- Takenaka,Uchiyama,Imamura
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p. 378 - 385
(2007/10/03)
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- SELECTIVE DEGRADATION OF THE GLYCOSYLURONIC ACID RESIDUES OF COMPLEX CARBOHYDRATES BY LITHIUM DISSOLVED IN ETHYLENEDIAMINE
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Lithium metal dissolved in ethylenediamine had been demonstrated to cleave a 3-linked glycosyluronic acid-containing polysaccharide .The present study with model compounds has established that, by lithium treatment, carbohydrates are cleaved at the sites of the glycosyluronic acid residues, regerdless of the point at which other glycosyl residues are attached to the glycosyluronic acid residue.Treatment of carbohydrates with lithium metal dissolved in ethylenediamine also results in cleavage of methyl glycosides, reduction of aldoses, and cleavage of methyl ethers and pyruvic acetals of glycosyl residues.Model compounds were used to demonstrate that oligosaccharides containing only neutral glycosyl residues are largely stable to the reaction conditions (except for the reduction of the glycose residue of each oligosaccharide).Thus, a general procedure for the selective cleavage of underivatized carbohydrates at the glycosyluronic acid residues is described.
- Lau, James M.,McNeil, Michael,Darvill, Alan G.,Albersheim, Peter
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p. 219 - 244
(2007/10/02)
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- HYDROGENATION OF D-FRUCTOSE AND D-FRUCTOSE/D-GLUCOSE MIXTURES
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D-Fructose and D-fructode/D-glucose mixtures have been hydrogenated in water at 60-80 deg and 20-75 atm. of hydrogen with Ni, Cu, Ru, Rh, Pd, Os, Ir, and Pt severally as catalysts.The selectivity for the formation of D-mannitol from D-fructose as well as the selectivity for the hydrogenation of D-fructose in the presence of D-glucose with Cu/silica as the catalyst are substantially higher than those for the other catalysts.With Cu/silica as the catalyst, the hydrogenation of D-fructose is first order with respect to the amount of catalyst and the hydrogen pressure, whereas a shift from first- to zero-order kinetics occurs on going from low (0.8) concentrations of D-fructose.D-Fructose is preferentially hydrogenated via its furanose forms, presumably by attack of a copper hydride-like species at the anomeric carbon atom with inversion of configuration.Preferential adsorption of pyranose with respect to furanose forms occurs, whereas the furanose forms show a much higher reactivity.The mechanism proposed for the copper-catalyzed hydrogenation reaction explains both the enhanced yield of D-mannitol from boric esters of D-fructose and the diastereoselectivity of the hydrogeantion of seven other ketoses.
- Makkee, Michiel,Kieboom, P. G.,Bekkum, Herman van
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p. 225 - 236
(2007/10/02)
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