20248-27-5Relevant articles and documents
Expanding the reaction space of aldolases using hydroxypyruvate as a nucleophilic substrate
De Berardinis, Véronique,Guérard-Hélaine, Christine,Darii, Ekaterina,Bastard, Karine,Hélaine, Virgil,Mariage, Aline,Petit, Jean-Louis,Poupard, Nicolas,Sánchez-Moreno, Israel,Stam, Mark,Gefflaut, Thierry,Salanoubat, Marcel,Lemaire, Marielle
supporting information, p. 519 - 526 (2017/08/14)
Aldolases are key biocatalysts for stereoselective C-C bond formation allowing access to polyoxygenated chiral units through direct, efficient, and sustainable synthetic processes. The aldol reaction involving unprotected hydroxypyruvate and an aldehyde offers access to valuable polyhydroxy-α-keto acids. However, this undescribed aldolisation is highly challenging, especially regarding stereoselectivity. This reaction was explored using, as biocatalysts, a collection of aldolases selected from biodiversity. Several enzymes that belong to the same pyruvate aldolase Pfam family (PF03328) were found to produce the desired hexulosonic acids from hydroxypyruvate and d-glyceraldehyde with complementary stereoselectivities. One of them was selected for the proof of concept as a biocatalytic tool to prepare five (3S,4S) aldol adducts through an eco-friendly process.
AuPt Alloy on TiO2: A Selective and Durable Catalyst for l-Sorbose Oxidation to 2-Keto-Gulonic Acid
Chan-Thaw, Carine E.,Chinchilla, Lidia E.,Campisi, Sebastian,Botton, Gianluigi A.,Prati, Laura,Dimitratos, Nikolaos,Villa, Alberto
, p. 4189 - 4194 (2015/12/30)
Pt nanoparticles were prepared by a sol immobilization route, deposited on supports with different acid/base properties (MgO, activated carbon, TiO2, Al2O3, H-Mordenite), and tested in the selective oxidation of sorbose to 2-keto-gulonic acid (2-KGUA), an important precursor for vitamin C. In general, as the basicity of the support increased, a higher catalytic activity occurred. However, in most cases, a strong deactivation was observed. The best selectivity to 2-KGUA was observed with acidic supports (TiO2 and H-Mordenite) that were able to minimize the formation of C1/C2 products. We also demonstrated that, by alloying Pt to Au, it is possible to enhance significantly the selectivity of Pt-based catalysts. Moreover, the AuPt catalyst, unlike monometallic Pt, showed good stability in recycling because of the prevention of metal leaching during the reaction.
Oxidation of carbohydrates of biological importance by the aquachromium(IV) ion
González, Juan Carlos,Mangiameli, María Florencia,Asis, Agostina Crotta,Bellú, Sebastián,Sala, Luis F.
, p. 84 - 92 (2013/03/28)
The oxidation reactions kinetics of a series of related saccharides by aqua-oxo chromium(IV) ion, (H2O)5CrIVO 2+, were carried out in perchloric acid aqueous solutions. These reactions yield superoxochromium(III) ion, CrO22+, providing evidence that the two-electron reduction of CrO2+ to Cr2+ occurred in a single step. In all of these reactions, Cr 2+ is the immediate product and could be trapped as CrO 22+ when an excess of oxygen was present. The bimolecular rate constants for different aldoses and d-glucitol are independent of [H +] in the range 0.1-1.0 M. Relative reactivities of these saccharides toward CrO2+ reduction are 1-methyl-α-d-glucopyranose 2+ showed the same mechanism but the redox process is strongly inhibited when [H+] increases. Activation parameters were also determined for selected reactions. On the basis of the kinetic result, activation parameters data and oxidized organic products, the mechanism of saccharides oxidation by CrO2+ is proposed to be a direct hydride-ion transfer.
2,5-Diketo-gluconic acid reductase from Corynebacterium glutamicum: Characterization of stability, catalytic properties and inhibition mechanism for use in vitamin C synthesis
Kaswurm, Vanja,Pacher, Claudia,Kulbe, Klaus Dieter,Ludwig, Roland
, p. 2012 - 2019 (2013/02/25)
2,5-Diketo-d-gluconic acid (2,5-DKG) reductase is an NADPH-dependent, monomeric aldo-keto reductase (AKR) which catalyzes the reduction of 2,5-DKG to 2-keto-l-gulonic acid (2-KLG) - the immediate precursor of vitamin C. The reaction catalyzed by 2,5-DKG reductase is attractive to bypass several chemical steps and produce vitamin C biocatalytically. In a screening of 22 bacterial strains, nine 2,5-DKG reductase producing bacterial strains were found. The gene of Corynebacterium glutamicum 2,5-DKG reductase was cloned and overexpressed in Escherichia coli. By batch fermentation 409 mg L-1 of 2,5-DKG reductase with a C-terminal His6-tag were obtained. The purified 2,5-DKG reductase was characterized in detail. The enzyme is most active in a pH range from 5.0 to 8.0 and its stability is high at temperatures below 35 °C. Catalytic constants for 2,5-DKG and NADPH were determined and a weak inhibition by the product 2-KLG was found. 2,5-DKG reductase activity is strongly inhibited by the common process ions Mg2+, Ca2+, SO43- and Cl-, which suggests that these should be avoided in the process. The inhibition mechanism for Cl- was elucidated. It is a competitive inhibitor with respect to NADPH and a noncompetitive inhibitior with respect to 2,5-DKG.
Monosaccharide-H2O2 reactions as a source of glycolate and their stimulation by hydroxyl radicals
Maksimovi?, Vuk,Mojovi?, Milo?,Vu?ini?, ?eljko
, p. 2360 - 2369 (2007/10/03)
An analysis of the H2O2-induced breakdown and transformation of different keto-monosaccharides at physiological concentrations reveals that glycolate and other short-chained carbohydrates and organic acids are produced. Depletion of monosaccharides and glycolate synthesis occurs at increased rates as the length of the carbohydrate chain is decreased, and is significantly increased in the presence of trace amounts of Fe2+ ions (10 μM). Rates of monosaccharide depletion (initial concentration of 3 mM) observed were up to 1.55 mmol h-1 in the case of fructose, and 2.59 mmol h-1 in the case of dihydroxyacetone, depending upon pH, H2O2 concentration, temperature and the presence or absence of catalytic amounts of Fe2+. Glycolate was produced by dihydroxyacetone cleavage at rates up to 0.45 mmol h-1 in the absence, and up to 1.88 mmol h-1 in the presence of Fe2+ ions (pH 8). Besides glycolate, other sugars (ribose, glyceraldehyde, glucose), glucitol (sorbitol) and organic acids (formic and 2-oxogluconic acid) were produced in such H2O2-induced reactions with fructose or dihydroxyacetone. EPR measurements demonstrated the participation of the {radical dot}OH radical, especially at higher pH. Presence of metal ions at higher pH values, resulting in increased glycolate synthesis, was accompanied by enhanced hydroxyl radical generation. Observed changes in intensity of DEPMPO-OH signals recorded from dihydroxyacetone and fructose reactions demonstrate a strong correlation with changes in glycolate yield, suggesting that {radical dot}OH radical formation enhances glycolate synthesis. The results presented suggest that different mechanisms are responsible for the cleavage or other reactions (isomerisation, auto- or free-radical-mediated oxidation) of keto-monosaccharides depending of experimental conditions.
METHOD FOR SELECTIVE CARBOHYDRATE OXIDATION USING SUPPORTED GOLD CATALYSTS
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Page/Page column 40-42, (2010/02/09)
The invention relates to a method for the selective oxidation of a carbohydrate in the presence of a gold catalyst comprising gold particles distributed in a nanodispersed manner on a metal oxide support, and to a method for the selective oxidation of an oligosaccharide in the presence of a gold catalyst comprising gold particles distributed in a nanodispersed manner on a carbon or metal oxide support. The invention also relates to aldonic acid oxidation products produced using said method.
METHOD FOR EXTRACTING 2-KETONE-L-GULONIC ACID FROM A POLAR, PREFERABLY AQUEOUS SOLVENT
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Page/Page column 17, (2008/06/13)
The invention relates to a method for extracting 2-ketone-L-gulonic acids from a polar, preferably aqueous solvent, preferably from a solvent which contains a mixture of ascorbic acid and 2-ketone-L-gulonic acid, by means of liquid-liquid extraction with the aid of an extraction agent which contains a tertiary amine and a polar organic diluent. Preferably, the inventive method also comprises steps for retro-extracting the 2-ketone-L-gulonic acid and for returning the extraction agent. The invention also relates to a method for producing ascorbic acid from 2-ketone-L-gulonic acid and for isolating the thus produced ascorbic acid.
Non-linear kinetics and mechanism of fructose and bromate reaction in acidic medium
Rastogi,Chand, Prem
, p. 1027 - 1030 (2007/10/03)
Reaction between fructose [F] and bromate (BrO3-) is an important component of the F+Ce4++BrO3-+H2SO4 oscillatory reaction. Kinetics of this reaction has been experimentally investigated. A reaction mechanism has been proposed which is supported by computer simulation.
Platinum-containing hyper-cross-linked polystyrene as a modifier-free selective catalyst for L-sorbose oxidation
Sidorov,Volkov,Davankov,Tsyurupa,Valetsky,Bronstein,Karlinsey,Zwanziger,Matveeva,Sulman,Lakina,Wilder,Spontak
, p. 10502 - 10510 (2007/10/03)
Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by Hsub
