Oxidation of D-xylose

An efficient double oxidation of D-xylose to D-gf/ycero-aldopentos-2,3-diulose (2,3-diketo-D-xylose, 45) has been achieved (80% yield) using pyranose dehydrogenase from the mushroom Agaricus bisporus (Scheme 9). The gram scale 2 -deoxygenation of ATP has been achieved using a recombinant ribonucleoside triphosphate reductase from Lactobacillus leichmannii ... 

C, have been determined. The kinetics and mechanism of the oxidation of D-xylose, L-arablnose, and D-galactose by acidic aqueous chromium peroxydichromate. In hlch HCrO is the primary oxidant, have been determined. 

Kinetics of the Rh(III)-catalysed oxidation of D-xylose and L-sorbose with N-bromo-acetamide, " ofpalladium(II)-catalysed oxidation of methylamine and ethylamine by IV-bromosuccinimide (NBS), and of alcohols by A -bromoisonicotinamide have been determined and suitable mechanisms have been suggested. Catalytic role of cetyltrimethylammonium bromide in the oxidation of galactose and acetaldehyde by IV-bromophthalimide (NBP) has been examined. Various activation and kinetic parameters have been evaluated and a mechanism has been proposed. Kinetic and activation parameters of the oxidation of glutamic acid by NBP have been determined and a mechanism has been suggested. The kinetics of oxidation of meta- and para-substituted piperidin-4-ones with and of oxidation of propionaldehyde... 

D-xylopyranose units. This structural concept is substantiated by estimation of the formic acid obtained when the xylan is oxidized by periodate ions. On hydrolysis of the fully oxidized xylan there is obtained a small amount of D-xylose which presumably occupied the branch points in the polysaccharide and consequently was protected from periodate oxidation by possessing no adjacent free hydroxyl groups. 

A. Tri-O-acetyl-D-xylono-l,4-lactone 2. a) Bromine oxidation. A 250-mL, threenecked, round-bottomed reaction flask equipped with a magnetic stirrer, thermometer, and an addition funnel is charged with 30.0 g (0.20 mol) of D-xylose and 80 mL of water. After the clear aqueous solution is cooled with an ice-water bath, 34.0 g 0.23 mol) of potassium carbonate is added in portions, keeping the temperature below 20°C. After the mixture is cooled to below 5°C, 12 mL (0.22 mol) of bromine is added dropwise over 90 min, keeping the temperature of the reaction mixture below 10°C (Note 1). The orange solution is stirred at that temperature for 30 min, then at room temperature overnight. The reaction is quenched by careful addition of 88% formic acid (2.5 mL) to afford a colorless solution (Note 2). The solution is concentrated at 50°C on a rotary evaporator and 20 mL of acetic acid is added. The mixture is Concentrated again at 50°C to remove any residual water (Note 3). 

The principle of the reactions between aldonolactones and HBr-HOAc is illustrated in Scheme 1 (entries I and II), and the mono- and di-bromodeoxylactones prepared in this way are listed in Table 1. The 2-bromo-2-deoxy-D-erythrono-and D-threonolactone can be prepared analogously to the L-isomers [11] from the salts of D-threonic and o-erythronic acid [ 12], respectively. The former can be prepared by oxidative degradation of D-xylose following an analogous procedure described by Humphlett [13]. 

A more-direct method of preparation is oxidation of aldoses, and optimal yields are afforded by the action of cupric acetate in methanol or ethanol.417 This method is suitable for large-scale preparation of intermediates however, a pure product is obtained only by chromatographic separation from the unreacted sugar byproducts. The synthesis of D-eryt/wo-pentos-2-ulose and its D-threo isomer by oxidation of D-arabinose and D-xylose, respectively, with cupric acetate followed by anion-exchange chromatography has been reported.418 The only product obtained by oxidation of D-glucose with sodium 2-anthraquinonesulfonate in alkaline... 

A purified D-glucose dehydrogenase, isolated from animal liver, catalyzes the oxidation of D-glucose to D-gluconic acid.202 A coenzyme (either nicotinamide adenine dinucleotide or its 2 -phosphate) is necessary for the oxidation. The reaction is reversible, and is specific for /J-D-glucopyranose it does not proceed with the a-D anomer, and it occurs only slowly with D-xylose. 

Incubation of D-xylose with an aqueous solution of bovine lens protein gave both xylitol and xylonic acid. Studies of the reaction under a variety of conditions suggest that both the reduction and oxidation reactions are protein (possibly enzyme) catalyzed and appear to be unique to lens... 

The kinetics of the oxidation of D-galactose and D-xylose by an alkaline solution of sodium metaperiodate has been studied, using ruthenate ion (Ru042 ) as a catalyst.329... 

The ruthenate ion-catalysed oxidation of D-galactose and D-xylose by alkaline periodate in an alkaline solution showed a zero-order dependence on reducing sugar and a first-order dependence on ruthenate ion. The first-order dependence of the reaction on periodate and alkali at their low concentrations tends to zero order at higher concentrations. A mechanism consistent with the kinetics has been proposed.138 The kinetics of the periodate oxidation of p-bromoanilinc139 and 4-chloro-2-methylaniline140 have been determined and interpreted. 

The barium salt from the methanol-hypoiodite oxidation of 7.5 g. (0.05 mole) of D-xylose was suspended in a small amount of water and decomposed with sulfuric acid. The barium sulfate was filtered and the solution concentrated to a sirup at reduced pressure. To the sirup dissolved in a mixture of 25 ml. of ethanol and 125 ml. of butanol, 4.6 g. (0.025 mole) of o-phenylenediamine dihydrochloride and 2.4 g. (0.022... 

Because A is oxidized to an optically inactive aldaric acid, the possible structures are D-ribose and D-xylose. Chain extension of D-xylose, however, produces two hexoses that, when oxidized, yield optically active aldaric acids. 

The number of ml. of 0.1 iV iodine minus the number of ml. of 0.1 N thiosulfate, and the number of ml. of 0.1 N sodium hydroxide minus the number of ml. of 0.1 N hydrochloric acid give the respective quantities of 0.1 A iodine and 0.1 JV sodium hydroxide used in the oxidation of the sugar. One millimole of the sugar (0.15 g. of D-xylose) requires for oxidation 20 ml. of 0.1 N iodine and 30 ml. of 0.1 N sodium hydroxide (reaction 14, page 157). Either iodine or alkali consumed, or both as checks, may be used to calculate the amount of aldose present. 

The oxidation of D-glucose to D-gluconic acid is also readily carried out by use of a platinum-on-carbon catalyst (a substantially more-active catalyst) in the presence of an equivalent of alkali. With the aid of the same catalysts, n-galactose, D-mannose, D-xylose, and L-arabinose can be converted to the corresponding aldonic acids. By this method, the pentoses are oxidized more rapidly than the hexoses. A reaction time of only 45 minutes is required at 22°, whereas the oxidation of D-glucose is complete only after five hours. 

Preparation. D-r/treo-Pentulose may be synthesized by isomerization of d-xylose in hot pyridine. Better yields are obtained by the oxidation of D-arabinitol employing Acetobacter xylinum 60... 

The kinetics of chromic acid oxidation of D-galactose, D-mannose, L-arabinose, and D-xylose in perchloric acid media have been measured. The reaction was found to be first-order with respect to Cr and to [aldose] but showed a complex dependence on The activation parameters were... 

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