Oxidation of aldoses

Derivatives of aldoses in which the terminal aldehyde function is oxidized to a car boxylic acid are called aldonic acids Aldonic acids are named by replacing the ose ending of the aldose by omc acid Oxidation of aldoses with bromine is the most com monly used method for the preparation of aldonic acids and involves the furanose or pyranose form of the carbohydrate... 

Aldaric acid (Section 25 19) Carbohydrate in which car boxyhc acid functions are present at both ends of the chain Aldanc acids are typically prepared by oxidation of aldoses with nitnc acid... 

Other multifunctional hydroxycarboxylic acids are mevalonic and aldonic acids which can be prepared for specialized uses as aldol reaction products (mevalonic acid [150-97-0] (13)) and mild oxidation of aldoses (aldonic acids). 

Enediol formation is also rate limiting in the oxidation of aldoses and ketoses by alkaline ferricyanide , the rate expression being... 

Technically important is the dimethoxylation of furan and its derivatives to form 2,5-dimethoxy-2,5-dihydrofuran (Eq. (13)) and the oxidation of aldoses to... 

Scheme V. Free radical oxidation of aldoses (Pathway I)...

Some of the key reactions in carbohydrate chemistry involve oxidation of aldoses to carboxylic acids. You will encounter some of these if you work Exercise 20-1. There is a simple nomenclature system for these acids. In abbreviated notation, the products of oxidation at Cl, C6, or both are called ... 

Nitric acid oxidation of aldoses converts them to aldaric acids. The same D-aldoses found to yield optically inactive alditols in part (a) yield optically inactive aldaric acids. 

Oxidation of aldoses by hypoiodite can also be used for preparative purposes.7 Other types of halogen oxidants, especially A-halo compounds, are useful. For example, A -bromocarbamide was recommended by Kiss8 as a selective and convenient reagent for oxidizing benzylated sugars to their corresponding aldonolactones in yields exceeding 90%. Another example is the use of A-iodosuccinimide and tetrabutylammonium iodide.9... 

Oxidation of aldoses can be achieved with other oxidants. The increased use of D-ribonolactone as a chiral intermediate in organic synthesis10,11 has encouraged the search for new oxidants. 

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... 

H. L. Frush and H. L. Isbell, Aldonic acids. By electrolytic oxidation of aldoses calcium D-gluconate dihydrate, Methods Carbohydr. Chem., 2 (1963) 14-15. 

P. C. C. Smits, B. F. M. Kuster, K. Van der Wiele, and H. S. Van der Baan, The selective oxidation of aldoses and aldonic acids to 2-ketoaldonic acids with lead-modified platinum-on-carbon catalysts, Carbohydr. Res., 153 (1986) 227-235. 

The ruthenium-catalyzed oxidation of aldoses by NBS under acidic46 and basic47 conditions have been investigated. The order of reactivity of some pentoses and hexoses has been determined for their oxidation by NBS in aqueous acidic media containing Hg(II) acetate. A mechanism for the reaction has been suggested on the basis of kinetic measurements.48... 

Manganese(III) has been employed for the oxidation of aldoses, and a general mechanism for the oxidation has been proposed.167 The oxidation of hexoses, pentoses, hexitols, and pentitols by Mn(III), as well as by other cations, was proposed to proceed via a free-radical mechanism,168 as shown in Scheme 26. Oxidation of alditols produces the corresponding aldoses, which are further oxidized in the presence of an excess of oxidant to the lower monosaccharides and thence to formaldehyde, formic acid, and even carbon dioxide. The kinetics for the oxidation of aldoses and ketoses by Mn(III) in sulfuric acid medium have been reported.169... 

Oxidation of aldoses and ketoses with ferricyanide under alkaline conditions involves the 1,2-enediol as an intermediate. Such an oxidation... 

In perchloric acid, hexoses and pentoses are oxidized by Ce(IV) via formation of two complex intermediates. The first is partly oxidized following Michaelis-Menten kinetics and partly dissociated to the second, which is oxidized more slowly than the former.180 The first step in the oxidation of aldoses by Tl(III) in the same medium involves the C-l-C-2 cleavage of the aldehydo form of the sugar. Thus, D-glucose gives D-arabinose and formic acid. With an excess of oxidant the final product is carbon dioxide.181 In the presence of a catalytic amount of sulfuric acid in acetic acid, Tl(III) oxidizes maltose and lactose to the corresponding disaccharide aldonic acids. The reaction showed activation enthalpies and enthropies characteristic of second-order reactions.182... 

Many other cations of transition metals have been employed for the oxidation of sugars. For example, the oxidation of aldoses by hexachloroiridate(IV)183,184 and tetrachloroaurate(III)183,185 in hydrochloric acid led to the corresponding aldonic acids or aldonolactones. The observed... 

I. Kistayya, M. S. Reddy, and S. Kandlikar, Kinetics of Ru(III) catalyzed oxidation of aldoses by V-bromosuccinimide in aqueous acetic acid, Indian J. Chem., Sect. A, 25 (1986) 905-907 Chem. Abstr., 106 (1987) 176755. 

H. S. Isbell, H. L. Frush, and E. T. Martin, Reactions of carbohydrates with hydroperoxides. Part I. Oxidation of aldoses with sodium peroxide, Carbohydr. Res., 26 (1973) 287-295. 

V. M. Parikh and J. K. N. Jones, Oxidation of sugars with ruthenium dioxide-sodium periodate a simple method for the preparation of substituted keto sugars, Can. J. Chem., 43 (1965) 3452-3453 compare R. H. Hall and K. Bischofberger, The preparation of aldonolactones and lactols by oxidation of aldoses with ruthenium(VIII) oxide, Carbohydr. Res., 65 (1978) 139-143. 

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