Degradation of aldoses

RUFF - FENTON Degradation Oxidative degradation of aldoses via a-hydroxy acids to lower chain aldoses. 

Reacts with aldoses to yield oximes as the first step in the Wohl degradation of aldoses (Section 25.6). 

Degradation of aldoses. It has been used in a Wohl-type degradation in which an aldose oxime is treated with 2,4-dinitrofiuorobenzene to form the oxime aryl ether, which decomposes to the next lower aldose, 2,4-dinitrophenoI, and hydrogen cyanide. ... 

USE Reagent for labeling a terminal amino acid group in modified Wohl degradations of aldoses. As hapten, Caution,- Vesicant. For proper handling see J. S, Thompson, O. P. Edmunds, Ann. Occup. Hyg, 23. 27 (1980). 

Under such conditions secondary alcohols rarely afford homogeneous products, as the aldehydes expected as primary products too readily undergo further reactions. Exceptionally, a preparatively useful application has been found in the degradation of aldose diethyl dithioacetals these are oxidized by organic peracids or by hydrogen peroxide in the presence of ammonium molybdate to the disulfones which are cleaved at secondary alcohol groups by dilute ammonia solution.78,79 This method has been applied to acetyl-... 

WOHL - WEYGAND Aldose degradation Degradation of sugar oximes via cyanohydrins by means of an acid chloride/pyridine (Wohl) or of... 

Aldoses and aldosides, cyclic acetals of, 20, 219-302 Alkaline degradation, of polysaccharides, 13, 289-329 Altrose,... 

Brigl and coworkers9 discovered the first example showing that the formation of aldose amides is not restricted to the degradation of acylated nitriles of aldonic acids. By ammonolysis of 2,3,4,5,6-penta-O-benzoyl-aldehydo-n-glucose (16), they obtained l,l-bis(benz-amido)-l-deoxy-D-glucitol (17). 

Consideration of reasonable mechanisms for producing formic acid from an aldose led to the hypothesis that the sugar forms an addition product with the hydroperoxide anion, comparable with an aldehyde sulfite or the addition product of aldoses with chlorous acid (52). The intermediate product (12) could decompose by a free-radical or an ionic mechanism. In the absence of a free-radical catalyst, the ionic mechanism of Scheme VIII seems probable. By either mechanism the products are formic acid and the next lower sugar. The lower sugar then repeats the process, with the result that the aldose is degraded stepwise to formic acid. Addition of the hydroperoxide anion to the carbonyl carbon is in accord with its strong nucleophilic character (53) and with certain reaction mechanisms suggested in the literature (54) for related substances. 

Methods for the chemical synthesis of glycuronic acids include (i) reduction of the monolactones of aldaric acids, (ii) oxidation of the primary alcoholic group of aldose derivatives, (iii) oxidative degradation procedures, (iv) chain-extension reactions on dialdoses, and (v) epimerization reactions. 

Ferric ion catalyzes the formation of the hydroperoxyl radical, according to Eq. (35) such a radical appears to constitute the oxidant in the Ruff method of degrading aldonic acids to the next lower aldoses. A number of examples of the use of this reagent in the laboratory are given in a review article by Moody.108 The hydroperoxyl radical, which is not so effective an oxidant as the hydroxyl radical, does not attack aliphatic alcohols accordingly, a substantial yield (about 50%) of the aldose is obtained from the higher aldonic acid. In the presence of an excess of hydrogen peroxide, however, the accumulation of ferrous ions in solution catalyzes the production of hydroxyl radicals and lowers the yield of aldose [see Eq. (36)]. 

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