Degradation, of aldonic acids

G. Hourdin, The catalysis of the Ruff oxidative degradation of aldonic acids by titanium-containing zeolites, Catal. Lett., 69 (2000) 241-244. 

There are some reactions that use Fe(III) and H202 such as the Ruff degradation of aldonic acids [reaction (91) Moody 1964]. Here, Fe3+ only acts as a catalyst and free radicals seem not to be involved in this reaction. 

Two useful preparations of lower sugars by degradation of aldonic acids are discussed in the following Chapter. These are the traditional oxidation of salts of aldonic acids with hydrogen peroxide in the presence of ferric acetate (Ruff degradation) and the related oxidation of aldonic acids by hypochlorite, which was developed by Whistler and Schweiger.79... 

The well-known Ruff degradation of aldonic acids to aldoses with one less carbon was first applied with bromine as the oxidant. Calcium D-gluconate was treated with an excess of bromine at 20° for ten hours the acidity of the solution was kept low with lead carbonate. The filtrate was processed and D-arabinose was obtained in small yield as the oxime. However, Ruff found that the effect of hydrogen peroxide was much better and abandoned the use of bromine. Fenton noted the same effect in the oxidation of tartaric acid to dihydroxymaleic acid the action of oxygen was more effective than that of the halogens. It was assumed that a keto aldonic acid was the intermediate in the degradation of the aldonic acid to the new aldose, and the apparent stability of the keto acids to further oxidation by bromine may be the reason for the low yields with this oxidant. 

By use of hydroxy- and keto-acids as model compounds, the RuflF degradation of aldonic acids with hydrogen peroxide and iron(iii) has been examined, and the pathway illustrated in Scheme 1 proposed. A remaining difficulty. 

The principal value of oxidations with hydrogen peroxide is for the degradation of aldonic acids to sugars with one less carbon atom ferric sulfate is used as a catalyst (see p. 118). It is noteworthy that although ferric salts catalyze this reaction, ferrous salts are used for sugars and ferric salts are not effective. 

Pyruvate-dependent lyases serve catabolic functions in vivo in the degradation of sialic acids and KDO (2-keto-3-deoxy-manno-octosonate), and in that of 2-keto-3-deoxy aldonic acid intermediates from hexose or pentose catabolism. 

Deulofeu, Venancio, The Acylated Nitriles of Aldonic Acids and Their Degradation, IV, 119-151... 

Apart from the general procedures that have been described, nitriles of aldonic acids are capable of other reactions that also lead to degradations. 

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). 

In vivo, pyruvate lyases perform a catabolic function. The synthetically most interesting types are those involved in the degradation of sialic acids or the structurally related octulosonic acid KDO, which are higher sugars typically found in mammalian or bacterial glycoconjugates [62-64], respectively. Also, hexose or pentose catabolism may proceed via pyruvate cleavage from intermediate 2-keto-3-deoxy derivatives which result from dehydration of the corresponding aldonic acids. Since these aldol additions are freely reversible, the often unfavourable equilibrium constants require that reactions in the direction of synthesis have to be driven by an excess of one of the components, preferably pyruvate for economic reasons, in order to achieve a satisfactory conversion. 

Dahlia tubers, inulin from, II, 254 Dambonitol, III, 46 Damson gum, I, 343 IV, 246, 247 structure of, IV, 253 blood group activity of, IV, 50, 52 Deamination, mechanism of, II, 62 Degradation, of acylated nitriles of al-donic acids, IV, 119-151 of aldonic acids, III, 149 of aldose sugars, I, 254 enzymatic, of starch and glycogen, III, 251-310... 

Deulofeu, Venancio, The Acylated Nitriles of Aldonic Acids and Their Degradation, 4, 119-151 Dimler, R. J., 1,6-Anhydrohexofuranoses, A New Class of Hexosans, 7, 37-52 Doudoroff, M. See Hassid, W. Z. Dubach, P. See Mehta, N. C. 

Ruff-Fenton degradation. Shortening of the carbon chain of sugars by the oxidation of aldonic acids (as calcium salts) with hydrogen peroxide and ferric salts. 

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