3-Ketoaldonic acid

Oxo carboxylic acids formally derived from aldonic acids by replacement of a secondary CHOH group by a carbonyl group are called ketoaldonic acids (see 2-Carb-21). 

The parent that includes the functional group most preferred by general principles of organic nomenclature [13,14], If there is a choice, it is made on the basis of the greatest number of occurrences of the most preferred functional group. Thus aldaric acid > uronic acid/ketoaldonic acid/aldonic acid > dialdose > ketoal-dose/aldose > diketose > ketose. 

Names of individual ketoaldonic acids are formed by replacing the ending -ulose of the corresponding ketose by -ulosonic acid , preceded by the locant of the ketonic carbonyl group. The anion takes the ending -ulosonate . The numbering starts at the carboxy group. 

In glycosides derived from ketoaldonic acids, the ending is -ulosidonic acid , with appropriate ring-size infix, e.g. -ulopyranosidonic acid . 

Keratan 6-sulfate, 383-384,427 Ketals, nomenclature, 123-124 Ketoaldonic acids, 51,106-107 Ketoaldoses, 51,79-80 Ketoses... 

Two biologically important ketoaldonic acids should be mentioned here. N-Acetylneuraminic acid (5-acetamido-3,5-dideoxy-D-gh/cero-D-gaiocto-nonulosonic acid) is homomorphous with 3-deoxy-g(uco(and monno)-heptulose, and therefore, in solution, would be expected to be overwhelmingly in the / -D -pyranose form (14). Actually, although the... 

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. 

D-glucose (aldose) aldonic acid 2-ketoaldonic acid D-arabinose... 

Aldonic and ketoaldonic acids may be difficult to separate. Norris and Campbell separated ketogluconic acid from gluconic acid by preparing the phenylhydrazone of the keto acid, which is then easily separable from gluconic acid. A methanol-ethanol-water solvent mixture was used.64 Another useful solvent developer is 1-butanol-formic acid-water.133 Macek and Tadra separated a series of ketoaldonic acids in a number of acidic solvent developers.134 Color reagents which may be used include ammoniacal silver nitrate,94 o-phenylenediamine dihydrochloride,84 and aniline acid oxalate.138 Lactones are detectable with hydroxylamine followed by ferric chloride.128... 

Carbohydrate carboxyl groups are present in natural oligosaccharides as uronic and ketoaldonic acids. These are found in nature as components of heparin (glucuronic and iduronic acid), bacterial lipopolysaccharides (Kdo and sialic acid) and human glycan strucmres (sialic acid Figure 3.5). 

Thus in the Ruff degradation, for example of o-glucose to o-arabinose, the aldose is oxidized electrolytically to the aldonic acid and this on treatment with hydrogen peroxide and ferric acetate affords the 2-ketoaldonic acid (aldosulose), which yields D-arabinose by loss of carbon dioxide. The yield of aldopentose from the aldonic acid... 

Condensation of 2-ketoaldonic acids (ulosonic acids, 729) or their esters with 721 gave the 2-(alditol-l-yl)quinoxalin-3-ones 730 (34CB155 37CB2148 61CB1743 69HCA300) (Scheme 187). 

The synthesis of 2-ketoaldonic acids continues to attract considerable attention. The Wittlg reagent (16) can be used for the synthesis of 3-deojqr-D-arabino-2-heptulosonlc acid as indicated in Scheme 5 reagent (16) could also be used in conjunction with a D-mannose derivative to make KDO, but since... 

The postulated dehydrogenation at C giving rise to the ketose resolves the difficulty of effecting an epimerization at C of the expected precursor, D-arabinose-5-phosphate, to form D-ribose-S-phosphate. However, the postulated 3-keto acid has not been isolated nor has any trace of it or its isomers been seen. 3-Ketoaldonic acids have not been isolated as such when synthesized, they are foimd in equilibrium mixtures with their enolic lactones. Of course, it may be postulated that the intermediate... 

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