Uric acid, structure

Birds excrete nitrogen as uric acid Uric acid is a purine having the molecular formula C5H4N4O3 it has no C—H bonds Write a structural formula for uric acid... 

The name 5-azaorotic acid should be given to allantoxanic (oxonic) acid but it is not yet commonly used. The elucidation of the correct structure of this compound was closely linked to the solution of the course of oxidation of uric acid mentioned earlier. 

Works on the oxidation of uric acid has unequivocally established the triazine structure > ° (9) of oxonic acid. This is further confirmed by the straightforward synthesis described by Piskala and Gut. ° The reaction of biuret (11) with potassium ethyloxalate yielded a potassium salt (24), that with ethyl oxamate, the amide of oxonic acid (25). Both these compounds were converted to 5-azauracil. An analogous reaction with diethyloxalate which should produce an ester of oxonic acid resulted in a mixture of urethane and parabanic acid, however. 

The deoxyuric acids were early formulated with a cyclic triple bond (138) but recent chemical e ddcnce and ultraviolet spectral data have led to their reformulation as 139 or 140. Although the results of the early investigations of the structure of uric acid using chemical methods were interpreted in favor of structure 141i5s-i6g structure was considered to be supported by its ultraviolet spec-... 

Unsaturation, degree of. 174 Upfield, (NMR), 445 Uracil, structure of, 1101 Urea, from ammonium cyanate, 2 Urethane, 1214 Uric acid, pKa of, 778... 

Xanthine dehydrogenase that mediates the conversion of hypoxanthine into xanthine and uric acid has been studied extensively since it is readily available from cow s milk. It has also been studied (Leimkiihler et al. 2004) in the anaerobic phototroph Rhodobacter capsulatus, and the crystal structures of both enzymes have been solved. Xanthine dehydrogenase is a complex flavoprotein containing Mo, FAD, and [2Fe-2S] redox centers, and the reactions may be rationalized (Hille and Sprecher 1987) ... 

Many compounds of biomedical interest, both of endogenous and exogenous origin, are heterocyclic in structure. Many of these compounds are electroactive at potentials useful for LCEC analysis. Methods for the determination of both ascorbic acid and uric acid were developed in the early days of LCEC. The important enzyme... 

Table 2. Structures of proposed primary products or intermediates formed on oxidation of uric acid along with the major products of the oxidations...

The amino groups are replaced with oxygen. Although here a biochemical reaction, the same can be achieved under acid-catalysed hydrolytic conditions, and resembles the nucleophilic substitution on pyrimidines (see Section 11.6.1). The first-formed hydroxy derivative would then tautomerize to the carbonyl structure. In the case of guanine, the product is xanthine, whereas adenine leads to hypoxanthine. The latter compound is also converted into xanthine by an oxidizing enzyme, xanthine oxidase. This enzyme also oxidizes xanthine at C-8, giving uric acid. 

Urea-hydrogen peroxide (UHP) crystal structure, 98, 99 disilazane reactions, 814-15 transition metal peroxides, 1083, 1089-90, 1099, 1103, 1113 Uric acid... 

The uricosuric drugs (or urate diuretics) are anions that are somewhat similar to urate in structure therefore, they can compete with uric acid for transport sites. Small doses of uricosuric agents will actually decrease the total excretion of urate by inhibiting its tubular secretion. The quantitative importance of the secretory... 

The free acid — a trimer of isocyanic acid — probably has the structure (IV). Cyan-uric acids are of some importance as sources of initiating materials (cyanuric azide, for example, p. 194). 

Our interpretation resembles somewhat that proposed by Roseman and Jencks (2) in order to describe the behavior of nonelectrolytes like uric acid in aqueous binary mixtures, though these authors seem to refuse to consider the respective magnitude of entropy and enthalpy as indications of structural effects, as we have done. 

---