Xanthine is a purine base found in all body tissues. Colorless crystals, well soluble in solutions of alkalis and acids, formamide , hot glycerin and poorly soluble in water, ethanol and ether.
| Xanthine | |
|---|---|
 | |
| Are common | |
| Systematic name | 3,7-dihydropurin-2,6-dione |
| Chem. formula | C 5 H 4 N 4 O 2 |
| Physical properties | |
| condition | solid (white powder) |
| Molar mass | 152.11 g / mol |
| Thermal properties | |
| T. melt. | decays |
| Chemical properties | |
| Solubility in water | 1 g / 14.5 L at 16 Β° C 1 g / 1.4 l at 100 Β° C |
| Classification | |
| Reg. CAS number | 69-89-6 |
| PubChem | |
| Reg. EINECS number | |
| Smiles | |
| Inchi | |
| Chebi | |
| ChemSpider | |
Content
History
According to an article by V. A. Yakovlev published in ESB , xanthine was synthesized by Armand Gauthier in 1884 [1] .
Properties
Xanthine is characterized by lactim-lactam tautomerism and in aqueous solutions it exists in tautomeric equilibrium with dihydroxy form (2,6-dihydroxypurin) with a predominance of dioxoform.
The xanthine imidazole cycle is nucleophilene: xanthine is halogenated to form 8-halogenxanthines, azo coupling with diazonium salts also forms 8-azoxanthines, which can then be reduced to 8-aminoxanthine or hydrolyzed to uric acid .
Xanthine exhibits amphoteric properties, protonating with imidazole nitrogen and forming salts with mineral acids (including well-crystallizing perchlorate), and forming salts with metals whose cations replace the acidic hydrogen atoms of the dihydroxy form hydroxyls (for example, insoluble silver salt with Tollens reagent ).
In a neutral medium, xanthine is methylated with dimethyl sulfate at imidazole nitrogen atoms to form a dimethyl derivative of the zwitterionic structure , in an alkaline medium, hydroxy form is deprotonated with the formation of highly nucleophilic anions, and, depending on the pH of the reaction mixture, xanthine is methylated to 3,7-dimethyl-xanthine ( teot ), 1,3-dimethylxanthine ( theophylline ) or 1,3,7-trimethylxanthine ( caffeine ).
Under the action of phosphorus oxychloride, the hydroxyl groups of the xanthine dihydroxy form are replaced by chlorine with the formation of 2,6-dichloroxanthin; under the action of phosphorus pentasulfide in pyridine, only one of the hydroxyls is replaced with the formation of 6-thioxanthin.
Xanthine is reduced by sodium amalgam or zinc in hydrochloric acid to 6-deoxyxanthine; under the action of potassium permanganate in an acidic medium, xanthine is oxidized with the imidazole ring degrading to 2,4,5,6-tetraoxopyrimidine ( alloxane ).
Metabolism and Nature
Xanthine is a product of purine catabolism and is formed as a decay product of guanine under the action of guanine deaminase and during the oxidation of hypoxanthine under the action of xanthine oxidase . Under the action of the same xanthine oxidase, xanthine is further converted to uric acid .
Xanthine derivatives include a variety of stimulants, such as caffeine and theobromine . Abiogenic xanthine (along with uracil) was found in the Murchison meteorite. [2]
Pathology
A rare hereditary disease xanthine oxidase deficiency leads to the accumulation of xanthine in the body and xanthuria (the appearance of xanthine in the urine).
See also
- Xanthine oxidase
Notes
- β Yakovlev V.A. Gauthier, Arman // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
- β Martins, Zita; Oliver Botta, Marilyn L. Fogel Mark A. Sephton, Daniel P. Glavin, Jonathan S. Watson, Jason P. Dworkin, Alan W. Schwartz, Pascale Ehrenfreund. Extraterrestrial nucleobases in the Murchison meteorite (Eng.) // Earth and Planetary Science Letters : journal.