57609-73-1Relevant articles and documents
The reactions of thymine and thymidine with ozone
Flyunt, Roman,Theruvathu, Jacob A.,Leitzke, Achim,Von Sonntag, Clemens
, p. 1572 - 1582 (2007/10/03)
The ozonolysis of thymine and thymidine has been investigated by a product study complemented by kinetic studies using spectrophotometry, conductometry and stopped-flow with optical and conductometric detection. Material balance has been obtained. Ozonolysis of thymine (k = 3.4 × 104 dm3 mol-1 s-1) leads to the formation of the acidic (pKa = 4) hydroperoxide 1-hydroperoxymethylene-3-(2-oxopropanoyl)urea 5 (～34%), neutral hydroperoxides (possibly mainly 1-hydroperoxyhydroxymethyl-3-(2-oxopropanoyl)urea 6, total ～41%) and H2O2 (25%, with corresponding formation of 1-formyl-5-hydroxy-5-methylhydantoin 11). The organic hydroperoxides decay (～1.1 × 10-3 s-1 at 20°C, 1.3 × 10-4 s-1 at 3°C) releasing formic acid (formation of 5-hydroperoxy-5-methylhydantoin 18) and also to some extent H2O2 (and 11). After 100 min, the formic acid yield is 75%. Upon treatment at high pH, it increases to 100%. Reduction of the organic hydroperoxides with bis(2-hydroxyethyl) sulfide (k = 50 dm3 mol-1 s-1) leads to 11 whose subsequent treatment with base yields 5-hydroxy-5-methylhydantoin 13 in 100% yield. It is suggested that the Criegee ozonide formed upon reaction with ozone at the C(5)-C(6) double bond opens heterolytically in two directions with subsequent opening of the C(5)-C(6) bond. In the preferred route (75%), the positive charge resides at C(6). Deprotonation at N(1) gives rise to 5, while its reaction with water yields 6. Loss of formic acid yields 5-hydroperoxy-5-methylhydantoin 18. Reduction of 5 and 6 with the sulfide yields 11. In the minor route (25%), the positive charge remains at C(5) followed by a reaction with water. The resulting α-hydroxy hydroperoxide rapidly loses H2O2 (formation of 11). In basic solution, singlet dioxygen is formed (8%). The concomitant product, 5,6-dihydroxy-5,6-dihydrothymine has been detected. In the ozonolysis of thymidine, the rapid formation of conductance (k = 0.55 s-1) is due to the release of acetic acid (18%). In this reaction a short-lived hydroperoxide is destroyed. As a consequence of this, 25 s after ozonolysis the total hydroperoxide yield is only ～78% (including 8% H2O2). The products corresponding to acetic acid are suggested to be CO2 and N-(2-deoxy-β-D-erythropentofuranosyl)formylurea 22. A number of organic hydroperoxides have been detected by HPLC by post-column derivatisation with iodide. An acidic hydroperoxide such as 5 in the case of thymine is not among the products. Upon sulfide reduction, the organic hydroperoxides yield mainly (43-50%) N1-(2-deoxy-β-D-erythropentofuranosyl)-5-hydroxy-5- methylhydantoin 23. The reasons for some striking differences in the ozonolyses of thymine and thymidine are discussed.
Oxydation de la thymidine par l'ozone: comparaison avec l'action des radicaux hydroxyles
Girault, I.,Molko, D.,Cadet, J.
, p. 863 - 870 (2007/10/02)
The reaction of the base moiety of the thymidine, one of the pyrimidinyl nucleosides, with ozone was examined.This reaction gives rise to five nucleosides which were isolated and characterised.The comparison with the current knowledge of the hydroxyl radical-mediated oxidations of thymidine, in aerated aqueous solution, shows that the ozone oxidation is specific.Indeed, the identified products obtained by the ozonolysis resulted from the opening of the C5-C6 bond.
Radiation-Induced Degradation of Purine and Pyrimidine 2'-Deoxyribonucleosides in Aqueous KBr Solutions
Cadet, J.,Voituriez, L.,Berger, M.,Myers, L. S., (Jr.)
, p. 1643 - 1651 (2007/10/02)
Steady-state γ-radiolysis of 5E-4 M pyrimidine and purine 2'-deoxyribonucleosides in aqueous solutions saturated with N2, N2O and O2, respectively, have been carried out in the presence of 0.1 M KBr.The main final degradation products have been isolated and characterised by various spectroscopic measurements including 1H and 13C NMR, UV, C.D. and mass spectrometry.The radiation-induced decomposition of thymidine is mostly accounted for by an ionic mechanism involving Br2, the decay product of Br2, as the reactive oxidising specie.On the other hand the degradation of the purine ring of 2'-deoxyadenosine and 2'-deoxyguanosine may be accounted for by the action of Br2 or Br3. - Keywords: 2'-Deoxyribonucleosides, Inorganic Radical, γ-Irradiation, Radical Reactions, Thymidine Oxidation
