33501-14-3Relevant academic research and scientific papers
The reactions of thymine and thymidine with ozone
Flyunt, Roman,Theruvathu, Jacob A.,Leitzke, Achim,Von Sonntag, Clemens
, p. 1572 - 1582 (2002)
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.
Insights into the biological redox chemistry of 2′-deoxyadenosine 5′-monophosphate by electrochemical techniques
Goyal, Rajendra N.,Dhawan, Aikta
, p. 1944 - 1952 (2007/10/03)
The electrochemical oxidation of 2′-deoxyadenosine 5′-monophosphate at a pyrolytic graphite electrode (PGE) was studied in the pH range 2.65-10.03 and was found to proceed in a single well-defined oxidation peak, Ia, over the entire pH range. The cyclic voltammetric behavior indicated the pH dependence of the oxidation pathway. The kinetic studies of the UV-absorbing intermediate generated during electrooxidation were followed spectrophotometrically, and decay occurred in a pseudo first-order reaction having k values in the range (0.595-0.986) × 10-3 s-1 over the entire pH range studied. Coulometric studies indicated that the process of the oxidative pathway involved n values as 5.0 ± 0.5 in the acidic range (pH 3.37) and 4.0 ± 0.5 at physiological pH 7.22. The products of electrooxidation were characterized by GC-MS and on the basis of electrochemical, spectrochemical, and product analysis; a plausible redox mechanism is suggested.
