- Insights into the biological redox chemistry of 2′-deoxyadenosine 5′-monophosphate by electrochemical techniques
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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.
- Goyal, Rajendra N.,Dhawan, Aikta
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- Facile synthesis of 1,2,3-tricarbonyls from 1,3-dicarbonyls mediated by cerium(IV) ammonium nitrate
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A mild and efficient protocol for the synthesis of vicinal tricarbonyl compounds from β-dicarbonyls in a single step using cerium(IV) ammonium nitrate as a catalytic oxidant is described. Ease of execution, wide substrate scope and the suitability for the synthesis of commercially important compounds like ninhydrin, alloxan and oxoline make this reaction particularly noteworthy.
- Sivan, Akhil,Deepthi, Ani
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supporting information
p. 1890 - 1893
(2014/03/21)
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- On-line electrochemistry/thermospray/tandem mass spectrometry as a new approach to the study of redox reactions: the oxidation of uric acid.
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The electrochemical oxidation pathway of uric acid was determined by on-line electrochemistry/thermospray/tandem mass spectrometry. Intermediates and products formed as a result of electrooxidation were monitored as the electrode potential was varied. Several reaction intermediates have been identified and characterized by tandem mass spectrometry. The tandem mass spectrometric results provide convincing evidence that the primary intermediate produced during the electrooxidation of uric acid has a quinonoid diimine structure. The results indicate that once formed via electrooxidation, the primary intermediate can follow three distinct reaction pathways to produce the identified final products. The final electrochemical oxidation products observed in these studies were urea, CO2, alloxan, alloxan monohydrate, allantoin, 5-hydroxyhydantoin-5-carboxamide, and parabanic acid. The solution reactions that follow the initial electron transfer at the electrode are affected by the vaporizer tip temperature of the thermospray probe. In particular, it was found that at different tip temperatures either hydrolysis or ammonolysis reactions of the initial electrochemical oxidation products can occur. Most importantly, the results show that the on-line combination of electrochemistry with thermospray/tandem mass spectrometry provides otherwise difficult to obtain information about redox and associated chemical reactions of biological molecules such as the structure of reaction intermediates and products, as well as providing insight into reaction pathways.
- Volk,Yost,Brajter-Toth
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p. 1709 - 1717
(2007/10/02)
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- The sonolysis of uracil
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The sonolysis of uracil (1) has been studied at 630 kHz in the presence of air, oxygen, nitrogen and argon.The degradation products were identified by gc-ms analysis.Under aerated conditions the following products were found: uracil glycols (7), isobarbituric acid (8), N-formyl-N'-glyoxylurea (6), 5-hydroxyhydantoin (9), dialuric acid (10), alloxan monohydrate (12), parabanic acid (13), and oxaluric acid (14).In deaerated solutions 6, 13, and 14 were not observed but either 6-hydroxy-5,6-dihydrouracil (17) or its isomer (18) were detected in addition to 7, 8, 9, 10, and 12.The observed products have been used to develop a possible mechanism for the sonolytic degradation and the results are similar to those obtained in radiolysis.The sonolytic degradation of 5-bromouracil (19) is also reported: the products observed were 5-bromobarbituric acid (20), 12, 13, 14, and 9 and these can be rationalized by a similar mechanism scheme.
- Yu, Tain-Jen,Sutherland, Ronald G.,Verrall, Ronald E.
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p. 1909 - 1915
(2007/10/02)
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- Reduction of Vicinal Tricarbonyl Compounds by Reduced Nicotinamide Adenine Dinucleotide Model and Electron-Transport Systems
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The reduction of vicinal tricarbonyl compounds such as alloxan (A) and ninhydrin (NY) with 1-benzyl-1,4-dihydronicotinamide (BNAH; NADH model) was investigated.In the reduction of A with BNAH, the radical anion (A-.Py+) of A as the 1-benzyl-3-carbamoylpyridinium salt and the dialuric acid (D) was obtained by one-electron and two-electron reduction,respectively.Similarly,hydrindantin (HDT) and 2-hydroxy-1,3-indandione (HID) were also afforded in the reduction of NY with BNAH.Further,the reductions of alloxantin (AT) and HDT with BNAH were performed to give D and HID,respectively.The reduction of lipoic acid (LA) and viologens (V2+) with BNAH, which could not be reduced without A or NY, proceeded smoothly in their presence,and they proved to be useful as mediators for catalytic reduction of LA and V2+.
- Endo, Takeshi,Okawara, Makoto
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p. 2663 - 2666
(2007/10/02)
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