Evidence of self-protonation on the electrodic reduction mechanism of an anti-Helicobacter pylori metronidazole isotere

Cavalcanti, Janesmar C.M.; Oliveira, Natália Velasquez; Moura, Maria Aline Barros Fidelis de; Fruttero, Roberta; Bertinaria, Massimo; Goulart, Marília Oliveira Fonseca

doi:10.1016/j.jelechem.2004.05.007

Cited by 11 publications

(3 citation statements)

References 17 publications

(43 reference statements)

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“…1), which under anaerobic conditions can be reduced to the nitroso, hydroxylamino and amino compounds (Eq. 2-4) [30][31][32]. However, in aprotic media, such as DMF, the radical nitro anion is reduced to the nitro dianion under a more negative potential (Eq.…”

Section: Cyclic Voltammetrymentioning

confidence: 99%

Preliminary research on 1-(4-bromo-2-nitroimidazol-1-yl)-3-[ 18 F]fluoropropan-2-ol as a novel brain hypoxia PET tracer in a rodent model of stroke

Nieto

Delgado²,

Sobrado

et al. 2015

European Journal of Medicinal Chemistry

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Section: Cyclic Voltammetrymentioning

confidence: 99%

Preliminary research on 1-(4-bromo-2-nitroimidazol-1-yl)-3-[ 18 F]fluoropropan-2-ol as a novel brain hypoxia PET tracer in a rodent model of stroke

Nieto

Delgado²,

Sobrado

et al. 2015

European Journal of Medicinal Chemistry

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“…Since 1a is a salt formed by a heterocyclic anion and an amino acid, it can be assumed that the transfer of the first electron at the potentials of the first stage is accompanied by rapid protonation of the formed ER product by the initial depolarizer—so-called self-protonation [ 48 , 49 ]. The amino acid l-arginine, which is part of compound 1a , is a good proton donor.…”

Section: Resultsmentioning

confidence: 99%

Redox Conversions of 5-Methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4triazolo[1,5-a]pyrimidinide L-Arginine Monohydrate as a Promising Antiviral Drug

et al. 2021

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This article presents the results of a study of electrochemical transformations in aqueous and aprotic media of 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidinide l-arginine monohydrate (1a, Triazid) obtained by electrochemical methods and ESR spectroscopy. The effect of pH on the current and the reduction potential of 1a in an aqueous Britton–Robinson buffer solution was studied. It was found that 1a is irreversibly reduced in aqueous acidic media on a glassy carbon electrode in one stage with the participation of six electrons and the formation of 5-methyl-6-amino-7-oxo-1,2,4-triazolo[1,5-a]pyrimidin. The electroreduction of 1a in DMF on a background of tetrabutylammonium salts proceeds in two stages, controlled by the kinetics of second-order reactions. In the first stage, the reduction of 1a is accompanied by protonation by the initial compound of the basic intermediate products formed in the electrode reaction (self-protonation mechanism). The second quasi-reversible stage of the electroreduction 1a corresponds to the formation of a dianion radical upon the reduction of the heterocyclic anion 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidin, which is formed upon the potentials of the first peak. The ESR spectrum of the radical dianion was recorded upon electroreduction of Triazid in the presence of Bu4NOH. The effect of the formation of ion pairs on the reversibility of the second peak of the 1a transformation is shown. A change in the rate and regioselectivity of the protonation of the dianion radical in the presence of Na+ and Li+ ions is assumed. The results of studying the electroreduction of 1a by ESR spectroscopy with a TEMPO trap make it possible to assume the simultaneous formation of both a nitroxyl radical and a radical with the spin density localized on the nitrogen at the 4 position of the six-membered ring.

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“…Such reactions between a reduced species and its parent compound are known as self-protonation or father-son reactions and are fairly common in organic compounds with acidic properties. [48][49][50][51][52] The global process, reaction 7, corresponds to the combination of reactions 4 to 6, and implies the transfer of 1.33 e − per H 4 TPP 2+ molecule with the formation of the phlorin cation H 4 TPFH + and of H 2 TPP, agreeing To further confirm the protonation of isophlorin H 4 TPP, cyclic voltammetry was carried out for H 4 TPP 2+ solutions with 0.5 and 1.0 equiv of HClO 4 . Figure 6a shows that the presence of free protons results in the loss of reversibility for Ic/Ia and IIc/IIa, and also induces a new oxidation process IVa.…”

Section: Resultsmentioning

confidence: 99%

Elucidating the Electroreduction Mechanism of the Monoprotonated Octaethylporphyrin. A Comparative Study with the Diprotonated Octaethyl- and meso-Tetraphenyl-porphyrins

Castro-Cruz

Arias-Aranda

Farfán

et al. 2020

J. Electrochem. Soc.

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The electrochemical reduction mechanisms of diprotonated tetraphenylporphyrin (H2TPP) and mono- and diprotonated octaethylporphyrin (H2OEP) were studied in tetrabutylammonium perchlorate/benzonitrile. The diprotonated forms of both porphyrins undergo two one-electron reversible reduction processes forming isophlorin. Contrastingly, monoprotonated H2OEP is reduced in a single process involving a two-electron one-proton transfer that yields two types of short-lived intermediates, isophlorin and neutral phlorin. The existence of intermolecular proton transfer reactions, from the parent protonated porphyrin to the isophlorin or neutral phlorin, to form phlorin cation species (isophlorin protonated at the meso-position) was demonstrated. In-situ UV–vis spectroelectrochemical experiments allowed us to identify the absorption of the isophlorin species of H2TPP but not of H2OEP. These results show that the lack of phenyl substituents increases the rate of protonation at the meso-position. Finally, it was demonstrated that the protonation of the porphyrin macrocycle not only lowers the reduction potentials but also increases the reactivity of the electrogenerated species.

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Evidence of self-protonation on the electrodic reduction mechanism of an anti-Helicobacter pylori metronidazole isotere

Cited by 11 publications

References 17 publications

Preliminary research on 1-(4-bromo-2-nitroimidazol-1-yl)-3-[ 18 F]fluoropropan-2-ol as a novel brain hypoxia PET tracer in a rodent model of stroke

Preliminary research on 1-(4-bromo-2-nitroimidazol-1-yl)-3-[ 18 F]fluoropropan-2-ol as a novel brain hypoxia PET tracer in a rodent model of stroke

Redox Conversions of 5-Methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4triazolo[1,5-a]pyrimidinide L-Arginine Monohydrate as a Promising Antiviral Drug

Elucidating the Electroreduction Mechanism of the Monoprotonated Octaethylporphyrin. A Comparative Study with the Diprotonated Octaethyl- and meso-Tetraphenyl-porphyrins

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