Reactivity of 1,4-dihydropyridines toward alkyl, alkylperoxyl radicals, and ABTS radical cation.
A series of C4-substituted 1,4-dihydropyridines (DHP) with either secondary or tertiary nitrogen in the dihydropyridine ring were synthesized. All of these compounds together with some commercial DHP derivatives were tested for potential scavenger effects toward alkyl, alkylperoxyl radicals, and ABTS radical cation in aqueous media at pH 7.4. Kinetic rate constants were assessed either by UV/vis spectroscopy or GC/MS techniques. Tested compounds reacted faster toward alkylperoxyl radicals and ABTS radical cation than alkyl ones. N-Ethyl-substituted DHPs showed the lowest reactivity. Kinetic results were compared with either trolox or nisoldipine. Using deuterium kinetic isotope effect studies, we have proved that the hydrogen of the 1-position of the DHP ring is involved in the proposed mechanism. This fact is mostly noticeable in the case of alkyl radicals. In all cases, the respective pyridine derivative was detected as the main product of the reaction.
López-Alarcón
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Laboratory of Biolectrochemistry, Laboratory of Organic Synthesis and Molecular Modeling, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, P.O. Box 233, Santiago, Chile.
Navarrete
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Camargo
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Squella
J A
JA
Núñez-Vergara
L J
LJ
D052160:Benzothiazoles; D002412:Cations / Q000737:chemistry; D002839:Chromans / Q000737:chemistry; D004095:Dihydropyridines / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015737:Nisoldipine / Q000737:chemistry; D010545:Peroxides / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013451:Sulfonic Acids / Q000737:chemistry*; D014810:Vitamin E / Q000031:analogs & derivatives
D052160:Benzothiazoles; D002412:Cations; D002839:Chromans; D004095:Dihydropyridines; D016166:Free Radical Scavengers; D005609:Free Radicals; D010545:Peroxides; D013451:Sulfonic Acids; D014810:Vitamin E; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D015737:Nisoldipine; C038806:1,4-dihydropyridine; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid