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Descripción
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| Abstract A key step in the metabolic degradation of biphenyl xenobiotics is catechol formation upon dehydrogenation of cis- and trans-dihydrodiols in prokaryotic and eukaryotic pathways, respectively. Structure and thermodynamics of stereoisomers of cis-, trans-2,3-biphenyl-dihydrodiols (I) and their dehydrogenation products (hydroxyketones, II), as well as final catechol (2,3-biphenyldiol, III) are studied by means of ab initio MP2/6-311++G(2df,2p)//MP2/6-311G(d,p) calculations. Formation of stereoisomers I and II is exothermic and endergonic, whereas III is enthalpically and entropically driven. Dehydrogenations are endothermic (¿H ~ 1.5¿4 kcal mol¿1) and exergonic (¿G ~ ¿5 to ¿7.5 kcal mol¿1) without noticeable differences between cis and trans pathways, although the same keto stereoisomer II-(2S) is found to be the more favored product from both cis- and trans-I. The final II ¿ III tautomerization is thermodynamically enhanced (¿H ~ ¿27, ¿G ~ ¿28 kcal mol¿1) but the process is shown to have a large activation energy if it had to occur via unimolecular path. Although this tautomerization is generally assumed to be a nonenzymatic process as it involves rearomatization of an oxygenated ring, proton transfer with an anionic intermediate might be a more probable process. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009 | |
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Internacional
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JCR del ISI
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Si |
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Título de la revista
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JOURNAL OF COMPUTATIONAL CHEMISTRY |
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ISSN
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0192-8651 |
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Factor de impacto JCR
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3,39 |
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DOI
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Número de revista
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0 |
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