Kinetics and mechanism of the Cu(I) and Cu(II) flavonolate-catalyzed oxygenation of flavonol. Functional quercetin 2,3-dioxygenase models

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Abstract

The oxygenation of flavonol (flaH) using Cu(II)(fla)2 and Cu(I)(fla)(PPh3)2 catalysts results in oxidative cleavage of the heterocyclic ring to give O-benzoylsalicylic acid (O-bsH) and CO as primary products. The oxygenolysis of flavonol catalyzed by Cu(II)(fla)2 in DMF was followed by electronic spectroscopy and the rate law was found to be - d[flaH]/dt = k(obs)[flaH][Cu(II)(fla)2][O2]. The rate constant, activation energy, activation enthalpy and entropy at 393 K are as follows: k(obs)/s-1 mol-2 dm-6 = (2.02 ± 0.07) x 103, E(a)/kJ mol-1 = 142 ± 6, ΔH(+)/kJ mol-1 = 139 ± 5, and ΔS(+)/J mol-1 K-1 = 168 ± 13. The results of the kinetic measurements of the Cu(I)(fla)(PPh3)2-catalyzed oxygenation shows that in the presence of a large excess of the substrate, the Cu(I)(fla)(PPh3)2 reacts with flavonol in an irreversible step to Cu(II)(fla)2, and, then, the mechanism of the oxygenation is the same as that with the Cu(II)(fla)2-catalyzed reaction. (C) 2000 Elsevier Science B.V.

Original languageEnglish
Pages (from-to)215-224
Number of pages10
JournalJournal of Molecular Catalysis A: Chemical
Volume159
Issue number2
DOIs
Publication statusPublished - Oct 2 2000

Keywords

  • Copper
  • Dioxygenation
  • Flavonolate complexes
  • Quercetinase

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology
  • Physical and Theoretical Chemistry

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