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Extradiol oxidative cleavage of catechols by ferrous and ferric complexes of 1,4,7-triazacyclononane: Insight into the mechanism of the extradiol catechol dioxygenases
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UNSPECIFIED (2001) Extradiol oxidative cleavage of catechols by ferrous and ferric complexes of 1,4,7-triazacyclononane: Insight into the mechanism of the extradiol catechol dioxygenases. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 123 (21). pp. 5030-5039. ISSN 0002-7863.
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Abstract
The major oxygenation product of catechol by dioxygen in the presence of FeCl2 or FeCl3, 1,4,7-triazacyclononane (TACN), and pyridine in methanol is the extradiol cleavage product 2-hydroxymuconic semi-aldehyde methyl ester (Lin, G.; Reid, G.; Bugg, T. D. I-I. J. Chem. Sec. Chem. Commun. 2000, 1119-1120). Under these conditions, extradiol cleavage of a range of 3- and 4-substituted catechols with electron-donating substituents is observed. The reaction shows a preference in selectivity and rate for iron(II) rather than iron(III) for the extradiol cleavage, which parallels the selectivity of the extradiol dioxygenase family. The reaction also shows a high selectivity for the macrocyclic ligand, TACN, over a range of other nitrogen-and oxygen-containing macrocycles. Reaction of anaerobically prepared iron-TACN complexes with dioxygen gave the same product as monitored by UV/vis spectroscopy. KO2 is able to oxidize catechols with both electron-donating and electron-withdrawing substituents, implying a different mechanism for extradiol. cleavage. Saturation kinetics were observed for catechols, which fit the Michaelis-Menten equation to give k(cat)(app) = 4.8 x 10(-3) s(-1) for 3-(2 ' ,3 ' -dihydroxyphenyl)propionic acid. The reaction was also found to proceed using monosodium catecholate in the absence of pyridine, but with different product ratios, giving insight into the acid/base chemistry of extradiol cleavage. In particular, extradiol cleavage in the presence of iron(II) shows a requirement for a proton donor, implying a role for an acidic group in the extradiol dioxygenase active site.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Journal or Publication Title: | JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | ||||
Publisher: | AMER CHEMICAL SOC | ||||
ISSN: | 0002-7863 | ||||
Official Date: | 30 May 2001 | ||||
Dates: |
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Volume: | 123 | ||||
Number: | 21 | ||||
Number of Pages: | 10 | ||||
Page Range: | pp. 5030-5039 | ||||
Publication Status: | Published |
Data sourced from Thomson Reuters' Web of Knowledge
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