Base (O.-2, e-, or OH-)-induced autoxygenation of organic substrates: a model chemical system for cytochrome P-450-catalyzed monoxygenation and dehydrogenation by dioxygen.

Abstract

When catalytic quantities of superoxide ion (0°-; or of electrons from electrolysis or of OH-) are introduced into a dry acetonitrile solution that contains excess substrate (RH), ambient air (02), 1,2-diphenylhydrazine (PhNHNHPh), and iron(II), the substrate is rapidly and efficiently monoxygenated (e.g., triphenylphosphine --triphenylphosphine oxide, benzyl alcohol --benzaldehyde, diphenylsulfoxide > diphenylsulfone) or dehydrogenated (1,4-cyclohexadiene > benzene Additional insight into the redox chemistry for the elements of the model system is provided by the cyclic voltammograms in Fig. 1. Thus, that the combination of 02 and PhNHNHPh does not react is confirmed by observation of the electrochemistry for each component (Fig. la). However, addition of a catalytic amount (0.1 mM) of 0°-causes a rapid oxidation of PhNHNHPh to azobenzene (PhN=NPh; Fig. lb). Analysis of the product solution confirms that this is a 1:1 stoichiometric process that gives one H202 per PhNHNHPh. When iron(II) and Ph2S(O) are combined with 02 and PhNHNHPh there is no net reaction (Fig. lc). The hydrazine is oxidized irreversibly at +0.6 V vs. SCE (saturated calomel electrode) and the iron(II) exhibits an oxidation peak at +1.8 V vs. SCE. Upon addition of a catalytic quantity of 0°-to this solution, there is a rapid autoxidation of the donor (PhNHNHPh) and substrate [Ph2S(0)] to give PhN=NPh and diphenylsulfone [Ph2S(0)2]; the voltammogram (Fig. ld) indicates that all of the PhNHNHPh is oxidized. Spectrophotometric, gas chromatographic, and titrametric analyses confirm that the process yields -0.3 mol of Ph2S(0)2/mol of donor (PhNHNHPh) in the presence of exAbbreviations: RH, substrate in monoxygenation; DH2, two-electron reductant. 8025The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Models and mechanisms of O‐O bond activation by cytochrome P450

“…Electrochemical investigations support this concept, revealing autoxidation of diphenylhydrazine, when exposed to O 2 , to liberate hydrogen peroxide, which collapses with iron(II) to give an Fe(II)-H 2 O 2 complex directly leading to metabolic turnover [261].…”

“…Substrate transformation posits the participation of structurally similar hydroperoxo‐iron catalysts with different formal oxidation states [258,260], the process being driven to exothermicity via water formation (. Electrochemical investigations support this concept, revealing autoxidation of diphenylhydrazine, when exposed to O 2 , to liberate hydrogen peroxide, which collapses with iron(II) to give an Fe(II)‐H 2 O 2 complex directly leading to metabolic turnover [261].…”

Adventures inRhodococcus — from steroids to explosivesThis article is based on a presentation by Dr. Lindsay Eltis at the 60th Annual Meeting of the Canadian Society of Microbiologists in Hamilton, Ontario, 14 June 2010. Dr. Eltis was the recipient of the 2010 Norgen Biotek Corporation / CSM Award, an annual award sponsored by Norgen Biotek and the Canadian Society of Microbiologists intended to recognize outstanding scientific work in microbiology by a Canadian researcher.

“…4B) shares up to 75% amino acid sequence identity with the cobalt transporters associated with all Co-NHases such as that of R. rhodochrous J1 (Kobayashi and Shimizu 1998). Secondly, the electronic absorption spectrum of ANHase is typical of Co-NHases (Sawyer et al 1984;Mathew et al 1988;Kohyama et al 2006), with an absorption maximum at 414 nm and a shoulder at~350 nm, likely due to S?Co 3+ charge transfer bands. Finally, the production of active ANHase required cobalt but neither copper nor zinc in the growth media (S. Okamoto and L.D.…”

Reactions of theophylline, theobromine and caffeine with Fenton's reagent-simulation of hepatic metabolism

“…A carbinolamine intermediate has been suggested to be the penultimate step in the mechanism of N-dealkylation (Burka et al 1985). A metal-bound peroxide, for example, ferry1 or perferryl intermediates species, has been postulated to be involved in both the catalytic cycle of cytochrome P-450 (Peterson et al 1973) and the Fentontype reaction (Fe"/H,O,), associated primarily with oxygen transfer to the substrate (Sawyer et al 1984).…”