On the Mechanism of Cytochrome P450-Catalyzed Oxidations: Reaction of a New Enzyme Model with a Radical Clock

Abstract

trans-2-Phenyl-methylcyclopropane was oxidized using PhIO and a P450 enzyme model carrying a SO₃ ^- ligand coordinating to iron. Analysis of the product distribution revealed a ratio of 9:1 of the non-rearranged cyclopropyl methanol 18 over 1,1-allyl phenyl methanol 16. Given the rate of rearrangement k = 1.8·10¹¹ sec^-1 of the phenyl cyclopropyl methyl radical 14 in solution, the life time of the intermediate radical cluster I _C-H can be calculated as 625 fsec. The hydroxylation proceeds by concerted non-synchronous ‘O’-insertion into the C-H bond of the methyl group.

Key words - catalysis - enzyme models - heme-thiolate proteins - iron porphyrins - radical clock - radical rearrangement

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