Theoretical Investigation of C-H Hydroxylation by (N4Py)Fe~(IV)=O~(2-):An Oxidant More Powerful than P450?

摘要

High-valent iron-oxo intermediates are invoked in the catalytic cycles of mononuclear iron enzymes that carry out essential oxidative transformations.Such species have been characterized for heme enzymes such as peroxidases and for nonheme enzymes such as TauD.In cytochrome P450,this species was implicated but still awaits full characterization.In heme enzymes,the iron- oxo active species,so-called compound I (Cpd I),is typified by an Fe~(IV)O unit coordinated to a porphyrin in its radical cation state,hence (Por~(centre dot+))Fe~(IV)O.Cpd I is a potent oxidant able to oxidize nonactivated bonds;for example,P450 Cpd I hydroxylates inert C-H bonds with bond dissociation energies exceeding 95 kcal/mol.A second intermediate,the corresponding one-electron reduced species,termed Cpd II,involves (Por)Fe~(IV)O [or (Por_Fe~(IV)OH] and is a sluggish reagent for C-H bond activation compared with Cpd I.However,many nonheme iron enzymes are proposed to utilize Fe~(IV)O intermediates,analogous to Cpd II,to effect substrate oxidations and even perform C-H hydroxylation (e.g.,TauD).