Model complexes as probes of heme and nonheme enzymatic mechanisms: (1) Ferric peroxo porphyrin complexes as mimics of P450 enzymes using the ferric peroxo species as an active oxidant. (2) Strongly oxidizing iron (III) complexes as models of the active s

Ferric peroxo porphyrin complexes were synthesized and investigated for their ability to mimic the reactivity of P450 enzymes thought to possibly use a ferric peroxo porphyrin species as an active intermediate. The nucleophilic ferric peroxo porphyrin complex, [Fe(TMP)O2]-, was reacted with the natural substrate of the enzyme aromatase and was found to give epoxidation of the enone moiety rather than the enzymatic product, the deformylated and aromatized substrate. The synthesis of a substrate that mimicked the enolized state of the natural substrate when in the active site resulted in a substrate-like molecule that reacted cleanly with [Fe(TMP)O 2]- to give the expected aromatized product. This result supports the idea that aromatase does indeed use a ferric peroxo porphyrin species as the active oxidant.;The mechanism of the reaction of [Fe(TMP)O2]- with aldehydes was investigated. The mechanism of deformylation with benzylic aldehdyes is likely different from deformylation with aromatase substrate-like aldehydes as in the former case we observe a stable intermediate after the disappearance of the [Fe(TMEP)O2]- species while in the latter case direct conversion to Fe(TMP)OH is observed. The aldehyde reactivity profile of [Fe(TMP)O2]- indicates that in the case of benzylic aldehydes the stability of a product radical directly correlates with the observed yields. NMR evidence suggests that the stable intermediate observed in the reaction of [Fe(TMP)O2] - with benzylic aldehydes is a ferrous porphyrin species.;Preliminary reactivity studies of 3-hydroxy-3-methyl-2-butanone with [Fe(TMP)O2]- indicate that a reaction occurs to give acetate and a porphyrin precipitate. A similar reaction occurs when 17alpha-demethylase reacts with an alpha-hydroxyketone steroid compound. Therefore, this result supports the hypothesis that a ferric peroxo porphyrin species is the active oxidant used in the third catalytic step of the enzyme 17alpha-demethylase.;The nonheme enzyme lipoxygenase oxidizes the bis-allylic methylene carbon of fatty acids to give fatty acid hydroperoxides. The strongly oxidizing complex Fe(OTf)3 is able to oxidize the bis-allylic methylene carbon of 1-methyl-1,4-cyclohexadiene. The carbon-hydrogen bond activation achieved by this model complex is similar to the bond activation observed in the catalytic reaction of lipoxygenase. The fact that Fe(OTf)3 reacts with 1-methyl-1,4-cyclohexadiene to give toluene under anaerobic conditions suggests that the active site iron species of lipoxygenase may be strongly oxidizing enough to react with its substrate without the need for oxygen activation.;Strongly electron withdrawing peracids are able to react with inactivated alkanes to give alcohols via a nonradical mechanism. The attempt to catalyze the hydroxylation of alkanes with iron complexes in the presence of electron deficient alkanes is reported. Reaction times decrease from 20 hours to 2 hours upon the addition of metal complexes to a solution containing alkane and peracid, however, the mechanistic pathway switches from nonradical to radical. The addition of spin traps to prohibit radical reactivity did not alter the course of the metal catalyzed reactions. (Abstract shortened by UMI.).