Multiple active intermediates in oxidation reaction catalyzed by synthetic heme-thiolate complex relevant to cytochrome p450.
We have studied oxidation reactions using a synthetic heme-thiolate (SR complex) in order to ascertain the contributions of multiple intermediates derived from heme-thiolate to the oxygen atom transfer reaction to substrate. First, degradation of peroxyphenylacetic acid (PPAA) was examined in the presence of various substrates. The O-O bond cleavage mode of PPAA was clearly dependent on the reactivity of the substrate, and an easily oxidizable substrate enhanced heterolytic O-O bond cleavage. Second, competitive oxidations of cyclooctane and cyclooctene were carried out with various peroxybenzoic acids containing a series of substituents at the para-position as an oxygen source. The ratios of alkane hydroxylation rate/alkene epoxidation rate were dependent on the nature of the para-substituent of the oxidant. We conclude that substrate and oxidant interact with each other during the oxygen atom transfer reaction, that is, oxidation reaction occurs before O-O bond cleavage, even in the reaction catalyzed by heme-thiolate, which is considered to promote O-O bond cleavage. The results of an (18)O-incorporation study that is frequently performed to determine the active intermediates derived from iron porphyrins were consistent with this conclusion.
Suzuki
Noriyuki
N
Contribution from the Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Japan.
Higuchi
Tsunehiko
T
Nagano
Tetsuo
T
D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000378:metabolism*
D013438:Sulfhydryl Compounds; D006418:Heme; D003577:Cytochrome P-450 Enzyme System