201164-25-2Relevant academic research and scientific papers
Hydroxylation by the Hydroperoxy-Iron Species in Cytochrome P450 Enzymes
Chandrasena, R. Esala P.,Vatsis, Kostas P.,Coon, Minor J.,Hollenberg, Paul F.,Newcomb, Martin
, p. 115 - 126 (2004)
Intramolecular and intermolecular kinetic isotope effects (KIEs) were determined for hydroxylation of the enantiomers of trans-2-(p-trifluoromethylphenyl)cyclopropylmethane (1) by hepatic cytochrome P450 enzymes, P450s 2B1, Δ2B4, Δ2B4 T302A, Δ2E1, and Δ2E1 T303A. Two products from oxidation of the methyl group were obtained, unrearranged trans-2-(p-trifluoromethylphenyl)cyclopropylmethanol (2) and rearranged 1-(p-trifluoromethylphenyl)but-3-en-1-ol (3). In intramolecular KIE studies with dideuteriomethyl substrates (1-d2) and in intermolecular KIE studies with mixtures of undeuterated (1-d0) and trideuteriomethyl (1-d3) substrates, the apparent KIE for product 2 was consistently larger than the apparent KIE for product 3 by a factor of ca. 1.2. Large intramolecular KIEs found with 1-d2 (kH/k D = 9-11 at 10 °C) were shown not to be complicated by tunneling effects by variable temperature studies with two P450 enzymes. The results require two independent isotope-sensitive processes in the overall hydroxylation reactions that are either competitive or sequential. Intermolecular KIEs were partially masked in all cases and largely masked for some P450s. The intra- and intermolecular KIE results were combined to determine the relative rate constants for the unmasking and hydroxylation reactions, and a qualitative correlation was found for the unmasking reaction and release of hydrogen peroxide from four of the P450 enzymes in the absence of substrate. The results are consistent with the two-oxidants model for P450 (Vaz, A. D. N.; McGinnity, D. F.; Coon, M. J. Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 3555), which postulates that a hydroperoxy-iron species (or a protonated analogue of this species) is a viable electrophilic oxidant in addition to the consensus oxidant, iron-oxo.
Catalytic enantioselective cyclopropanation of allylic alcohols using recyclable fluorous disulfonamide ligand
Miura, Tsuyoshi,Itoh, Keisuke,Yasaku, Yumi,Koyata, Naka,Murakami, Yasuoki,Imai, Nobuyuki
, p. 5813 - 5815 (2008/12/22)
Cyclopropanation of allylic alcohols with Et2Zn and CH2I2 in the presence of a catalytic amount of fluorous disulfonamide 3 afforded the corresponding cyclopropylmethanols in 69-96% yield with 49-83% ee. The fluorous ligand 3 was readily recovered from the reaction mixture by the fluorous solid-phase extraction (FSPE) and could be reused without a significant loss of the catalytic activity and enantioselectivity.
A Substituted Hypersensitive Radical Probe for Enzyme-Catalyzed Hydroxylations: Synthesis of Racemic and Enantiomerically Enriched Forms and Application in a Cytochrome P450-Catalyzed Oxidation
Toy, Patrick H.,Dhanabalasingam, Bhavani,Newcomb, Martin,Hanna, Imad H.,Hollenberg, Paul F.
, p. 9114 - 9122 (2007/10/03)
The syntheses of racemic and enantiomerically enriched trans-1-methyl-2-(4-(trifluoromethyl)phenyl)cyclopropane (3) and the possible oxidation products from enzyme-catalyzed hydroxylation of 3 at the methyl group are reported. The important intermediate in the production of 3 was the Weinreb amide of the 2-arylcyclopropanecarboxylic acid which could be prepared in diastereomerically pure form and which also served as an intermediate for production of the cyclic oxidation products of 3. Hydroxylation of 3 by the cytochrome P450 isozyme CYP2B1 gave cyclic and ring-opened products. The product ratios support an insertion mechanism for the enzyme-catalyzed hydroxylation reaction in which minor amounts of rearranged products are produced by radical fragmentation within the transition structure of the insertion and by a competing reaction involving a cationic species. Formation of cationic rearrangement products by a heterolytic fragmentation reaction of a first-formed protonated alcohol product is suggested on the basis of the apparent amounts of cationic products formed in the hydroxylation of 3. This pathway for cation production appears to require that the activated enzyme complex (equivalent to enzyme-substrate-H2O2) oxidizes substrate before water dissociates to give an iron-oxo species.
