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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 (k_H/k_D = 9−11 at 10 °C) were shown not to be complicated by tunneling effects by variable temperature studies with two …