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Hydroxylation, Epoxidation, and DNA Cleavage Reactions Mediated by the Biomimetic Mn-TMPyP/O2/Sulfite Oxidation System† Karine Wietzerbin,‡ James G. Muller,*,§ Rachel A. Jameton,§ Genevie` ve Pratviel,‡ Jean Bernadou,*,‡ Bernard Meunier,*,‡ and Cynthia J. Burrows*,§ Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse Cedex 4, France, and Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850 ReceiVed May 17, 1999
Autoxidation of sulfite is catalyzed by the water-soluble complex (meso-tetrakis(4-N-methylpyridiniumyl)porphyrinato)manganese(III) (Mn-TMPyP), leading to an intermediate species capable of hydroxylation of p-isopropylbenzoic acid, epoxidation of carbamazepine, and generation of single-strand breaks both in plasmid ΦX174 DNA and in a 167-base-pair fragment of pBR322. 18O-Labeling studies confirm that the high-valent manganese-oxo intermediate undergoes oxo-hydroxo tautomerism in competition with oxidation of substrate or reduction by excess sulfite. In contrast to the classical reductive activation of dioxygen by metalloporphyrins (dithiothreitol or ascorbate in the presence of O2), a mechanism is proposed in which SO3•-, formed by oxidation with MnIII, is trapped by O2, leading to a species (SO5•-) capable of generating a MnVdO complex. Importantly, these studies point to the use of an alternative, biocompatible oxidation system compared to the preformed oxidant KHSO5.
Introduction The development of procedures for the hydroxylation of alkanes or the epoxidation of olefins with molecular oxygen is an important industrial and synthetic goal.1 Since the pioneering work of Tabushi,2,3 biomimetic oxygen atom transfers based on metalloporphyrin catalysts have been developed using either oxygen atom donors or molecular oxygen and a reducing agent.4,5 In biology, O2 is the oxidant in combination with NAD(P)H as reducing agent, although several biomimetic examples of ascorbate or thiols as the reductant have also been reported.6 In contrast, the use of sulfite, SO32- (and HSO3- in neutral, aqueous solution), as the reductant for O2 has hardly been investigated for applications in catalytic oxidation.7 Mechanistic studies of sulfite autoxidation have demonstrated the important role that transition metals such as manganese may play in the one-electron processes associated with the reaction, but the majority of these systems lead to formation of sulfoxyl radicals as the key products of sulfite autoxidation.8-14 In contrast, recent † Dedicated to Professor John A. Osborn on the occasion of his 60th birthday. ‡ Laboratoire de Chimie de Coordination du CNRS. § University of Utah. (1) Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis. The Applications and Chemistry of Catalysis by Soluble Transition Metal Complexes, 2nd ed.; Wiley: New York, 1992. (2) Tabushi, I.; Koga, N. J. Am. Chem. Soc. 1979, 101, 6456-6458. (3) Tabushi, I.; Kodera, M.; Yokoyama, M. J. Am. Chem. Soc. 1985, 107, 4466-4473. (4) Groves, J. T.; Han, Y.-Z. In Cytochrome P-450: Structure, Mechanism and Biochemistry, 2nd ed.; Ortiz de Montellano, P. R., Ed.; Plenum: New York, 1995; pp 3-48. (5) Meunier, B. Chem. ReV. 1992, 92, 1411-1456. (6) Ortiz de Montellano, P. R. Cytochrome P-450: Structure, Mechanism and Biochemistry, 2nd ed.; Plenum: New York, 1995. (7) Song, Y.; Yang, C.-H.; Kluger, R. J. Am. Chem. Soc. 1993, 115, 43654366. (8) Brandt, C.; van Eldik, R. Chem. ReV. 1995, 95, 119-190. (9) Connick, R. E.; Zhang, Y.-X. Inorg. Chem. 1996, 35, 4613-4621.
studies of methemoglobin and manganese porphyrins suggest that these catalysts may provide access to high-valent metaloxo species.7,15,16 Here we report the possibility of promoting hydroxylation and epoxidation reactions involving manganese(V)-oxo porphyrin species, reminiscent of the reactive intermediate described for cytochrome P-450, via sulfite autoxidation catalyzed by MnTMPyP.17-19 In addition, the potential application of this system in biological oxidation is also illustrated by results on oxidative DNA cleavage.20 Importantly, these studies point to the use of an alternatiVe, biocompatible oxidation system compared to the preformed oxidant KHSO5. To determine whether the oxygenation reaction occurs via a metal-oxo intermediate or via free radicals (see refs 21 and 22 for reviews on this controversial debate), we used the oxo-hydroxo tautomerism mechanism23,24 (previously named “redox tautomerism”) as an easy method to (10) Coichev, N.; van Eldik, R. Inorg. Chim. Acta 1991, 185, 69-73. (11) Berglund, J.; Fronaeus, S.; Elding, L. I. Inorg. Chem. 1993, 32, 45274538. (12) Lim, P. K.; Hamrick, G. T. J. Phys. Chem. 1984, 88, 1133-1136. (13) Mukhopadhyay, S.; Banerjee, R. J. Chem. Soc., Dalton Trans. 1993, 933-939. (14) Bobba, V. M.; Giraudi, G.; Menasti, E. Transition Met. Chem. 1988, 13, 256-260. (15) Chen, S.-M. J. Mol. Catal. A: Chem. 1996, 112, 277-285. (16) Chen, S.-M. J. Electroanal. Chem. Interfacial Electrochem. 1996, 407, 123-130. (17) Mn-TMPyP stands for the pentaacetate of the diaquamanganese(III) derivative of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin. See the following references for details on this efficient DNA cleaver. (18) Bernadou, J.; Pratviel, G.; Bennis, F.; Girardet, M.; Meunier, B. Biochemistry 1989, 28, 7268-7275. (19) Pitie´, M.; Pratviel, G.; Bernadou, J.; Meunier, B. Proc. Natl. Acad. Sci. U.S.A. 1992, 89, 3967-3971. (20) Muller, J. G.; Hickerson, R. P.; Perez, R. J.; Burrows, C. J. J. Am. Chem. Soc. 1997, 119, 1501-1506. (21) Ingold, K. U.; MacFaul, P. A. In Biomimetic Oxidation Catalyzed by Transition Metals; Meunier, B., Ed.; Imperial College Press: London, 1998; Chapter 2.
10.1021/ic990537h CCC: $18.00 © 1999 American Chemical Society Published on Web 08/13/1999
4124 Inorganic Chemistry, Vol. 38, No. 18, 1999
Wietzerbin et al.
Scheme 1. Mechanisms To Account for the Labeling Observed in Hydroxylation and Epoxidation Reactions in Experiments Using H218O (b ) 18O)
Table 1. Products Obtained in the Oxidation of 4-Isopropylbenzoic Acid (BA) and Carbamazepine (CBZ) Catalyzed by Mn-TMPyP in the Presence of KHSO5 or Na2SO3/O2 consub- mode of concn, version, % stratea activation mM BA
KHSO5 Na2SO3
CBZ
KHSO5 Na2SO3
1 10 1 10 2c 10d
48 93 34.5 60 90
