Katarzyna Grubel - Regioselective Aliphatic Carbon- Carbon Bond Cleavage by a Model System of Relevance to Iron-Containing Acireductone Dioxygenase

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      Publication Details (including relevant citation   information):

      Allpress, C. J.; Grubel, K.; Szajna-Fuller, E.; Arif, A. M.;   Berreau, L. M. Journal of American Chemical Society  2012, 135, 659-668.

      Abstract:

     
        Abstract Image 
     

        Mononuclear Fe(II) complexes     ([(6-Ph2TPA)Fe(PhC(O)C(R)C(O)Ph)]X     (3-X: R = OH, X = ClO4 or OTf;     4: R = H, X = ClO4)) supported by     the 6-Ph2TPA chelate ligand (6-Ph2TPA =     N,N-bis((6-phenyl-2-pyridyl)methyl)-N-(2-pyridylmethyl)amine)     and containing a β-diketonate     ligand bound via a six-membered chelate ring have been     synthesized. The complexes have all been characterized by     1H NMR, UV–vis, and infrared spectroscopy and     variably by elemental analysis, mass spectrometry, and X-ray     crystallography. Treatment of dry CH3CN solutions of     3-OTf with O2 leads to oxidative     cleavage of the C(1)–C(2) and     C(2)–C(3) bonds of the     acireductone via a     dioxygenase reaction, leading     to formation of carbon    monoxide and 2 equiv of benzoic acid as well as two other     products not derived from dioxygenase reactivity:     2-oxo-2-phenylethylbenzoate and benzil. Treatment of     CH3CN/H2O solutions of     3-X with O2 leads to the formation     of an additional product, benzoylformic acid, indicative of the     operation of a new reaction pathway in which only the C(1)–C(2)     bond is cleaved. Mechanistic studies show that the     change in regioselectivity is due to the hydration of a vicinal     triketone intermediate in the presence of both an iron center and water. This is the first     structural and functional model of relevance to iron-containing acireductone dioxygenase    (Fe-ARD′), an enzyme in the methionine salvage pathway that     catalyzes the regiospecific oxidation of     1,2-dihydroxy-3-oxo-(S)-methylthiopentene to form     2-oxo-4-methylthiobutyrate. Importantly, this model system is found to control the     regioselectivity of aliphatic     carbon–carbon bond cleavage by changes involving an     intermediate in the reaction pathway, rather than by the     binding mode of the substrate, as had been proposed in studies     of acireductone enzymes.  

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/ja3038189