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Frédéric Oddon

Artificial oxygenases: New tools for the asymmetric oxidation catalysis of alkenes and thioethers in the context of the “green chemistry”

Published on 15 December 2010
Thesis presented December 15, 2010

Abstract:
My thesis works have consisted in elaborating new catalysts, in agreement with the “green chemistry” principles, to promote the catalysis of asymmetric oxygenation of thioesters and alkenes. These new catalysts are bio-inorganic hybrids which result from the association of a protein and an iron catalyst.
Our choice for the protein have consisted of the bacterial protein NikA which is able to bind the Fe(EDTA) complex. Then, we have synthesized iron complexes containing N2Py2 ligands (two amine and two pyridine moieties), a favorable environment for metal-based chemistry. On the amino moieties, were added one or two carboxyl groups to allow the recognition with NikA. The catalytic studies of these complexes in alkenes and thioesters​ oxidation have shown that the presence of one carboxyl moiety alter slightly the reactivity of the catalyst, but two carboxyl groups poisoned totally the catalyst. The obtention​ of the structure of one complex and several spectroscopic analyses have shown uncommon features for theses complexes, such as the coordination of carboxyl groups by the carbonyl moiety to the iron center, and the formation of the species Fe(II)Cl42-, as counter-ion, when the complexes are prepared with Fe(II)Cl2.
The NikA/Fe(N2Py2) hybrids were tested in sulfoxidation catalysis showing an enhanced activity without (or very few) sulfone production, opposite to the corresponding complexes alone which afford both sulfoxide and sulfone. Besides, we have determined crystallographic structure of some hybrids and some novel configurations for this type of complexes have been observed. Unfortunately, we have obtained poor enantioselectivities (ee = 11%). To solve this problem, directed mutagenesis experiences, based on crystallographic structure of the hybrids and on docking studies, are envisaged. To conclude, new artificial metalloenzymes have been designed. They will serve as basis for new more optimized systems.

Keywords:
Asymmetric catalysis, epoxidation, sulfoxidation, iron complexes, bio-inorganic hybrids, green chemistry

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