Catalysts P450 monooxygenase

The most attractive aspect of cytochrome P450 monooxygenases is that they are able to perform chiral recognitions and enantioselective oxygenations which are induced by the protein around the active site. This aspect can be mimicked using synthetic chiral catalysts. 

Synthesis of octanol regiosio-mers via asymmetric hydroxylation of n-octane with a wild-type whole-cell catalyst containing a P450-monooxygenase. 

Electrocatalytic N2O reduction mediated by heme proteins such as Mb or cytochrome P450 monooxygenase has been demonstrated in film-modified electrodes [145, 212]. The authors suggest two-electron redox processes occur with the catalyst shuttling between the Ee(I) and Fe(III) states, e.g. as shown in Scheme 2.14. 

Figure 8. Hydroxylation of L-limoneneto (-)-perillyl alcohol by cytochrome P450. Growing cells of P. putida GPol2 (pG Ec47AB) (pCom8-PFRl 500) containing the P450 alkane monooxygenase of Mycobacterium sp. strain HXN-1500 are used as catalyst.

Metallo-phthallocyanine (MePc) complexes are known as mild oxygenation catalysts for alkanes and alkenes and as functional models for enzymes, more in particular for monooxygenases like Cytochrome P450.[44] Among the many possible supports for such complexes, zeolite FAU topologies1451 are excellent materials for their encapsulation. [46 50] The low solubility of Me Pc complexes in general and their tendency to form adducts even in solution, giving rise to self-oxidation and subsequent self-destruction phenomena, make them the ideal candidates for their distribution as individual species on a solid support. 

The P450 scaffold has evolved to serve as a ubiquitous monooxygenase. Nature manipulated this structure to create an immense library of P450s with finely-tuned activities and specificities. The CPO scaffold has not become a ubiquitous oxidation catalyst, but it supports high peroxygenase activity and may be superior to P450s for chemical transformations of certain substrates, particularly when it has been evolved in the laboratory for optimal performance in these applications. 

Studies of the epoxidation of styrene and sulfoxidation of thioanisoles by cytochrome P450, a monooxygenase of known structure, show that the absolute stereochemistry of the reaction can be predicted by molecular dynamics calculations. Extension of this approach to other reactions, and to more complicated substrates, should provide an important step towards the rationalization of oxidative metabolism and the construction of tailor made oxidative catalysts. 

Many chemical model systems based on metalloporphyrin catalysts and mimicking cytochrome P450-dependent monooxygenases have been described during these last decade. Several review articles have been devoted to these systems 2-10. in that context, very recent results about the preparation and catalytic properties of new homogeneous and supported catalysts will be described in a first chapter. In the second chapter, some preliminary results showing that the oxidation of alkanes by a dioxygenase-like mechanism could occur in the presence of iron porphyrin catalysts activated either photochemically or thermally, will be reported. 

Two kinds of systems based on Fe(III) or Mn(III) porphyrins are available now for the oxidation of hydrocarbons. The first ones involve such a metalloporphyrin catalyst and an oxygen atom donor like PhIO, H2O2 or O2 and a reducing agent 2-10 They reproduce quite well the reactions catalyzed by cytochrome P450-dependent monooxygenases and involve a high-valent metal-oxo active species which is able to epoxidize alkenes, hydroxylate alkanes and aromatic compounds and perform N- or S- oxidations. 

The heme-containing cytochrome P450 catalysts that hydroxylate CH bonds and are active as epoxidation catalysts are known to be monooxygenases. They utilize molecular oxygen as a source of two electrons to catalyze oxygen insertion into a CH bond. The overall electrocatalytic cycle for the oxidation reaction is shown in Scheme... 

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