Mediator oxygen

Scheme 9.12 Soybean lipoxygenase (SBLO)-mediated oxygenation of fatty acid derivatives.

Ingelman-Sundberg, M. and Ekstrom, G. (1982). Aniline is hydroxylated by the cytochrome P-450-dependent hydroxyl radical-mediated oxygenation mechanism. Biochem. Biophys. Res. Commun. 106, 625-631. 

Paytan A, Luz B, Kolodny Y, Neori A (2002) Biologically mediated oxygen isotope exchange between water and phosphorus. Global Biogeochem Cycles 16-13 1-7 Paytan A, Kastner M, Campbell D, Thiemens M (2004) Seawater sulfur isotope fluctuations in the Cretaceous, Science 304 1663-1665... 

To round off the overview of Cu-mediated oxygenation and oxidation reactions and to give a glance at the broader usefulness of Cu, a few examples of... 

Subsequent hydride shift-mediated oxygen transposition should then generate 370. The furanophane 367 in turn, featuring a trisubstituted double bond with ( )-configuration (necessary for the success of the TADA reaction), was to be generated by RCM. 

A closely related reaction is seen in the copper-mediated oxygenation of bis(2-ben-zimidazolyl)methanes to bis(2-benzimidazolyl)ketones (Fig. 9-31). This is a general reaction shown by many bis(heteroaryl)methanes. The reaction of the iron(n) complex... 

Prior to the onset of sulfate reduction extensive organic matter degradation can occur by bacterially-mediated oxygen reduction (see Chapter 4). The influence of benthic bacterial activity under aerobic conditions on carbonate mineral dissolution has been nicely demonstrated by Moulin et al. (1985) for pore waters from sediments of the Gulf of Calvi, Corsica. Under aerobic conditions, the oxidation of organic matter may be written ... 

Heterolytic oxygen transfer processes can be divided into two categories based on the nature of the active oxidant an oxometal or a peroxometal species (Fig. 4.10). Catalysis by early transition metals (Mo, W, Re, V, Ti, Zr) generally involves high-valent peroxometal complexes whereas later transition metals (Ru, Os), particularly first row elements (Cr, Mn, Fe) mediate oxygen transfer via oxometal species. Some elements, e.g. vanadium, can operate via either mechanism, depending on the substrate. Although the pathways outlined in Fig. 4.10... 

Schultz, B. E., Gheller, S. F., Muetterties, M. C., Scott, M. J., and Helm, R. H., 1993, Molybdenum-mediated oxygen atom h ansfer an improved analogue reaction system of the molybdenum oxotransferases, J. Am. Chem. Soc. 115 2714fi2722. 

Iron-mediated oxygen transfer is also at play in the chloroperoxidase (CPO) catalyzed epoxidation of simple alkenes, which has the added advantage of providing high enantiomeric excesses. For example, c/s-2-heptene 35 is converted to the chiral epoxide 36 in 78% yield. However, the protocol is generally limited to fairly accessible disubstituted alkenes the more imbedded olefin of cis-3-heptene only undergoes 12% conversion, while the epoxides derived from terminal olefins tend to alkylate the enzyme and serve as suicide inhibitors <0374701>. 

Rizzo, W. M., and Christian, R. R. (1996). Significance of subtidal sediments to heterotrophically-mediated oxygen and nutrient dynamics in a temperate estuary. Estuaries 24, 475—487. 

Paytan A., Kolodny Y., Neori A., and Luz B. (2002) Rapid biologically mediated oxygen isotope exchange between water and phosphate. Global Biogeochem. Cycles 16, 10.1029/2001GB001430. 

Honda, E, Gin, D Y, C-2 Hydroxyglycosylation with glycal donors. Probing the mechanism of sulfonium-mediated oxygen transfer to glycal enol ethers, J. Am. Chem. Soc., 124, 7343-7352, 2002. 

In addition to the design of the solubility properties, the reactivity of organome-tallic species toward CO2 [13] (and many other potential supercritical reaction media) must be considered as important criteria for the choice of the catalyst. For example, the bisallyl ruthenium complex shown in Table 1 cannot be utilized as a precursor for ring-opening metathesis polymerization (ROMP) in SCCO2, because the insertion of CO2 into the Ru-allyl bond prevents the initiation mechanism [14]. Metal-mediated oxygen transfer to form CO and phosphine oxide was found to lead to deactivation of the [Ni(cod)2]/PMe3 (cod = 1,5-m-cycloocta-diene) catalyst system [15]. On the other hand, the reactivity of CO2 with metal... 

B. Meunier, Potassium monopersulfate-Just another primary oxidant or a highly versatile oxygen atom donor in metalloporphyrin-mediated oxygenation and oxidation reactions. New J. Chem. 16 (1992) 203. 

Schmidt M, Giessl A, Laufs T, Hankeln T, Wolfrum U, et al. 2003. How does the eye breathe Evidence for neuroglobin-mediated oxygen supply in the mammalian retina. J Biol Chem 278 1932-1935. 

The holy grail of oxidation chemistry is the design of catalytic systems capable of mediating oxygen transfer from dioxygen, without the need for a sacrificial reductant, i.e. a Mars-van Krevelen mechanism [18] in the liquid phase. Indeed, the confinement of substrate molecules in the micropores of molecular sieves might be expected to create quasi gas phase conditions conductive to such a mechanism at the expense of free radical chain autoxidation (we note, however, that a mechanism involving two metal centres as shown in eq. 12 would be difficult to achieve in a molecular sieve). 

Within the context of dioxirane-mediated oxygen transfer, the orientation of the dioxirane with respect to the substrate olefin has important implications for potential stereoinduction models. Spiro (A) and planar (B) transition states rep-... 

Brix, H., 1993. Macrophyte-mediated oxygen transfer in wetlands Transport mechanisms and rates. In Moshiri, G.A. (Ed.), Constructed Wetland for Water Quality Improvement,... 

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