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Catalytic Amine Oxidation under Ambient Aerobic Conditions: Mimicry of Monoamine Oxidase B.

Murray AT, Dowley MJ, Pradaux-Caggiano F, Baldansuren A, Fielding AJ, Tuna F, Hendon CH, Walsh A, Lloyd-Jones GC, John MP, Carbery DR - Angew. Chem. Int. Ed. Engl. (2015)

Bottom Line: Reported herein is that the combination of a synthetic flavin and alloxan generates a catalyst system which facilitates biomimetic amine oxidation.Mechanistic and electron paramagnetic (EPR) spectroscopic data supports the conclusion that the reaction proceeds through a radical manifold.This data provides the first example of a biorelevant synthetic model for monoamine oxidase B activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath (UK).

No MeSH data available.


EPR spectra of 2 a′ and 4 a′, and DFT-calculated spin densities measured from solutions of 2 a + Me2S (top) and 2 a + Me2S + 3 a + 1 a (bottom).
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fig01: EPR spectra of 2 a′ and 4 a′, and DFT-calculated spin densities measured from solutions of 2 a + Me2S (top) and 2 a + Me2S + 3 a + 1 a (bottom).

Mentions: Upon attempted in situ 1H NMR analysis, the inability to locate the lock signal suggested paramagnetic behavior. Accordingly, EPR studies at the X-band were initiated. Mixing 2 a and Me2S generated the flavin radical cation 2 a′ (Figure 1). The structure was further confirmed by pulsed EPR studies. In particular, the protonation state of 2 a′ was assessed by electron spin echo envelope modulation (ESEEM), and is a rare example of an aerobically generated flavin semiquinone, having demonstrable relevance to catalysis, observed by EPR spectroscopy.[20] The use of a strong hydrogen-bonding solvent, trifluoroethanol, may aid the stabilization of the semiquinone formation, as discussed by Massey and co-workers, for flavins with amino acids.[21] Upon sequential addition of alloxan and amine, a new EPR spectrum was observed and characterized as the radical 4 a′, and is consistent with charge-transfer-initiated hydrogen-atom abstraction from 4 a. Hybrid-DFT and post-Hartree Fock calculations were performed on 2 a′ and 4 a′ and the spin density isosurfaces are shown in Figure 1.[22] Importantly, the theoretical calculations quantify the local spin density distribution, thus further corroborating the simulations of the continuous-wave EPR spectra.[23]


Catalytic Amine Oxidation under Ambient Aerobic Conditions: Mimicry of Monoamine Oxidase B.

Murray AT, Dowley MJ, Pradaux-Caggiano F, Baldansuren A, Fielding AJ, Tuna F, Hendon CH, Walsh A, Lloyd-Jones GC, John MP, Carbery DR - Angew. Chem. Int. Ed. Engl. (2015)

EPR spectra of 2 a′ and 4 a′, and DFT-calculated spin densities measured from solutions of 2 a + Me2S (top) and 2 a + Me2S + 3 a + 1 a (bottom).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4524416&req=5

fig01: EPR spectra of 2 a′ and 4 a′, and DFT-calculated spin densities measured from solutions of 2 a + Me2S (top) and 2 a + Me2S + 3 a + 1 a (bottom).
Mentions: Upon attempted in situ 1H NMR analysis, the inability to locate the lock signal suggested paramagnetic behavior. Accordingly, EPR studies at the X-band were initiated. Mixing 2 a and Me2S generated the flavin radical cation 2 a′ (Figure 1). The structure was further confirmed by pulsed EPR studies. In particular, the protonation state of 2 a′ was assessed by electron spin echo envelope modulation (ESEEM), and is a rare example of an aerobically generated flavin semiquinone, having demonstrable relevance to catalysis, observed by EPR spectroscopy.[20] The use of a strong hydrogen-bonding solvent, trifluoroethanol, may aid the stabilization of the semiquinone formation, as discussed by Massey and co-workers, for flavins with amino acids.[21] Upon sequential addition of alloxan and amine, a new EPR spectrum was observed and characterized as the radical 4 a′, and is consistent with charge-transfer-initiated hydrogen-atom abstraction from 4 a. Hybrid-DFT and post-Hartree Fock calculations were performed on 2 a′ and 4 a′ and the spin density isosurfaces are shown in Figure 1.[22] Importantly, the theoretical calculations quantify the local spin density distribution, thus further corroborating the simulations of the continuous-wave EPR spectra.[23]

Bottom Line: Reported herein is that the combination of a synthetic flavin and alloxan generates a catalyst system which facilitates biomimetic amine oxidation.Mechanistic and electron paramagnetic (EPR) spectroscopic data supports the conclusion that the reaction proceeds through a radical manifold.This data provides the first example of a biorelevant synthetic model for monoamine oxidase B activity.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Bath, Claverton Down, Bath (UK).

No MeSH data available.