- Production mechanism of active species on the oxidative bromination following perhydrolase activity
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Hypobromous acid and molecular bromine have been described as the active species involved in the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH). However, the brominating activity of them in a chemical model system was lower than that of the active species produced by the spontaneous reaction between AcOOH and Br-. Consequently, acetyl hypobromite (AcOBr) was suggested as new active species on the bromination by detection of the decarboxylation in the reaction between AcOOH and Br- and the strong brominating power with some tolerance against H2O2. Its production mechanism was explained as the ionic reaction involving the protonated intermediate of AcOOH by kinetic analysis.
- China, Hideyasu,Okada, Yutaka,Ogino, Hiroyasu
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- Molecular cloning, structure, and reactivity of the second bromoperoxidase from Ascophyllum nodosum
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The sequence of bromoperoxidase II from the brown alga Ascophyllum nodosum was determined from a full length cloned cDNA, obtained from a tandem mass spectrometry RT-PCR-approach. The clone encodes a protein composed of 641 amino-acids, which provides a mature 67.4 kDa-bromoperoxidase II-protein (620 amino-acids). Based on 43% sequence homology with the previously characterized bromoperoxidase I from A. nodosum, a tertiary structure was modeled for the bromoperoxidase II. The structural model was refined on the basis of results from gel filtration and vanadate-binding studies, showing that the bromoperoxidase II is a hexameric metalloprotein, which binds 0.5 equivalents of vanadate as cofactor per 67.4 kDa-subunit, for catalyzing oxidation of bromide by hydrogen peroxide in a bi-bi-ping-pong mechanism (kcat = 153 s-1, 22 °C, pH 5.9). Bromide thereby is converted into a bromoelectrophile of reactivity similar to molecular bromine, based on competition kinetic data on phenol bromination and correlation analysis. Reactivity provided by the bromoperoxidase II mimics biosynthesis of methyl 4-bromopyrrole-2-carboxylate, a natural product isolated from the marine sponge Axinella tenuidigitata.
- Wischang, Diana,Radlow, Madlen,Schulz, Heiko,Vilter, Hans,Viehweger, Lutz,Altmeyer, Matthias O.,Kegler, Carsten,Herrmann, Jennifer,Mueller, Rolf,Gaillard, Fanny,Delage, Ludovic,Leblanc, Catherine,Hartung, Jens
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supporting information
p. 25 - 34
(2012/11/13)
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- The (Schiff base)vanadium(v) complex catalyzed oxidation of bromide - A new method for the in situ generation of bromine and its application in the synthesis of functionalized cyclic ethers
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(Schiff base)vanadium(v) complexes 5 with tridentate imine auxiliaries served as catalysts for the oxidation of Br with tert-butyl hydroperoxide (TBHP) in nonaqueous solvents. This reaction has been applied for the conversion of substituted 4-penten-1-ols into 5-exo-bromo-cyclized products, including a diastereomerically pure heterocyclic precursor used in a synthesis of the all-trans-configured 2,3,4,5-substituted tetrahydrofuran 2-epi-magnosalicin. Treatment of co-substituted bis(homoallylic) alcohols with the reagent combination of pyHBr, TBHP, and a vanadium(v) catalyst 5 afforded 6-endo-cyclized products, i.e. brominated tetrahydropyrans, as major compounds. The results from 51V NMR, ESI-MS, and supporting reactivity- selectivity studies indicated that the mechanism of the new bromination reaction consists of vanadium-dependent and vanadium-independent steps. A (Schiff base)vanadium(v) compound 5 is required for activation of TBHP via in situ formation of the corresponding tert-butylperoxy complex. This reagent oxidizes Br-, which under the reaction conditions provides Br2 as the active brominating reagent. The molecular bromine generated thus is released into the solution at a steady rate and serves as a reagent for the synthesis of β-brominated cyclic ethers from bis(homoallylic) alcohols in a second, vanadium-independent step. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Greb, Marco,Hartung, Jens,Koehler, Franz,Spehar, Kristina,Kluge, Ralph,Csuk, Rene
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p. 3799 - 3812
(2007/10/03)
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- First detection of a chloroperoxidase in bryophytes
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Chlorinated cyclic bisbibenzyls of the isoplagiochin type are the first verified halometabolites from bryophytes. They could be obtained by in vitro chlorination of isoplagiochin C with chloroperoxidase from Caldariomyces fumago. Furthermore, an enzyme of
- Speicher, Andreas,Heisel, Ronny,Kolz, Juergen
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p. 679 - 682
(2007/10/03)
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