34649-20-2Relevant academic research and scientific papers
Vanadate-dependent bromoperoxidases from Ascophyllum nodosum in the synthesis of brominated phenols and pyrroles
Wischang, Diana,Radlow, Madlen,Hartung, Jens
, p. 11926 - 11940 (2013)
Bromoperoxidases from the brown alga Ascophyllum nodosum, abbreviated as VBrPO(AnI) and VBrPO(AnII), show 41% sequence homology and differ by a factor of two in the percentage of α-helical secondary structures. Protein monomers organize into homodimers for VBrPO(AnI) and hexamers for VBrPO(AnII). Bromoperoxidase II binds hydrogen peroxide and bromide by approximately one order of magnitude stronger than VBrPO(AnI). In oxidation catalysis, bromoperoxidases I and II turn over hydrogen peroxide and bromide similarly fast, yielding in morpholine-4-ethanesulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) molecular bromine as reagent for electrophilic hydrocarbon bromination. Alternative compounds, such as tribromide and hypobromous acid are not sufficiently electrophilic for being directly involved in carbon-bromine bond formation. A decrease in electrophilicity from bromine via hypobromous acid to tribromide correlates in a frontier molecular orbital (FMO) analysis with larger energy gaps between the π-type HOMO of, for example, an alkene and the σ*Br,X-type LUMO of the bromination reagent. By using this approach, the reactivity of substrates and selectivity for carbon-bromine bond formation in reactions mediated by vanadate-dependent bromoperoxidases become predictable, as exemplified by the synthesis of bromopyrroles occurring naturally in marine sponges of the genera Agelas, Acanthella, and Axinella. The Royal Society of Chemistry.
Parameters for bromination of pyrroles in bromoperoxidase-catalyzed oxidations
Wischang, Diana,Hartung, Jens
experimental part, p. 4048 - 4054 (2011/06/27)
Ester-, cyano-, and carboxamide-substituted 1H-pyrroles undergo electrophilic aromatic bromination, if treated with hydrogen peroxide and sodium bromide at pH 6.2 and 20 °C. Oxidation of bromide under such conditions is catalyzed by a vanadate(V)-dependent bromoperoxidase, in a substrate/enzyme ratio of 32-63 μmol %. To obtain maximum yields of bromopyrroles (up to 91%) by spending least amount of substrates and catalyst, hydrogen peroxide and sodium bromide have to be added continuously to the enzyme and the 2-acceptor-substituted pyrrole (1.5 mmol) in a solution of morpholine-4- ethanesulfonic acid buffer. This technique was applied to prepare two marine natural products under biomimetic conditions, that is, methyl 4,5-dibromopyrrole-2-carboxylate (from Agelas oroides) and 4,5-dibromopyrrole-2- carboxamide (from Acanthella carteri).
