title: Bromination of 2-methoxydiphenyl ether to an average of tetrabrominated 2-methoxydiphenyl ethers.
abstract: Brominated 2-phenoxyanisoles (2-methoxydiphenyl ethers, 2-MeO-BDEs) are a class of halogenated natural products, produced by algae and sponges. Especially two tetrabrominated isomers, i.e. 2'-MeO-BDE 68 (BC-2) and 6-MeO-BDE 47 (BC-3), have also been frequently determined in environmental and food samples. In addition, 2-MeO-BDEs are under discussion as metabolites of polybrominated diphenyl ethers (PBDEs). In this study, we synthesized the backbone 2-methoxydiphenyl ether and brominated it to an average degree of four bromine substituents. The reaction mixture only contained one major product (∼90%) along with three further MeO-BDEs and ∼5% hydroxylated BDEs. In all likelihood, the HO-BDEs were formed in a side reaction by cleavage of the methoxy group. The major MeO-BDE was identified as 6'-methoxy-2,3',4,4'-tetrabromodiphenyl ether (6'-MeO-BDE-66). The HO-BDEs were separated by KOH/n-hexane partitioning, and the resulting 2-MeO-BDEs were fractionated by means of high-speed counter-current chromatography (HSCCC). Due to the excellent enrichment facilities of HSCCC, some 15 MeO-BDEs, mainly present at traces only, could be detected in 26 fractions, and eight of them could be characterized by nuclear magnetic resonance spectroscopy (NMR). Only two of the compounds--2'-MeO-BDE 68 and 6-MeO-BDE 123--had been characterized as natural products while the prominent halogenated natural product 6-MeO-BDE 47 was not detected at all in the reaction product. The "non-natural" 2-MeO-BDEs may be useful internal standards in trace analysis.
authors.affiliation: Institute of Food Chemistry (170b), University of Hohenheim, Garbenstr. 28, D-70599 Stuttgart, Germany. walter.vetter@uni-hohenheim.de
authors.forename: Walter
authors.initials: W
authors.lastname: Vetter
authors.forename: Jochen
authors.initials: J
authors.lastname: Kirres
authors.forename: Paul
authors.initials: P
authors.lastname: Bendig
mesh_terms: D003377:Countercurrent Distribution; D008401:Gas Chromatography-Mass Spectrometry; D055768:Halogenated Diphenyl Ethers / Q000737:chemistry*; D054879:Halogenation; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D010647:Phenyl Ethers / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D055768:Halogenated Diphenyl Ethers; D010647:Phenyl Ethers