Institute of Food Chemistry (170b), University of Hohenheim, Garbenstr. 28, D-70599 Stuttgart, Germany.
Chemosphere. 2011 May;83(7):948-54. doi: 10.1016/j.chemosphere.2011.02.038. Epub 2011 Mar 12.
The 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (Q1, MBP-79) and further halogenated 1'-methyl-1,2'-bipyrroles (MBPs) are a class of marine natural products repeatedly detected in seafood and marine mammals from all over the world. Only Q1 is currently commercially available as reference standard and the full synthesis of mixed brominated-chlorinated compound is rather complicated. For this reason, synthetic Q1 (240 mg) was transferred into bromine-containing MBPs by UV-irradiation in the presence of bromine. Bromine, which rapidly vanished from the solutions, was renewed during the reaction in order to generate higher amounts of Br-containing MBPs. A total of ∼150 mg Q1 was transferred after ∼10 min irradiation with high amounts of Br(2) to give 30.5mg BrCl(6)-MBPs along with lower proportions of Br(2)Cl(5)-, Br(3)Cl(4)-, Br(4)Cl(3)- and traces of Br(5)Cl(2)-MBPs. Longer UV-irradiation in the presence of Br(2) even allowed for the detection of Br(6)Cl-MBPs and traces of Br(7)-MBP. However, this reaction also provided some unknown by-products. A sample stored in the dark and later in in-door light (no UV irradiation) also eliminated Q1 after 76 d in favour of heptahalogenated MBPs with up to three bromine substituents. The irradiation products were separated on silica, and fractions containing only Q1 and BrCl(6)-MBPs were then further fractionated by non-aqueous RP-HPLC. A pure isolate of the major BrCl(6)-MBP (∼1.5mg) was characterized by GC/MS and (13)C NMR to be 2-bromo-3,3',4,4',5,5'-hexachloro-1-methyl-1,2'-bipyrrole (Br-MBP-75). Partial GC enantioseparation of the axially chiral Br-MBP-75 was achieved on a β-PMCD column. A full enantioseparation was managed by enantioselective HPLC using a NUCLEOCEL DELTA S column. Low amounts of pure BrCl(6)-MBP enantiomers could be trapped.
2,3,3',4,4',5,5'-七氯-1'-甲基-1,2'-联吡咯（Q1，MBP-79）和进一步卤代的 1'-甲基-1,2'-联吡咯（MBPs）是一类在世界各地的海鲜和海洋哺乳动物中反复检测到的海洋天然产物。目前只有 Q1 可作为参考标准商业化，而混合溴代-氯代化合物的全合成相当复杂。因此，通过在溴存在下用紫外线照射，将合成的 Q1（240mg）转化为含溴的 MBPs。溴迅速从溶液中消失，在反应过程中不断补充，以生成更多的含 Br 的 MBPs。在高浓度 Br₂存在下照射约 10 分钟后，共转化了约 150mg 的 Q1，得到 30.5mg 的 BrCl₆-MBPs，同时还生成了较低比例的 Br₂Cl₅-MBPs、Br₃Cl₄-MBPs、Br₄Cl₃-MBPs 和痕量的 Br₅Cl₂-MBPs。在 Br₂存在下进行更长时间的紫外线照射甚至可以检测到 Br₆Cl-MBPs 和痕量的 Br₇-MBP。然而，该反应也提供了一些未知的副产物。一个保存在暗处，后来放在室内光线下（没有紫外线照射）的样品在 76 天后也消除了 Q1，有利于形成具有多达三个溴取代基的七卤代 MBPs。照射产物在硅胶上分离，仅含有 Q1 和 BrCl₆-MBPs 的馏分然后通过非水反相 HPLC 进一步分离。主要的 BrCl₆-MBP（约 1.5mg）的纯分离物通过 GC/MS 和 (13)C NMR 鉴定为 2-溴-3,3',4,4',5,5'-六氯-1-甲基-1,2'-联吡咯（Br-MBP-75）。在 β-PMCD 柱上对轴手性 Br-MBP-75 进行了部分 GC 对映体拆分。通过使用 NUCLEOCEL DELTA S 柱的对映选择性 HPLC 实现了完全的对映体拆分。可以捕获到少量的纯 BrCl₆-MBP 对映体。
