作者:Walter Vetter、Wu Jun
DOI:10.1021/ac025696o
日期:2002.8.1
A hexachloro congener (Q1-hex) of the natural heptachloro-1‘-methyl-1,2‘-bipyrrole Q1 was recently observed as a byproduct of the Q1 synthesis. NMR investigation confirmed that Q1-hex has a proton on a carbon in β-position to a nitrogen. Three isomers are possible that fulfill this prerequisite; unfortunately, however, the NMR data were not sufficient to distinguish among the three structural variants. Because only one isomer of Q1-hex is expected to be chiral, we utilized enantioselective gas chromatography and two chiral stationary phases to separate the atropisomers. Baseline separation of the Q1-hex atropisomers was obtained on 10% chemically bonded permethyl-β-cyclodextrin. In the full-scan mode, it was found that Q1-hex was racemic and that both atropisomers had identical mass fragmentation patterns. Partial resolution of the Q1-hex atropisomers was obtained on 25% tert-butyldimethylsilylated β-cyclodextrin diluted in PS086. In concert with previous NMR data, these enantioseparations prove that the structure of Q1-hex is 2,3,3‘,4‘,5,5‘-hexachloro-1‘-methyl-1,2‘-bipyrrole (5). To our knowledge, this is the first gas chromatographic separation of atropisomers of an axially chiral 1,2‘-bipyrrole derivative.
最近,在Q1合成的过程中,人们发现了一种六氯同系物(Q1-hex),它是天然七氯-1‘-甲基-1,2‘-联吡咯Q1的副产物。核磁共振(NMR)研究证实,Q1-hex在氮原子的β位碳上有一个质子。满足这一前提条件的异构体有三种;然而,遗憾的是,核磁共振数据不足以区分这三种结构变体。由于Q1-hex只有一个异构体是手性的,我们利用对映选择性气相色谱法和两种手性固定相分离了旋光异构体。在10%化学键合的全甲基-β-环糊精上获得了Q1-hex旋光异构体的基线分离。在全扫描