The enantiomeric separation of 4,5-disubstituted imidazoles by HPLC and CE using cyclodextrin-based chiral selectors
作者:Zachary S. Breitbach、Qing Feng、Panduka B. Koswatta、Edra Dodbiba、Carl J. Lovely、Daniel W. Armstrong
DOI:10.1080/10610278.2010.506545
日期:2010.11.1
to separate this set of compounds via CE. UsingHPLC, 14 of the 15 racemic compounds were separated. Eight of the analytes were separated using CE with resolutions up to 7.0. Using both HPLC and CE approaches, the entire set of analytes was separated. The optimisation of these separations was discussed and a comparison between the chiral selectors used was made. Lastly, the similarity of the 15 analytes
通过高效液相色谱 (HPLC) 和毛细管电泳 (CE) 检测了一系列 15 种外消旋 4,5-二取代咪唑化合物的对映体分离。这些生物碱分析物是天然产物钙卡定 A 和其他 Leucetta 衍生生物碱全合成的重要前体。因此,这些分析物的对映体分析不仅对生产纯对映体钙卡里定 A 很重要,而且对于更好地了解相关生物合成途径中涉及的立体化学也很重要。评估了几种键合环糊精(天然和衍生)固定相通过 HPLC 分离这些外消旋物的能力。同样,评估了几种环糊精衍生物通过 CE 分离这组化合物的能力。使用 HPLC,分离出 15 种外消旋化合物中的 14 种。使用 CE 分离了八种分析物,分辨率高达 7.0。使用 HPLC 和 CE 方法,可以分离整套分析物。讨论了这些分离的优化,并对所使用的手性选择器进行了比较。最后,15 种分析物的相似性有助于深入了解手性识别的机制。
Total Synthesis of (±)-Calcaridine A and (±)-<i>epi</i>-Calcaridine A
作者:Panduka B. Koswatta、Rasapalli Sivappa、H. V. Rasika Dias、Carl J. Lovely
DOI:10.1021/ol802018r
日期:2008.11.6
The first total synthesis of the Leucetta alkaloid calcaridine A is described based on a biosynthetic postulate. Application of an oxidative rearrangement of a 4,5-disubstituted imidazole leads to the formation of both calcaridine A and epi-calcaridine A. An X-ray crystal structure determination on the latter has allowed the assignment of the relative configuration of the epimeric natural product and calcaridine A by extrapolation.
Total Synthesis of the Leucetta-Derived Alkaloid Calcaridine A
A biomimetically guided total synthesis of the Leucetta-derived aminoimidazole alkaloid, calcaridine A, is described. The synthesis relies on position selective metalations of a 4,5-diiodoimidazole derivative to provide a tetrasubstituted imidazole. Subjection of this polysubstituted imidazole derivative to oxidative rearrangement with a Davis oxaziridine provides the corresponding imidazolone core of calcaridine A.