Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University in Prague, Albertov 2030, 12843 Prague 2, Czech Republic.
J Chromatogr A. 2011 Mar 11;1218(10):1393-8. doi: 10.1016/j.chroma.2011.01.023. Epub 2011 Jan 15.
Derivatized cyclofructans have been recently introduced as a new class of chiral selectors with great application potential. In this study, a R-naphthylethyl-functionalized cyclofructan 6 based chiral stationary phase (RN CF6 CSP) was used for separation of substituted binaphthyl catalysts in the normal phase HPLC mode. Dominant interaction types that play a role in the separation mechanism were revealed by a linear free energy relationship (LFER) method. In order to evaluate the contribution of the substituent on the cyclofructan structure to retention, the R-naphthylethyl-functionalized β-cyclodextrin (RN CD) CSP was chosen for comparison. Retention factors of 46 widely different solutes, with known solvation parameters, were determined on each of the columns under the same mobile phase compositions used for the enantiomeric separations. The LFER results showed that hydrogen bond acidity and polarity/polarizibility have the greatest impact on retention and enantioresolution on the RN CF6 CSP. The equal influence of the naphthylethyl substituent on the both CSPs was also confirmed while the effects of the basic cyclofructan versus cyclodextrin structures were different. The addition of trifluoroacetic acid to the hexane/propane-2-ol mobile phase was negligible on the RN CF6 CSP for the majority of atropoisomers except for one with ionizable functional groups. The RN CF6 column was shown to be more suitable for enantioseparation of the binaphthyl catalysts than the RN CD column. Higher retention offered by the latter CSP had no positive effect on the enantioresolution.
最近，衍生化环果糖已被引入作为一类具有巨大应用潜力的新型手性选择体。在本研究中，使用基于 R-萘乙基功能化的环果糖 6 的手性固定相（RN CF6 CSP）在正相 HPLC 模式下分离取代联萘基催化剂。通过线性自由能关系（LFER）方法揭示了在分离机制中起作用的主要相互作用类型。为了评估环果糖结构上取代基对保留的贡献，选择了 R-萘乙基功能化的β-环糊精（RN CD）CSP 进行比较。在相同的流动相组成下，在每个柱上测定了 46 种具有已知溶剂化参数的广泛不同的溶质的保留因子。LFER 结果表明，氢键酸度和极性/极化度对 RN CF6 CSP 的保留和对映体分辨率有最大影响。还证实了萘乙基取代基对两种 CSP 的同等影响，而基本环果糖与环糊精结构的影响不同。在大多数情况下，除了具有可离子化官能团的一种外，向正己烷/丙烷-2-醇流动相中添加三氟乙酸对 RN CF6 CSP 的影响可以忽略不计。与 RN CD 柱相比，RN CF6 柱更适合对联萘基催化剂的对映体分离。后者 CSP 提供的更高保留对对映体分辨率没有积极影响。
