Brotin Thierry, Vanthuyne Nicolas, Cavagnat Dominique, Ducasse Laurent, Buffeteau Thierry
Laboratoire de Chimie de l'ENS Lyon (UMR 5182-CNRS), École Normale Supérieure de Lyon , 46 Allée d'Italie, 69364 Lyon, France.
J Org Chem. 2014 Jul 3;79(13):6028-36. doi: 10.1021/jo500621g. Epub 2014 Jun 16.
Enantiopure cryptophane derivatives bearing nine (2, 3) and 12 (4) methoxy substituents attached on the six aromatic rings were separated by HPLC using chiral stationary phases. The chiroptical properties of compounds 2-4 were determined from polarimetry, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) experiments and were compared to those of cryptophane-A (1) derivative. ECD spectra of 1 and 4 were calculated by time-dependent density functional theory (TDDFT) to determine the absolute configuration (AC) of cryptophane derivatives. The (+)-PP absolute configuration was thus established for the anti-cryptophane-A (1) and its congeners 2 and 4. VCD experiments associated with DFT calculations confirmed the (+)-PP configuration of anti-compounds 2 and 4 and established the (+)-PM configuration of the syn-3 compound as well. This study revealed the preferential all-trans (TTT) conformation of the three ethylenedioxy linkers for the CHCl3@1, CHCl3@3, and CHCl3@4 complexes, whereas the GTT conformation was found the most favorable for the CHCl3@2 complex.
通过使用手性固定相的高效液相色谱法，分离出了在六个芳香环上带有九个（2,3）和十二个（4）甲氧基取代基的对映体纯隐色体衍生物。通过旋光法、电子圆二色性（ECD）和振动圆二色性（VCD）实验测定了化合物2-4的手性光学性质，并与隐色体-A（1）衍生物的性质进行了比较。通过含时密度泛函理论（TDDFT）计算了1和4的ECD光谱，以确定隐色体衍生物的绝对构型（AC）。因此确定了反式隐色体-A（1）及其同系物2和4的（+）-PP绝对构型。与DFT计算相关的VCD实验证实了反式化合物2和4的（+）-PP构型，并确定了顺式-3化合物的（+）-PM构型。该研究揭示了对于CHCl3@1、CHCl3@3和CHCl3@4配合物，三个乙二氧基连接体优先采用全反式（TTT）构象，而对于CHCl3@2配合物，发现GTT构象最有利。
