Chiral Discrimination in the 13C and 2H NMR of the Crown and Saddle Isomers of Nonamethoxy−Cyclotriveratrylene in Chiral Liquid−Crystalline Solutions

We report 2H and 13C NMR spectra of the crown and saddle isomers of nonamethoxy−tribenzocyclononene (1), dissolved in lyotropic achiral and chiral liquid−crystalline solutions based on poly−−benzyl−glutamate and poly−−benzyl−L−glutamate (PBG and PBLG). The 2H−{1H} measurements include spectra of compound 1 deuterated in the ring methylene and in the aromatic sites as well as of the methyl groups in natural abundance. Carbon−13 spectra were recorded in natural abundance as well as in two isotopomers enriched in the ring methylene and one of the methoxy groups. The crown isomer (c−1) is rigid with C3 symmetry and can be separated into its enantiomers using a chiral high−performance liquid chromatography column. The NMR spectra of racemic c−1 in PBLG solutions exhibit two sets of lines due to the enantiomers. The peaks were identified by comparing the spectra with those of the neat enantiomers. Analysis of the 2H quadrupolar splittings and the 13C residual chemical shift anisotropies shows that the dominant factor determining the chiral discrimination is the difference in the ordering of the two enantiomers in the chiral liquid crystals. The saddle isomer (s−1) is highly flexible, undergoing fast pseudorotation between six conformers. Th