Enantiomeric analysis using natural abundance deuterium 3D NMR spectroscopy in polypeptide chiral oriented media

摘要

The use of natural abundance deuterium (NAD) three-dimensional (3D) NMR experiment in chiral liquid crystals (CLC) is reported and discussed. This homonuclear autocorrelation 3D experiment allows assigning deuterium signals of weakly aligned molecules at natural isotopic abundance. It provides an efficient strategy for identifying the spectral enantio-discriminations on NAD spectra. We demonstrate that NAD 3D NMR is feasible within reasonable experimental times (14 h) using the 3D Quadrupole Double-Quantum NMR sequence [O. Lafon, P. Lesot, Chem. Phys. Lett. 404 (2005) 90] and a 14.1 T NMR spectrometer equipped with a selective 5 mm deuterium NMR cryoprobe. The analytical potentialities of this technique are illustrated in the case of (+/-)-but-2-yn-1-ol dissolved in poly-c-benzyl-L-glutamate/CHCl3 mesophase.