SERF-filtered experiments: new enantio-selective tools for deciphering complex spectra of racemic mixtures dissolved in chiral oriented media |
| |
Authors: | Farjon Jonathan Merlet Denis |
| |
Affiliation: | a Equipe de RMN en Milieu Orienté, ICMMO, UMR 8182, Bat. 410, Univ. Paris-Sud, 91405 Orsay Cedex, France |
| |
Abstract: | The use of chiral liquid crystals as NMR solvent is a powerful tool to visualize and quantify enantiomers. This technique is much more robust than traditional liquid state techniques. Recent developments have been performed to simplify proton spectra obtained in these solvents which are usually complex to analyze. In the different published sequences the enantiomeric differentiation can be visualized but none of them rely the different (1)H-(1)H couplings to have a coherent set for each enantiomer especially in cases of racemic mixtures. In this work to overcome such limitations, we present a new NMR pulse sequence using semi-selective pulses to assign for each enantiomer the different (1)H-(1)H couplings. The aim is to obtain the signal of only one enantiomer, through a first Selective ReFocussing (SERF) filtering block implemented for the enantio-selection followed by a second SERF block for measuring a chosen coupling. The whole sequence is called (1)H SERF-filtered-SERF. These techniques permit for the first time to assign all dipolar couplings to each enantiomer of racemic mixtures dissolved in chiral oriented media. We demonstrate that using this experiment it is possible to visualize enantio-differentiation even in the case where the multiplets are not resolved in the SERF experiments, pushing back the limits of the enantiomeric visualization. |
| |
Keywords: | Semi-selective pulses Enantio-selection PBLG chiral oriented media Selective refocusing experiments Racemic mixtures |
本文献已被 ScienceDirect PubMed 等数据库收录! |