Séminaire PTF RMN | Philipe Lesot "The essentiality of recent anisotropic NMR spectroscopy"

Developing new analytical approaches or specific tools for studying chiral or prochiral molecules by multinuclear NMR is a modern and exciting challenge for spectroscopists.^1,2 By relying solely on isotropic NMR observables (diso, J, nOe), NMR in liquids is sometimes insufficient to gain access to certain molecular information that can, alternatively, be appropriately revealed using residual anisotropic NMR interactions. These order-dependent NMR interactions (which average out to zero in liquids) are explicitly detected in NMR spectra of solutes recorded in low-alignment solvents such as lyotropic liquid crystals (chiral or not), which still allow high-resolution spectral signatures to be obtained.

In practice, solutes dissolved in aligning environments exhibit a molecular orientational order (on average) that leads to the measurement of residual chemical shift anisotropies (¹³C-RCSA), residual ¹³C-¹H dipolar couplings (¹³C-¹H)-RDC) or residual ²H quadrupolar couplings (²H-RQC), for instance. Advantageously, if the oriented medium is chiral, spectral enantiodiscrimination of the enantiomers can be performed.

In this talk, we will describe several recent methodologies, and key analytical applications of chiral anisotropic NMR based on the orientational properties of  organic solutions  of  polypeptide- and/or polyacetylene-based helically chiral polymers.³ Particular attention will be paid to chiral bioactive molecules.

References:

1) P. Lesot, C. Aroulanda, H. Zimmermann, Z. Luz, Chem. Soc. Rev., 2015, 44, 230–275.
2) P. Lesot, C. Aroulanda, P. Berdagué, A. Meddour D. Merlet, J. Farjon, N. Giraud, O. Lafon, Prog. Nucl. Magn. Reson. Spectrosc., 2020, 116, 85–154.
3) C. Aroulanda, P. Lesot, Chirality, 2022, 34, 182–244.