Study and quantification of the enantiodiscrimination power of four polymeric chiral LLCs using NAD 2D-NMR

Abstract

Identifying and understanding the role of key molecular factors involved in the orientation/discrimination phenomena of analytes in polymer-based chiral liquid crystals (CLCs) are essential tasks for optimizing computational predictions (molecular...

Residual‐Chemical‐Shift‐Anisotropy‐Based Enantiodifferentiation in Lyotropic Liquid Crystalline Phases Based on Helically Chiral Polyacetylenes

“…[10d-f,12c-e,13b,15] These media are chiral LLC phases derived from various polymers such as poly-γbenzyl-L/D-glutamate (PBLG/PBDG), [10d,11,16] poly-γ-ethyl-L/ (PPAs). [12,20] Except for PBLG, most of the alignment media induce sufficiently weak alignment to deliver simple extraction of RDCs. The RDCs of several analytes were measured in these media demonstrating their enantiodiscrimination capabilities.…”

Anisotropic 1H STD‐NMR Spectroscopy: Exploration of Enantiomer‐Polypeptide Interactions in Chiral Oriented Environments

“…These NMR interactions have been successfully exploited in structural/conformational studies, in the determination of 3D structures, relative configurations [7–10] or in the measurement of enantiomeric excesses, … [1,2] However, the underlying principles governing the enantio‐discrimination mechanisms, i. e. the difference between $${{\langle {S}_{{\rm \alpha }{\rm \beta }}\rangle }^{R}}$$ and $${{\langle {S}_{{\rm \alpha }{\rm \beta }}\rangle }^{S}}$$ , are still under investigation [11–13] …”

“…Previous studies have assessed and compared the enantio‐discrimination either for a given chiral solute in regards to various polymeric‐based CLCs, or rather for a collection of analytes dissolved in similar mesophases. This can be evaluated by measuring the local differential ordering effect (DOE) using selectively deuterated analytes [24] or at a more global level by comparing $${{\langle {S}_{{\rm \alpha }{\rm \beta }}\rangle }^{R,S}}$$ for both enantiomers (variation of principal axis direction, 9D angle, …) determined using anisotropic data such as ( 1 H‐ 1 H)‐RDC, ( 13 C‐ 1 H)‐RDC and more recently 2 H‐RQC [1,2,6,11] . While more comprehensive and reliable, this approach is sometimes time‐consuming and requires a sufficient amount of anisotropic data to determine the Saupe's matrices, $${{\langle {S}_{{\rm \alpha }{\rm \beta }}\rangle }^{R,S}}$$ , (over 5 for C 1 ‐symmetry chiral molecules) [25]…”

“…These NMR interactions have been successfully exploited in structural/conformational studies, in the determination of 3D structures, relative configurations [7][8][9][10] or in the measurement of enantiomeric excesses, … [1,2] However, the underlying principles governing the enantio-discrimination mechanisms, i. e. the difference between hS ab i R and hS ab i S , are still under investigation. [11][12][13] This understanding is of major importance for: i) determining the absolute configuration of stereogenic centers from NMR residual anisotropic data (RDC, RCSA, RQC) supported by computational simulations (molecular dynamics), [14][15][16][17][18] ii) designing the structure of new efficient polymeric-based lyotropic liquid crystals, e. g. choice of the polymer, [19][20][21][22] or iii) optimizing the choice of the co-solvent (polarity), the sample component concentration, the presence or not of additives, [23] to enhance the enantio-discrimination abilities.…”

“…This can be evaluated by measuring the local differential ordering effect (DOE) using selectively deuterated analytes [24] or at a more global level by comparing hS ab i R;S for both enantiomers (variation of principal axis direction, 9D angle, …) determined using anisotropic data such as ( 1 H-1 H)-RDC, ( 13 C-1 H)-RDC and more recently 2 H-RQC. [1,2,6,11] While more comprehensive and reliable, this ap-proach is sometimes time-consuming and requires a sufficient amount of anisotropic data to determine the Saupe's matrices, hS ab i R;S , (over 5 for C 1 -symmetry chiral molecules). [25] Moreover, it is worth noting the average nature of these calculated tensors, which encompasses the orientational behavior of the chiral analyte both at the vicinity of the polymer ("bound" analyte) and in the bulk of the mesophase ("free" analyte).…”