Characterization of binding affinities in a chromatographic system by suspended state HR/MAS NMR spectroscopy

Abstract

In the current work a racemate of (R)- and (S)-benzylmandelate was separated with a stereoselective polysaccharide-based chiral stationary phase by HPLC. To elucidate the occurring chiral molecular recognition processes in the heterogeneous system used, NMR spectroscopy was chosen under high resolution/magic angle spinning (HR/MAS) NMR conditions in the suspended state. Therefore, and as a proof of concept, a combination of several NMR methods such as spin-lattice relaxation time (T(1)) measurements (T(1)), the saturation transfer difference, and the 2D experiment of the transferred nuclear overhauser enhancement spectroscopy technique were applied. With HR/MAS NMR it is feasible to combine NMR and chromatography to achieve further insights into the separation process.

Fundamental Developments of Chiral Phase Chromatography in Connection with Enantioselective Synthesis of β‐Amino Acids

“…Important clues of the role of carbonyl functional groups in cellulose esters pointed out that these constitute the main binding chiral sites, which can interact with racemic compounds through hydrogen bonding and dipole‐dipole interactions for chiral discrimination ,. Over the course of the years, a highly refined understanding about the chiral recognition mechanism performed by polysaccharides derivatives has been achieved through detailed studies combining diverse techniques,, such as NMR spectroscopy, solid state NMR, attenuated total reflectance infrared spectroscopy, vibrational circular dichroism, and electrostatic potential surfaces (EPSs) determined via Density Functional Theory (DFT) calculations, among others …”

Determination of the electronic and structural configuration of coordination compounds by synchrotron-radiation techniques

“…In order to induce transition among the different spin levels an oscillating electromagnetic field can be applied to the system. NMR spectroscopy [580][581][582][583][584][585][586] represents a powerful technique for structural investigation of metal complexes: the information provided by 1D spectra of NMR active metal nuclides as well as 1 H, 13 C, 15 As was the case of EXAFS technique (Section 2.5), the local nature of the magnetic interaction probed by NMR allows to obtain structural information also on samples characterized by a low crystallinity, such as amorphous materials and nanomaterials, where single crystal diffraction methods fail. There are indeed several cases where NMR has been crucial in determining the crystal structure; the specialized literature often refers to such studies as to "NMR crystallography" .…”

Elucidation of the Enantiodiscrimination Properties of a Nonracemic Chiral Alignment Medium through Gel‐based Capillary Electrochromatography: Separation of the Mefloquine Stereoisomers

“…However, since these times, the two areas have evolved increasingly independently. Although NMR studies are used to elucidate structural aspects of ES, the role of enantioselective chromatography as a versatile tool in the understanding of ED obtained in NMR has been largely neglected. Since the early report of Pirkle and Pochapsky in 1986, isotropic solution‐NMR studies have been used to investigate structural aspects of chromatographic enantiorecognition processes ,.…”