R-VAPOL-phosphoric acid based 1H and 13C-NMR for sensing of chiral amines and acids

R-VAPOL-chiral solvating agent for discrimination of chiral amines and acids using 1H and 13C NMR.

Enantiodiscrimination Using a Chiral Crown Ether as a Chiral Solvating Agent Using NMR Spectroscopy

For enantiomer separation of a variety of chiral compounds, a number of chiral selectors have been developed and applied. Among these chiral selectors are chiral crown ethers, a class of synthetic polyether molecules that bind protonated chiral primary amines with high selectivity. This article focuses on enantiodiscrimination using (18-crown-6)-2,3,11,12-tetracarboxylic acid as a crown ether-type chiral solvating agent for nuclear magnetic resonance spectroscopic method in several chirotechnologies.

Enantiomeric NMR discrimination of carboxylic acids using actinomycin D as a chiral solvating agent

We extended actinomycin D as a practical CSA for rapid enantiomeric determination of chiral carboxylic acids by1H NMR spectroscopy.

Correction: Enantiomeric NMR discrimination of carboxylic acids using actinomycin D as a chiral solvating agent

Correction for ‘Enantiomeric NMR discrimination of carboxylic acids using actinomycin D as a chiral solvating agent’ by Liwen Bai, et al., Org. Biomol. Chem., 2019, 17, 1466–1470.

One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination

The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons.

Optically pure 2-(quinolin-8-yloxy)cyclohexan-1-ol as a practical agent for molecular recognition by NMR and fluorescence spectroscopy

Optically pure 2-(quinolin-8-yloxy)cyclohexan-1-ol 1, obtained via simple chemical and bio-catalytic steps, was used as a chiral solvating agent for molecular recognition of the enantiomers of acids.