Tailoring the Recognition Property of a 19F-Labeled Gallium-Based NMR Probe: The Influence of the Metal Center

NMR-Based Chiral Discrimination of Bulky Amines with a 19F-Tagged NNO Pincer Complex

Within pharmaceutical research, ensuring the enantiomeric purity of chiral compounds is critical. Specifically, chiral amines are a crucial category of compounds, due to their extensive therapeutic uses. However, the enantiomeric analysis of these compounds, particularly those with significant steric hindrance, remains a challenge. To address this issue, our research introduces a novel chiral 19F-tagged NNO palladium pincer probe, strategically engineered with an open binding site to accommodate bulky amines. This probe facilitates the enantiodifferentiation of such amines, as evidenced by the distinct 19F NMR signals generated by the enantiomers. Moreover, our findings highlight the probe's applicability in the chiral discrimination of various psychoactive substances, underscoring its potential for the identification of illegal stimulant use and contributing to forensic investigations.

Enantiospecific Analysis of Carboxylic Acids Using Cinchona Alkaloid Dimers as Chiral Solvating Agents

Cinchona alkaloid derivatives as Brønsted base catalysts have attracted considerable attention in the field of asymmetric catalysis. However, their potential application as chiral solvating agents has not been described. In this research, we investigated the use of the Cinchona alkaloid dimer, namely, (DHQ)2PHAL, as a chiral solvating agent for discerning various mandelic acid derivatives through 1H NMR spectroscopy. The addition of catalytic amounts of DMAP facilitated this process. Our experimental results demonstrate that dimeric (DHQ)2PHAL exhibits remarkable chiral discrimination properties regarding the diagnostic split protons of 1H NMR signals (including 24 examples, up to 0.321 ppm). Furthermore, it serves as an excellent chiral discriminating agent and provides good resolution for racemic chiral phosphoric acid as determined by 31P NMR spectroscopy. The quality of enantiodifferentiation has also been evaluated by means of the parameter "resolution (Rs)". Significantly, this class of CSAs based on (alkaloid)2linker systems with an azaaromatic linker can be directly employed, which is commercially available in an enantiopure form at very low cost and exhibits promising potential in determining the enantiopurity of α-hydroxy acids by chemoselective and biocatalytic reactions.

A high-performance chiral 19F-labeled probe with an increased structural twisting

We developed a new strategy to enhance the chiral discrimination capability of 19F-labeled probes by tuning the torsion angle of the probe's backbone, allowing for the resolution of challenging analytes. Its versatility is demonstrated through the superior performance and the wide analyte scope.

Detection and Identification of Nitrile Compounds via Recognition-Enabled Chromatographic 19F NMR

The surge in applications of nitrile compounds across diverse fields, such as pharmaceuticals, agrochemicals, dyes, and functional materials, necessitates the development of rapid and efficient detection and identification methods. In this study, we introduce a chemosensing strategy employing a novel 19F-labeled probe, facilitating swift and accurate analysis of a broad spectrum of nitrile-containing analytes. This approach leverages the reversible interaction between the 19F-labeled probe and the analytes to produce chromatogram-like outputs, ensuring the precise identification of various pharmaceuticals and pesticides within complex matrices. Additionally, this dynamic system offers a versatile platform to investigate through-space 19F-19F interactions, showcasing its potential for future applications in mechanistic studies.

Bioinspired Fluorine Labeling for 19F NMR-Based Plasma Amine Profiling

Metabolite profiling serves as a powerful tool that advances our understanding of biological systems, disease mechanisms, and environmental interactions. In this study, we present an approach employing 19F-nuclear magnetic resonance (19F NMR) spectroscopy for plasma amine profiling. This method utilizes a highly efficient and reliable fluorine-labeling reagent, 3,5-difluorosalicylaldehyde, which effectively emulates pyridoxal phosphate, facilitating the formation of Schiff base compounds with primary amines. The fluorine labeling allows for distinct resolution of 19F NMR signals from amine mixtures, leading to precise identification and quantification of amine metabolites in human plasma. This advancement offers valuable tools for furthering metabolomics research.

Chiral Discrimination of Acyclic Secondary Amines by 19F NMR

Chiral aliphatic amine compounds exhibit a range of physiological activities, making them highly sought-after in the pharmaceutical industry and biological research. One notable obstacle in studying these compounds stems from the pronounced steric hindrance surrounding the nitrogen atom. This characteristic often leads to a weak affinity of acyclic secondary amines for molecular probes, making their chiral discrimination intricate. In response to this challenge, our research has unveiled a novel 19F-labeled probe adept at recognizing and distinguishing between enantiomers of these acyclic secondary amines. By strategically incorporating a single fluorine atom as the 19F label, we have managed to diminish the steric hindrance at the binding site. This alteration bolsters the probe's affinity toward bulkier analytes. As a testament to its effectiveness, we have successfully employed our probe in the chiral analysis of relevant pharmaceuticals, accurately determining their enantiocomposition.

Chiral Discrimination of Monosaccharides Derivatized with 2-Fluorophenyl Hydrazine Using 19F NMR Spectroscopy

Chiral discrimination of monosaccharides holds significant importance, especially given the growing interest of the pharmaceutical industry in their utilization. However, the majority of existing methods has predominantly centered around chromatographic techniques. In this study, we introduce a 19F NMR-based comprehensive approach for chiral analysis specifically tailored for 15 pairs of aldoses. This technique involves employing sugar hydrazones containing fluorine in combination with chiral octahedral gallium and scandium complexes. By utilizing highly sensitive 19F NMR spectroscopy, the fluorine label in the sugar hydrazone enables accurate differentiation between d and l enantiomers. The efficiency of the newly developed method was demonstrated through its successful application in both quantitative and qualitative analyses of mixtures containing various monosaccharides.

Chiral Discrimination of Nitrile Compounds Using a 19F-Labeled Palladium Probe

This study presents a ¹⁹F-labeled cyclopalladium probe for the rapid discrimination of chiral nitriles in pharmaceuticals, natural products, and agrochemicals. The probe binds reversibly to chiral nitriles, generating distinct ¹⁹F nuclear magnetic resonance signals for each enantiomer and enabling quick determination of enantiocomposition. The method allows for simultaneous detection of seven pairs of enantiomeric nitriles and application in assessing the enantiomeric excess of an asymmetric C-H cyanation reaction.