The adsorption of Naproxen enantiomers on the chiral stationary phase ()-Whelk-O1 under reversed-phase conditions: The effect of mobile phase composition

A comprehensive study to reveal the potential of a more sustainable ultra-high performance enantioselective reversed-phase chromatography on Pirkle-type stationary phase, with Whelk-O1 as a case study

In this study, we aimed to make enantioselective chromatography more sustainable, more sensitive, and compatible with aqueous formulations analysis and ESI-MS. To achieve this, we examined the effects of transitioning from normal-phase chromatography (which uses hydrocarbon-based solvents) to reversed-phase chromatography (using mobile phases based on water) using broad-spectrum Whelk-O1 columns as a critical study. For the first time, we holistically compared the thermodynamics and kinetics of the two elution modes in order to answer the question of whether same-column chemistry can effectively separate the compounds even in reversed-phase mode and found, unexpectedly, that reversed-phase chromatography using acetonitrile as the organic modifier was competitive from a kinetic standpoint. We also evaluated the effectiveness of three organic modifiers simultaneously on a sample of 11 molecules already resolved in NP conditions with different resolutions and achieved a resolution value of 1.5 for 91% and a resolution value of 2 for 82% of cases. Finally, we separated three racemates (within a k factor of 9) using only 480 µL of solvent per chromatographic run on a millibore column of 1 mm I.D., demonstrating that our approach allows for greener chromatographic separations.

Fundamentals of chirality, resolution, and enantiopure molecule synthesis methods

The chirality of molecules is a concept that explains the interactions in nature. We may observe the same formula but different organizations revolving around the chiral center. Since Pasteur's meticulous observation of sodium ammonium tartrate crystals' structure, scientists have discovered many features of chiral molecules. The number of newly approved single enantiomeric drugs increases every year and takes place in the market. Thus, separation or resolution methods of racemic mixtures are of continued importance in the efficacy of drugs, installation of affordable production processes, and convenient synthetic chemistry practice. This article presents the asymmetric synthesis approaches and the classification of direct resolution methods of chiral molecules.

Chiral derivatives of xanthones and benzophenones: Synthesis, enantioseparation, molecular docking, and tumor cell growth inhibition studies

Liquid chromatography enantioseparation and determination of enantiomeric purity of synthetized xanthone and benzophenone derivatives comprising one or more chiral moieties are reported. High enantioselectivity and resolution were observed in (S,S)‐Whelk‐O1 chiral stationary phase (CSP) for the enantiomeric mixtures of compounds comprising an aromatic ring linked to the stereogenic center(s), with α values ranging from 1.35 to 4.15 and Rs values ranging from 2.22 to 13.87. Among all the tested enantiomeric mixtures, those comprising three chiral moieties positioned in the xanthone scaffold gave the best chromatographic results. Enantiomers comprising an alkyl chain linked to the stereogenic centers were enantioseparated on a Lux® Celullose‐2 CSP. For both CSPs, the elution was performed in polar organic mode. The enantiomeric ratio (e.r.) values were always higher than 99%. Additionally, assessment of chiral recognition mechanisms on (S,S)‐Whelk‐O1 CSP was performed by molecular docking approach, which are in accordance with the chromatographic parameters. The nature and number of chiral moieties in the central aromatic scaffold of either xanthone or benzophenone derivatives are proved to be crucial for enantiorecognition. The evaluation of the growth inhibition of human tumor cell lines revealed that (S,S)‐(+)‐5 was the most potent compound, with values of GI50 of 12.83 ± 2.09 μM for A375‐C5 melanoma, 12.40 ± 1.16 μM for MCF‐7 breast adenocarcinoma, and 13.06 ± 1.29 μM for NCI‐H460 non‐small cell lung cancer. In some cases, the growth inhibitory effects demonstrated to be dependent on the stereochemistry of the compounds.

Chiral Stationary Phases for Liquid Chromatography: Recent Developments

The planning and development of new chiral stationary phases (CSPs) for liquid chromatography (LC) are considered as continuous and evolutionary issues since the introduction of the first CSP in 1938. The main objectives of the development strategies were to attempt the improvement of the chromatographic enantioresolution performance of the CSPs as well as enlarge their versatility and range of applications. Additionally, the transition to ultra-high-performance LC were underscored. The most recent strategies have comprised the introduction of new chiral selectors, the use of new materials as chromatographic supports or the reduction of its particle size, and the application of different synthetic approaches for preparation of CSPs. This review gathered the most recent developments associated to the different types of CSPs providing an overview of the relevant advances that are arising on LC.

Enantioresolution of chiral derivatives of xanthones on (S,S)-Whelk-O1 and L-phenylglycine stationary phases and chiral recognition mechanism by docking approach for (S,S)-Whelk-O1

The resolution of seven enantiomeric pairs of chiral derivatives of xanthones (CDXs) on (S,S)-Whelk-O1 and L-phenylglycine chiral stationary phases (CSPs) was systematically investigated using multimodal elution conditions (normal-phase, polar-organic, and reversed-phase). The (S,S)-Whelk-O1 CSP, under polar-organic conditions, demonstrated a very good power of resolution for the CDXs possessing an aromatic moiety linked to the stereogenic center with separation factor and resolution factor ranging from 1.91 to 7.55 and from 6.71 to 24.16, respectively. The chiral recognition mechanisms were also investigated for (S,S)-Whelk-O1 CSP by molecular docking technique. Data regarding the CSP-CDX molecular conformations and interactions were retrieved. These results were in accordance with the experimental chromatographic parameters regarding enantioselectivity and enantiomer elution order. The results of the present study fulfilled the initial objectives of enantioselective studies of CDXs and elucidation of intermolecular CSP-CDX interactions.