Enantioseparation of ondansetron by countercurrent chromatography using sulfobutyl ether-β-cyclodextrin as chiral selector

Theoretical study of modified multiple dual-mode elution counter-current chromatography based on chiral separation

The fact that both phases are liquids makes it simple to implement counter-current chromatography (CCC), which involves alternating elution modes and phase roles during the separation process. Using two distinct multiple dual-mode (MDM) elution techniques for chiral separation, the team demonstrated a superior separation effect in a prior study. When selecting a chiral selector with high enantiomer recognition capability is difficult, the separation efficiency of the CCC column can be enhanced through multiple cycles. This approach facilitates the preparation of enantiomers that are challenging to isolate under classical CCC conditions. A straightforward mathematical model was created in this study to forecast the number of cycles and the mode conversion time needed for the separation process after the modified MDM method was further examined theoretically. After modeling molecules, the theoretical model was confirmed, and the outcomes generally agreed with the calculations from the theoretical model. This offers substantial support for the modified MDM method's real-world implementation in chiral separation.

Impact of the degree of substitution on the enantioseparation of anionic β-cyclodextrin in liquid‒liquid extraction and countercurrent chromatography: Insights from molecular docking simulations

Five types of sulfobutylether-β-cyclodextrin (SBE-β-CD) and carboxymethyl-β-cyclodextrin (CM-β-CD) with different degrees of substitution were synthesized, and six and five racemates were respectively chosen to study the influence of the degree of substitution on the enantioseparation factor. The synthesized SBE-β-CD and CM-β-CD were characterized using 1H NMR spectroscopy and mass spectrometry. The results indicated that the influence of the degree of substitution on enantioseparation for distinct racemates exhibited significant variability. Increasing the degree of substitution of CM-β-CD led to an increasing enantioseparation factor, while SBE-β-CD with a specific degree of substitution provided the optimum enantioseparation factor for some racemates. The optimum enantioseparation factors of N-methyl duloxetine and duloxetine were obtained when a relatively low degree of substitution (DS = 3.5) was selected. And the optimum enantioseparation factor was obtained with a relatively high degree of substitution (DS = 7.5). SBE-β-CD with a low substitution degree of 3.5 was chosen to optimize the countercurrent chromatographic enantioseparation of N-methyl-duloxetine, which resulted in a significant improvement in peak resolution from 0.51 to 0.83. Molecular docking was used to construct three SBE-β-CDs with different degrees and distributions of substitution, and a good agreement was found between the docking results and the experimental results.

Recent advances in chiral selectors immobilization and chiral mobile phase additives in liquid chromatographic enantio-separations: A review

For decades now, the separation of chiral enantiomers of drugs has been gaining the interest and attention of researchers. In 1991, the first guidelines for development of chiral drugs were firstly released by the US-FDA. Since then, the development in chromatographic enantioseparation tools has been fast and variable, aiming at creating a suitable environment where the physically and chemically identical enantiomers can be separated. Among those tools, the immobilization of chiral selectors (CS) on different stationary phases and the chiral mobile phase additives (CMPA) which have been progressed and studied extensively. This review article highlights the major advances in immobilization of CS together with their different recognition mechanisms as well as CMPA as a cheaper and successful alternative for chiral stationary phases. Moreover, the role of molecular modeling tool as a pre-step in the choice of CS for evaluating possible interactions with different ligands has been pointed up. Illustrations of reported methods and updates for immobilized CS and CMPA have been included.

Enantioseparation of N-methyl duloxetine, duloxetine and fluoxetine by countercurrent chromatography using anionic β-cyclodextrin as chiral selector

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An overview of chiral separations of pharmaceutically active substances by HPLC (2018-2020)

This review provides a brief survey of chiral separation of pharmaceutically active substances published over the last 3 years (2018-2020). Chiral separation of drugs is an important area of research. The control of enantiomeric purity and determination of individual enantiomeric drug molecules is a necessity especially for clinical, analytical, and regulatory purposes. Among chromatographic resolution methods, high-performance liquid chromatography based on chiral stationary phases remains the most popular and effective method used for chiral separation of various drugs. In this review, attention is paid to several classes of chiral stationary phases that have been the most frequently used for drug enantioseparation during this period.

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