Liquid Chromatographic Enantioseparations Utilizing Chiral Stationary Phases Based on Crown Ethers and Cyclofructans

Abstract

Natural compounds can exist in different forms, where molecules possessing chirality play an essential role in living organisms. Currently, one of the most important tasks of modern analytical chemistry is the enantioseparation of chiral compounds, in particular, the enantiomers of compounds having biological and/or pharmaceutical activity. Whether the task is to analyze environmental or food samples or to develop an assay for drug control, well-reproducible, highly sensitive, stereoselective, and robust methods are required. High-performance liquid chromatography best meets these conditions. Nevertheless, in many cases, gas chromatography, supercritical fluid chromatography, or capillary electrophoresis can also offer a suitable solution. Amino acids, proteins, cyclodextrins, derivatized polysaccharides, macrocyclic glycopeptides, and ion exchangers can serve as efficient selectors in liquid chromatography, and they are quite frequently applied and reviewed. Crown ethers and cyclofructans possessing similar structural characteristics and selectivity in the enantiodiscrimination of different amine compounds are discussed less frequently. This review collects information on enantioseparations achieved recently with the use of chiral stationary phases based on crown ethers or cyclofructans, focusing on liquid chromatographic applications.

Macrocyclic glycopeptides- and derivatized cyclofructan-based chiral stationary phases for the enantioseparation of fluorinated ß-phenylalanine analogs

“…Enantioseparations on cyclofructan-based CSPs generally are carried out in normal-phase mode and PIM [22]. Taking the solubility of amino acids into consideration, separations were carried out in the PIM using MeOH/MeCN as a bulk solvent in the presence of TFA and TEA as acid and base additives.…”

“…Functionalized polysaccharides on SPP and FPP support were first applied by Chankvetadze et al [19], while Cinchona alkaloid-based mono-and zwitterionic CSPs applying SPPs and FPPs was developed by Armstrong et al [20] and Lämmerhofer et al [21], respectively. It is worth noting that in addition to the above citations, some very recent review papers have summarized these new results [22][23][24].…”

Chiral separation of dipeptides on Cinchona‐based zwitterionic chiral stationary phases under buffer‐free reversed‐phase conditions

“…Chiral resolution of various peptides has recently been reviewed 9 . It has been documented that almost all CSPs, which are currently commercially available, can be utilized for this purpose, including polysaccharides, 10 cyclodextrines, 11 crown ethers, 12 and zwitterion ion exchangers 13 . The latter CSPs (commercially available as Chiralpak ZWIX (+) and Chiralpak ZWIX (−)) have shown certain advantages in this field; however, they can be used also for other classes of ionizable substances (acids and bases) 14 .…”

Analytical Separation of Closantel Enantiomers by HPLC

“…To date, few studies have investigated the chiral separation of closantel enantiomers using HPLC [ 14 ]. This research aimed to develop analytical separations of closantel enantiomers using the normal-phase (NP) HPLC mode with different types of chiral selectors such as tris carbamates of amylose polysaccharides [ 15 , 16 ], isopropyl carbamates of cyclofructans [ 17 , 18 , 19 ], and β-cyclodextrins derivatives [ 20 ]. Filling the gap in the analytical separation of racemic drugs has great significance for the chemical, pharmaceutical, and biological fields.…”