Cyclodextrin Porous Liquid Materials for Efficient Chiral Recognition and Separation of Nucleosides

Porous liquids are porous materials that have exhibited unique properties in various fields. Herein, we developed a method to synthesize the type I porous liquids via liquefaction of cyclodextrins by chemical modification. The cyclodextrin porous liquids were characterized by Fourier-transform infrared (FTIR) spectroscopy, NMR, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS), circular dichroism (CD), and UV-vis spectroscopy. The measured ionic conductivity of the γ-cyclodextrin porous liquid was 500 times as great as that of its reactants, which was found to be the first instance with such great conductivity for a type I porous liquid. What is more, the γ-cyclodextrin porous liquid had been demonstrated experimentally to have outstanding chiral recognition ability toward pyrimidine nucleosides in water, which was further confirmed by computational simulations. Additionally, enantiomeric excess of the extracted nucleoside was achieved up to 84.81% by convenient extraction from the mixture of racemic nucleosides and γ-cyclodextrin porous liquid. The great features of the novel cyclodextrin porous liquids could bring opportunities in many fields, including the preparation of chiral separation materials, development of new drug screening mechanisms, and construction of chiral response materials.

Single isomer cyclodextrins as chiral selectors in capillary electrophoresis

Since decades, cyclodextrins are one of the most powerful selectors in chiral capillary electrophoresis for the enantioseparation of diverse organic compounds. This review concerns papers published over the last decade (from 2009 until nowadays), dealing with the capillary electrophoretic application of single isomer cyclodextrin derivatives in chiral separations. Following a brief overview of their synthetic approaches, the inventory of the neutral, negatively and positively charged (including both permanently ionic and pH-tunable ionizable substituents) and zwitterionic CD derivatives is presented, with insights to underlying structural aspects by NMR spectroscopy and molecular modeling. CE represents an ideal tool to study the weak, non-covalent supramolecular interactions. The published methods are reviewed in the light of enantioselectivity, enantiomer migration order and the fine-tuning of enantiodiscrimination by the substitution pattern of the single entity selector molecules, which is hardly possible for their randomly substituted counterparts. All the reviewed publications herein support that cyclodextrin-based chiral capillary electrophoresis seems to remain a popular choice in pharmaceutical and biomedical analysis.

A novel chiral electrochemiluminescence sensor that can discriminate proline enantiomers

A chiral stereoselective electrochemiluminescence (ECL) sensor was constructed by using Ru–AuNPs and β-CD–rGO composites to discriminate proline enantiomers.

Methoxyethylammonium monosubstituted β-cyclodextrin as the chiral selector for enantioseparation in capillary electrophoresis

Methoxyethylamine monosubstituted β-cyclodextrin, mono-6(A)-(2-methoxyethyl-1-ammonium)-6(A)-β-cyclodextrin chloride (MEtAMCD), is synthesized and analytically characterized. Bearing a methoxy group in cyclodextrin rim, MEtAMCD exhibits outstanding enantioselectivities toward ampholytic and acidic racemates in capillary electrophoresis. Driven by inclusion complexation, electrostatic interactions and/or hydrogen bonding, the enantioseparation of MEtAMCD is found to be strongly dependent on various separation parameters including buffer pH, cyclodextrin concentration, applied voltage, separation temperature and organic solvent additives. MEtAMCD demonstrates as a versatile cationic chiral selector for the studied 26 acidic and ampholytic enantiomers.