Sulfated and carboxymethylated cyclodextrins and their lanthanide complexes as chiral NMR discriminating agents

Abstract

Sulfated and carboxymethylated cyclodextrins are effective at causing enantiomeric discrimination in the 1H NMR spectra of water-soluble organic cations. The anionic derivatives are more soluble in water than native cyclodextrins and the enantiomeric discrimination is usually larger than observed with native cyclodextrins. Lanthanide ions such as dysprosium(III) and ytterbium(III) associate at the anionic sulfonate and carboxymethylate groups and often cause considerable enhancements in the enantiomeric discrimination in the 1H NMR spectrum of the substrate. The enantiomeric discrimination caused by addition of lanthanide ions is large enough that much lower concentrations of the cyclodextrin can be used compared to conventional analyses with chiral solvating agents. Sulfated and carboxymethylated cyclodextrins are commercially available, which facilitates their use in NMR applications.