Sulfated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

The utility of a series of sulfated cyclodextrins as water-soluble chiral NMR solvating agents for cationic substrates is described. Sulfated alpha-, beta- and gamma-cyclodextrin with degrees of substitution of 12, 13 and 14, respectively, a sulfated beta-cyclodextrin with a degree of substitution of 9 and a sulfobutyl ether beta-cyclodextrin with a degree of substitution of 63 are examined. Results with 33 water-soluble cationic organic salts are reported. Chiral differentiation with the sulfated cyclodextrins is compared to prior results obtained with anionic carboxymethylated and phosphated cyclodextrins. The highly sulfated cyclodextrins are often more effective at causing enantiomeric differentiation in H-1 NMR spectra than the sulfobutyl ether, carboxymethylated and phosphated cyclodextrins, and are recommended as the first choice of a chiral solvating agent for the analysis of chiral cationic organic salts in aqueous solution. (C) 2017 Elsevier Ltd. All rights reserved.