Chiral sensors based on lipophilic cyclodextrins: interrogation of enantioselectivity by combined NMR, structural correlation and electrode response studies

Potentiometric chiral sensors based on ‘per’-O-octyl-α-cyclodextrin have been devised for the ephedrinium ion. Electrode response studies, varying the structure of the host cyclodextrin and of the guest β-arylammonium ion, combined with NMR measurements on the diastereoisomeric complexes have led to the formulation of a working model defining the structural origins of enantioselection in which the C-methyl substituent, β to the aryl ring, acts as a stereo-differentiating group, and residual hydroxy groups in the cyclodextrin are needed.