Bis-quinolinium cyclophanes: toward a pharmacophore model for the blockade of apamin-sensitive SKCa channels in sympathetic neurons

The synthesis, pharmacological evaluation, and molecular modeling studies of unsymmetrical bis-alkylene bis-quinolinium cyclophanes and xylylene–alkylene bis-quinolinium cyclophanes is described. Two important structural features of the pharmacophore for SKCa channel blockade have been identified. These are (i) an optimum distance of ca. 5.8 Å between the centroids of the pyridinium rings of the two quinolinium groups and (ii) a preference for conformations having the quinolinium groups in a synperiplanar orientation.