Complexation of dicarboxylates and phosphates by a semisynthetic alkaloid-based cyclophane in water

Dicationic N,N-dibenzylated cyclophane-type derivative 1 of a bisisoquinoline macrocyclic alkaloid, S,S-(+)-tetrandrine, was prepared and characterized. In aqueous solution 1 undergoes dimerization, which was studied by the concentration dependence of its H-1 NMR signals. The salt effect on the dimerization constant was analyzed by using different versions of Debye-Huckel-type equations. H-1 NMR titration of 1 by 10 dicarboxylate anions of different structures revealed strong peak binding selectivity for succinate in the series of alpha,omega -dicarboxylates, Aromatic carboxylates have larger binding constants and for o-phthalate the formation of both 1:1 and 1:2 host-guest complexes is observed. Binding of nucleotides (AMP, ADP and ATP) to 1 is surprisingly insensitive to the guest charge, indicating a major contribution of stacking interactions of the nucleobase with 1. Copyright (C) 2001 John Wiley & Sons, Ltd.