Synthesis and ion selectivity of all conformational isomers of tetrakis[(ethoxycarbonyl)methoxy]calix[4]arene

TLDR: In this paper, the conformer distribution in tetra-O-alkylation of 5,11,17,23,tetra-tert-butylcalix[4]arene-25,26,27,28-tetrol by ethyl bromoacetate is remarkably affected by the metal cation present in the base.

Abstract: We have found that the conformer distribution in tetra-O-alkylation of 5,11,17,23-tetra-tert-butylcalix[4]arene-25,26,27,28-tetrol by ethyl bromoacetate is remarkably affected by the metal cation present in the base. In general, the cone conformer predominantly results when the base contains template metal cations whereas the partial-cone and 1,3-alternate conformers result when the base contains nontemplate metal cations; in acetone solvent one can realize the change from the 100% cone selectivity to the 100% partial-cone selectivity. By combining the metal template effect with a protection-deprotection method with a benzyl group, we developed synthetic routes to all of the four conformers. Two-phase solvent extraction established that the cone conformer shows Na + selectivity whereas the remaininig three conformers show K + selectivity