Synthesis, NMR conformational analysis, complexation and transport studies of an inherently chiral dihomooxacalix[4]arene triester

The synthesis of the inherently chiral triethyl ester monomethyl ether of p-tert-butyldihomooxacalix[4]arene (3) is reported. A distorted cone conformation in solution at room temperature has been established for triester 3 by NMR measurements (1H, 13C, NOE 1D and 2D). The extracting and complexing properties of 3 towards the entire alkali and alkaline earth cation series have been assessed by picrate extraction and stability constant determinations. Transport experiments with metal picrates through a CH2Cl2 membrane have also been performed. Comparison is made with tetraethyl ester of p-tert-butylcalix[4]arene (4) described in literature and also studied by us. 3 is a poor phase transfer agent and binder. In contrast, it is a good carrier, mainly for the alkali cations and displays a selective transport for Ba2+.