Highly selective preparation of conformationally rigid stereoisomeric calix[4]arenes with two carboxymethoxy groups

Highly selective formation of the 1,3-alternate and partial cone conformati onal isomers of p-tert-butylcalix[4]arene diesters 5 with two butoxy and tw o methoxycarbonylmethoxy groups was achieved by alkylations of disubstitute d calix[4]arenes 3 and 4, respectively, with KH as the base in THF The pota ssium diphenoxide form of 3 was shown by NMR-spectroscopy to adopt a 1,3;al ternate conformation which provides strong evidence for a template effect o f potassium cations on the conformation of the calix[4]arene reactant. Alky lation with subsequent hydrolysis of the diesters provides an effective rou te for the preparation of the 1,3-alternate and partial cone isomers of p-t ert-butylcalix[4]arenedicarboxylic acids 6.