文摘
Proximal di-tert-butylcalix[4]arene (5,11-di-tert-butylcalix[4]arene-25,26,27,28-tetrol) 1b, obtained by direct partial removal of tert-butyl groups from p-tert-butylcalix[4]arene, gave high yields of inherently chiral derivatives upon symmetry breaking by syn-distal di-O-alkylation or di-O-acylation in the presence of K2CO3. The chirality of these compounds was proven by the splitting of 1H NMR signals in the presence of Pirkle's reagent and in some cases by HPLC enantiomeric resolution using chiral stationary phases and corroborated by mirror-image CD spectra.