Synthesis, structure and anion binding properties of lower rim α-hydroxyamide calix[4]arene derivatives

A new family of p-tert-butylcalix[4]arenes functionalized at the lower rim with alpha-ketoamide or alpha-hydroxyamide functions has been prepared. The H-1 and (CMR)-C-13 spectra indicate that the macrocycles preferably adopt a cone conformation. X-ray crystal study of the a-ketoamide derivative 4a shows the flattened cone conformation in the solid state. Reduction of alpha-ketoamide 4ab has produced the alpha-hydroxyamide derivatives 6ab. The introduction of chiral moieties on the lower rim position of the calix[4]arene allowed the synthesis of the chiral derivatives 7 and 8. Host-guest complexation properties towards various anions of the chiral a-hydroxyamide 8 have been examined by H-1 NMR spectroscopy. This new receptor has shown promising selectivity for H2PO4- and N-tosyl-(L)-alanmate. (c) 2005 Elsevier Ltd. All rights reserved.