The synthesis and conformational studies of chiral calix[6]arene derivatives bearing amino acid ester residues

Chiral calix[6]arene derivatives were synthesized by the reactions of N-chl oroacetyl amino acid ester and 1,3,5-trimethoxy-p-tert-butylcalix[6]arene i n the presence of K2CO3. The self-inclusion of the anisole methoxy groups i nto the calix-cavity stabilizes the compounds in the major flattened cone. conformer as shown by their H-1 NMR spectra. The larger substituents on the 2,4,6-positions have larger contributions to the stabilities of the compou nds. The theoretical calculations by Molecular Force Field Method furthermo re indicate that they are prone to exist in a flattened cone conformation. (C) 2000 Elsevier Science Ltd. All rights reserved.