ASYMMETRICALLY SUBSTITUTED CALIXARENES; A TWO-DIMENSIONAL 1H NMR STUDY OF A TETRAESTER DERIVATIVE IN THE CONE-CONFORMATION

Article abstract of DOI:10.1016/S0040-4020(01)96103-4

Several new chiral calix<4>arenes with three or four different substituents in the p-position have been prepared by fragment condensation.Standard derivation procedures always led to the formation of mixtures of various conformational isomeres from which the derivative in the cone-conformation could be isolated only by preparative HPLC.For a tetraester derivative it was shown by two-dimensional 1H NMR spectroscopy, that due to the different substituents the cone-conformation is strongly distorted.The sodium complex of this tetraester, however, assumes a regular cone-conformation again.