| Abstract
| - Tannin-like p-tert-butylcalix[4]arene 1,3-digallate was synthesized, and its conformational propertywas investigated by dynamic 1H NMR and X-ray crystallography. It was found that the 3-OH (or5-OH) group of the galloyl group in p-tert-butylcalix[4]arene 1,3-digallate is placed at the positionwhere an unusual nonbonded close contact is observed between the OH group and the aromaticring of the galloyl group facing each other. The calixarene 1,3-diesters of various hydroxybenzoicacids were also prepared, and the conformational properties of those calixarenes were comparedwith that of p-tert-butylcalix[4]arene 1,3-digallate. A significant contribution of the 3- and 5-OHgroups in pendant groups toward the close contact was found. It was suggested that the conformationof p-tert-butylcalix[4]arene 1,3-digallate was stabilized by intramolecular hydrogen bonds includingOH···O and OH−π interactions.
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