Synthesis and Conformational Property of Tannin-like p-tert-Butylcalix[4]arene 1,3-Diesters Stabilized by Intramolecular Hydrogen Bonds

• Published in: Journal of organic chemistry 2001-11, Vol.66 (24), p.8030-8036
• Main Authors: Nomura, Eisaku, Hosoda, Asao, Taniguchi, Hisaji
• Format: Article
• Language: English
• Subjects: Calixarenes; Crystallography, X-Ray; Esters - chemistry; Gallic Acid - chemistry; Hydrogen Bonding; Hydrolyzable Tannins; Hydroxybenzoates - chemical synthesis; Hydroxybenzoates - chemistry; Macromolecular Substances; Magnetic Resonance Spectroscopy; Molecular Conformation
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo015780o

Tannin-like p-tert-butylcalix[4]arene 1,3-digallate was synthesized, and its conformational property was investigated by dynamic 1H NMR and X-ray crystallography. It was found that the 3-OH (or 5-OH) group of the galloyl group in p-tert-butylcalix[4]arene 1,3-digallate is placed at the position where an unusual nonbonded close contact is observed between the OH group and the aromatic ring of the galloyl group facing each other. The calixarene 1,3-diesters of various hydroxybenzoic acids were also prepared, and the conformational properties of those calixarenes were compared with that of p-tert-butylcalix[4]arene 1,3-digallate. A significant contribution of the 3- and 5-OH groups in pendant groups toward the close contact was found. It was suggested that the conformation of p-tert-butylcalix[4]arene 1,3-digallate was stabilized by intramolecular hydrogen bonds including OH···O and OH−π interactions.