Remarkable alkali cation template effect in 1,5-bridged calix[8]arenes

Org Lett. 2001 May 31;3(11):1605-8. doi: 10.1021/ol015766y.

Abstract

Treatment of 1,5-bridged calix[8]arenes 2-4 with alkali metal carbonates produces salts in which an included cation acts as a conformational template. This induces the folding of calix[8]arene skeleton in a conformation in which the triads of contiguous OH-bearing rings adopt a 3/4-cone conformation with all hydroxyls converging toward the same center. The template effect requires the presence of short bridges (ethylene, tetramethylene, diethylene glycol) and became stronger by increasing the cation dimension up to that of Cs(+).