Synthesis of an inherently chiral O,O′-bridged thiacalix[4]crowncarboxylic acid and its application to a chiral solvating agent

Treatment of readily available O,O′-1,1,3,3-tetraisopropyldisiloxane-1,3-diyl-bridged p-tert-butylthiacalix[4]arene () with tri(ethylene glycol) di-p-tosylate and subsequent desilylation gave O,O′-bridged thiacalix[4]crown in an excellent yield. Mono-O-alkylation of with ethyl bromoacetate, followed by optical resolution by chiral HPLC, and subsequent hydrolysis of the ester moiety gave inherently chiral O,O′-bridged thiacalix[4]crowncarboxylic acid , which clearly discriminated enantiomeric primary amines, as well as amino esters, by 1H NMR spectroscopy.