Cyclic trimer of 5-(aminomethyl)-2-furancarboxylic acid as a novel synthetic receptor for carboxylate recognition

A novel 18-membered cyclic oligopeptide 1 based on 5-(aminomethyl)-2-furancarboxylic acid (2), is developed as an excellent receptor for carboxylate binding having an association constant of 8.64×103 M−1 for tetrabutylammonium acetate in CD3CN. The synthesis of 1 was achieved by a high-yielding cyclotrimerization reaction of the unfunctionalized furan amino acid 2.