Hydrogen-bonding-induced oligoanthranilamide foldamers. Synthesis, characterization, and complexation for aliphatic ammonium ions

• DOI: 10.1016/j.tet.2005.06.042
• Publication Date: 2005-07-02T14:48:06Z
• Authors: Hui-Ping Yi; Chuang Li; Jun-Li Hou; Xi-Kui Jiang; Zhan-Ting Li
• Keywords: Amide; Proton NMR; Foldamer

Abstract The self-assembly of a novel series of intramolecular hydrogen bonding-driven foldamers have been described. Five linear aromatic amide oligomers 1–5 , which bear two to six repeating benzoyl amide subunits, respectively, have been prepared by continuous amide-coupling reactions. The existence of three-centered hydrogen bonds in the oligomers and consequently, the folding conformation of the oligomers in the solid state and solution have been proved by the X-ray analysis (for 2 ) and the 1H NMR and IR experiments. Molecular modeling reveals a planar and rigid conformation for the oligomers and a cavity of 0.86 nm in diameter for 6-mer 5 . Fluorescent and 1H NMR experiments have demonstrated that the new aromatic oligo-amide foldamers can bind primary and secondary alkyl ammonium ions in chloroform and the associated binding constants have been determined. It is revealed that 5-mer 4 exhibits the largest binding ability. A face-to-face binding mode has been proposed for the complexes.