Synthesis of linear and cyclic aromatic peptides with fixed conformation owing to intramolecular hydrogen bonding by condensation polymerization method

Chain-growth condensation polymerization of 3-(4-octyloxybenzylamino)benzoic acid esters bearing an alkoxy group on the benzene ring was investigated for the synthesis of polyamides having a specific conformation owing to intramolecular hydrogen bonding of CONH⋯OR. The 4-octyloxybenzyl group on the nitrogen of the amide linkage was easily removed with trifluoroacetic acid after polymerization to afford the desired polyamides, which had lower solubility than expected. Furthermore, we found that a cyclic triamide was selectively obtained by slow addition of the base to a solution of the monomer.