Induced helix of 2-(2-aminophenoxy)alkanoic acid oligomers as a δ-peptidomimetic foldamer

Peptidomimetic foldamers were synthesized by oligomerizing derivatives of the δ-amino acid analogue, 2-(2-aminophenoxy)alkanoic acid. Single-crystal analysis of the tetramer reveals a 21-helical secondary structure stabilized by hydrogen bonding and the coiled stacking of aromatic rings. The M-helicity of 2-aminophenoxyacetic acid oligomers was induced by the incorporation of only a single chiral carbon of the N-terminal (R)-2-(2-nitrophenoxy)propionamide moiety. The solution state CD spectra demonstrated that the resulting helix induced a substantial Cotton effect. The secondary structure was further characterized by IR and NMR spectroscopy.