Assessing stabilization through π-π interactions in aromatic oligoamide β-sheet foldamers

We have recently introduced aromatic oligoamide β-sheet foldamers based on rigid turn units and short linear strands that undergo intramolecular π-π stacking (Sebaoun, L.; Maurizot, V.; Granier, T.; Kauffmann, B.; Huc, I. J. Am. Chem. Soc. 2014, 136, 2168). We now report that conformational stability in these structures can be reached using less rigid turn units and more extensive π-π interactions between longer linear strands. For this study, two-stranded sheets of variable length were prepared. Their conformation was assessed in solution by (1)H NMR and in the solid state by X-ray crystallography.