Helical templating of oligopeptides by cyclodextrin dimers Original Research Article

β-cyclodextrin-based receptors were synthesized and tested for their ability to induce a helical fold in peptides bearing hydrophobic amino acid residues in the i, i+11- or i, i+14-positions. Circular dichroism experiments revealed that a dimeric β-cylodextrin receptor synthesized from a [1,1′-biphenyl]-4,4′-dithiol core demonstrated an ability to fold a designed peptide bearing the artificial amino acid l-p-t-butylphenylalanine in the i, i+11-positions, while other dimeric and monomeric receptors failed to do so. Titration studies were performed using both circular dichroism and calorimetry, the analysis of which yielded an apparent Ka on the order of 104–105 M−1. However, no evidence could be obtained for helical folding with a peptide carrying tryptophan residues in place of the p-t-butylphenylalanine units. Our studies suggest that receptors of this type may be useful in molecular recognition of hydrophobic, already α-helical peptides in aqueous solution.