Oligoindole-based foldamers with a helical conformation induced by chloride.
As a new type of foldamers, oligoindoles containing 4, 6, and 8 indole rings were synthesized, and their folding properties were characterized by a combination of 1H NMR techniques and UV/visible titration experiments. When chloride was added, the NH signals of the oligoindoles were downfield shifted as a result of hydrogen-bond formation, and the aromatic signals were upfield shifted by stacking between two indoles. Moreover, the ROESY experiment provided definitive NOE evidence for the helical stacking in the presence of chloride. Finally, the UV/visible titration experiments demonstrated that the oligoindoles formed 1:1 complexes with chloride, and the association constants greatly increased with increasing the number of the indole NHs. These observations are all consistent with the fact that oligoindoles adopt a helical conformation when complexed with chloride by hydrogen-bonding interactions.
Chang
Kyoung-Jin
KJ
Center for Bioactive Molecular Hybrids and Department of Chemistry, Yonsei University, Seoul 120-749, South Korea.
Kang
Byung-Nam
BN
Lee
Min-Hee
MH
Jeong
Kyu-Sung
KS