Intramolecular chalcogen bonding to tune the molecular conformation of helical building blocks for a supramolecular helix.

We propose to employ intramolecular chalcogen bonding to make a helical building block take its otherwise unfavorable cis -conformation. The 2,5-thiophenediamide motif was taken to bridge two β-turn structures to lead to an azapeptide that exists in cis -conformation and forms a halogen-bonded single-strand helix that exhibits a much stronger supramolecular helicity and a higher thermal stability.