Local versus Global Control of Helical Folding in β-Peptide Segments Using Hydrazino Turns.

Rational control of the self-organization of β-peptides sequences to adopt regular secondary structures is an important challenge in peptidomimetic foldamer science. By replacing the N- and C-terminal residues of homooligomers of trans-2-aminocyclobutanecarboxylic acid (tACBC)n with N-aminoazetidine-2-carboxylic acid, an 8-helical topology is shown to dominate for sequences up to n = 7. This constitutes an atomic-level tool to override locally the preferred global 12-helix secondary structure of the corresponding tACBC homooligomers of the same length.