Conformational studies on model peptides with 1-aminocyclopropane 1-carboxylic acid residues

The design of metabolically stable, conformationally constrained peptidomimetics is an increasingly used approach in developing orally active drug candidates in pharmaceutical research. In this paper we present conformational energy calculations on model compounds containing 1-aminocyclopropane carboxylic acid (ACC) and its derivatives using molecular mechanics methods. The low energy models adopt conformations characteristic of a variety of regular structures such as the alpha-helix, gamma-turn and three- and fourfold helices. The energetically most favored models adopt either the left- or right-handed 2.2(7) helical conformation or the gamma-turn. These results are qualitatively consistent with the crystal structures of peptide analogs containing ACC and have potential implications for the design of peptidomimetics where the conformational features characteristic of a specific type of gamma-turn are desired.