Construction of supramolecular helices and breaking the helicity by forming supramolecular β-sheet structures using suitable self-assembling pseudopeptide building blocks

Abstract

Bis-valine derivatives of malonamide (Guha, S.; Drew, M. G. B. Small 2008, 4, 1993−2005) and a bis-valine derivative of 1,1-cyclopropane dicarboxamide were used as building blocks for the construction of supramolecular helical structures. The six-membered intramolecular hydrogen-bonded scaffold is formed, and this acts as a unique supramolecular synthon for the construction of a pseudopeptide-based supramolecular helical structure. However, in absence of this intramolecular hydrogen bond, intermolecular hydrogen bonds are formed among the peptide strands. This leads to a supramolecular β-sheet structure. Proper selection of the supramolecular synthon (six-membered intramolecular hydrogen-bonded scaffold) promotes supramolecular helix formation, and a deviation from this molecular structure dictates the disruption of supramolecular helicity. In this study, six crystal structures have been used to demonstrate that a change in the central angle and/or the central core structure of dicarboxamides can be used to design either a supramolecular helix or a β-sheet.