Foldamers of bifunctional diketopiperazines displaying a β-bend ribbon structure

The synthesis of two oligomers, of a bifunctional diketopiperazine scaffold DKP-1, formally derived from the cyclization of L-aspartic acid and (S)-2,3-diaminopropionic acid, is reported. A trimeric and a tetrameric structure were prepared by solution-phase peptide synthesis (Boc strategy). Conformational analysis of these derivatives was carried out by a combination of H-1 NMR spectroscopy, CD spectroscopy, and molecular modeling, and revealed the formation of beta-bend ribbon involving 10-membered H-bonded rings and a reverse turn of the growing peptide chain. (C) 2010 Elsevier Ltd. All rights reserved.