Design, Synthesis and Structural Investigations of a β‐Peptide Forming a 3 14 ‐Helix Stabilized by Electrostatic Interactions

Two different strategies have been employed for the synthesis of Fmoc‐protected β 3 ‐homoarginine; the Arndt–Eistert homologation of α‐arginine and the guanidinylation of β 3 ‐homoornithine. Solid‐phase β‐peptide synthesis was used for the preparation of β‐heptapeptide 1 , which was designed to form a helix stabilized by electrostatic interactions through positively (β 3 hArg) and negatively charged (β 3 hGlu) amino acid residues. CD measurements and corresponding NMR investigations in MeOH and aqueous solutions do indeed show that the β‐peptidic 3 14 ‐helix can be stabilized by salt‐bridge formation.