Design, Synthesis and Structural Investigations of a β-Peptide Forming a 3<INF>14</INF>-Helix Stabilized by Electrostatic Interactions

Two different strategies have been employed for the synthesis of Fmoc-protected β³-homoarginine; the Arndt–Eistert homologation of α-arginine and the guanidinylation of β³-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 (β³hArg) and negatively charged (β³hGlu) amino acid residues. CD measurements and corresponding NMR investigations in MeOH and aqueous solutions do indeed show that the β-peptidic 3<INF>14</INF>-helix can be stabilized by salt-bridge formation.