Synthesis and characterization of retro gramicidin A‐dAla‐gramicidin A, a 31‐residue‐long gramicidin analogue

A 31-residue peptide, retro gramicidin A-dAla-gramicidin A, mimicking a gramicidin A dimer was prepared by solid phase method using a 4-(oxymethyl)-Pam resin and BOC as α amino protecting group. To avoid any possible formation of gramicidin A, couplings of fragments were used together with stepwise growing of the peptide chain. After purification by silica gel chromatography, this peptide was shown to form long living channels in lipid bilayer. Preliminary physicochemical investigations suggest that the peptide does not adopt the expected π6.3DL helical conformation.