Aiming at precisely arranging several proteinogenic α-amino acids on a folded scaffold, we have developed a cyclic hexapeptide comprising an alternate sequence of biphenyl-cored ζ-amino acids and proteinogenic α-amino acids such as l-leucine. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form a target cyclic peptide. Theoretical analyses and NMR spectroscopy suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible in CHCl . The optical properties including UV/Vis absorption, fluorescence, and circular dichroism (CD) were also evaluated. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups at the periphery of the cyclic skeleton. This α/ζ-alternating cyclic peptide is therefore expected to serve as a unique scaffold for arranging several functionalities.

A water‐soluble cyclic hexapeptide comprising an alternate sequence of biphenyl‐cored ζ‐amino acids and proteinogenic α‐amino acids such as l‐leucine has been developed. The amino acids were connected by typical peptide synthesis, and the resultant linear hexapeptide was intramolecularly cyclized to form the target cyclic peptide. Theoretical and NMR spectroscopic analyses suggested that the cyclic peptide was folded into an unsymmetrical conformation, and the structure was likely to be flexible. Furthermore, the cyclic peptide became soluble in water by introducing three carboxylate groups. More information can be found in the Full Paper by Mitsuhiko Shionoya et al. on page 1087 in Issue 10, 2017 (DOI: 10.1002/asia.201700203).