“…We therefore explored whether Azp-containing oligoprolines can be functionalized, for example, by Huisgen's 1,3-dipolar cycloadditions ('click chemistry') [10] and prepared the 18-mer Ac-[Pro-(4R)Azp-Pro] 6 -OH (4) with Azp residues in every third position. [9] Within peptide 4 all azido groups were designed to be positioned on one edge of the PPII helix in aqueous solution as supported by CD and NMR spectroscopy. Under typical click chemistry conditions, the six azido groups within 4 reacted readily with, for example, methyl propiolate to the desired hexatriazole 5 (Scheme 1).…”