Peptide Macrocyclization Assisted by Traceless Turn Inducers Derived from Ugi Peptide Ligation with Cleavable and Resin-Linked Amines

A multicomponent approach enabling the installation of turn-inducing moieties that facilitate the macrocyclization of short and medium-size oligopeptides is described. The strategy comprises the Ugi ligation of peptide carboxylic acids and isocyanopeptides in the presence of aldehydes and acid or photolabile amines followed by cyclization and cleavage of the backbone N-substituents to render canonical cyclopeptides. Implementing the approach on solid phase with the use of Rink amide resins led to a new class of backbone amide linker strategy.