N-Aminoglycine and Its Derivatives Stabilize PPII Secondary Structure

The identification of unnatural residues that stabilize polyproline type 2 (PPII) folds can aid in the design of peptidomimetics targeting PPII-binding domains. Here, we examine the impact of peptide backbone N-amination on PPII helix stability and find N-aminoglycine (aGly) to be an effective PPII promoter. Further derivatization of an aGly-containing peptide affords N′-alkylated analogues with increased helical propensity. Backbone N-amination of glycine represents a convenient approach to stabilize PPII conformation and allows for the diversity-oriented synthesis of optimally constrained folds.