A General Strategy to Install Amidine Functional Groups Along the Peptide Backbone.

Amidines are a structural surrogate for peptide bonds, yet have received considerably little attention in peptides due to limitations in existing methods to access them. The synthetic strategy developed in this study represents the first robust and general procedure for the introduction of amidines into the peptide backbone. We exploit and further develop the utility and efficiency of thioimidate protecting groups as a means to side-step reactivity that ultimately renders existing methods unsuitable for the installation of amidines along the main-chain of peptides. This work is significant because it describes a generally applicable path to access unexplored peptide designs and architectures for new therapeutics made possible by the unique properties of amidines.