Metallo-azapeptides: Controlled Metal Chelation to Peptide Backbone Nitrogen.

We present the first approach to controlled metal chelation of peptide backbones, where the anchoring site is an aza-amino acid nitrogen and the directionality of chelation events is dictated by the acidity of neighboring NHs. Selective backbone chelation precludes the need for metal-binding side chains and/or free - or -termini in peptides. We show that the presence and location of an aza-amino acid impact complex formation and report the first X-ray crystal structures of azapeptides bound to palladium and nickel. Evidence of atropisomerism in metallo-azapeptides is also presented.