Many strategies exist to install macrocyclic rings within peptides before or after biological display. Common methods include disulfide formation between Cys side chains, thioether formation between a Cys side chain and a terminal chloroacetamide or benzyl halide, copper-catalyzed azide-alkyne cycloaddition, amide bond-forming reactions , and a variety of metal-catalyzed macrocyclizations . Although widely employed, each of these methods suffers from at least one liability with respect to downstream applications and none provide added value: Disulfide bonds are reversible, while thioethers are flexible and, like click reaction products, prone to oxidation. Alternative macrocyclization strategies that generate stable and drug-like linkers are widely recognized as an unmet need . Chemistry that exploits the macrocyclization event to establish a known pharmacophore within the peptide backbone prior to biological display is a promising strategy towards this end .