Peptide-based natural products have long served as inspiration in the development of new therapeutics for the treatment of human disease. Therapeutic peptides commonly exhibit effective protein-target binding activity at low concentrations as a result of high selectivity. However, the value of peptide therapeutics is often overshadowed by a marked susceptibility to proteolytic degradation and subsequent failure to reach a validated target in vivo. The modification of bioactive linear peptides by macrocyclization has shown to be a promising strategy for addressing this problem. Drawing inspiration from Nature’s wide collection of non-ribosomal peptides, specifically those comprising electron-rich aromatic moieties, we aim to augment current methodology by developing new chemical strategies for the synthesis of cyclic and stabilized peptides by leveraging the inherent nucleophilicity of Tyr and Trp residues. Due to their remarkable reactivity toward various aromatic nuclei such as phenols (Tyr) and indoles (Trp), we have identified N-4-substituted azo reagents, namely, 1,2,4-triazoline-3,5-diones (TADs), as chemoselective electrophiles for the construction of macrocyclic peptidomimetic scaffolds. Upon synthesizing an N4-substituted 1,2,4-triazolidine-3,5-dione (aka urazole) at the N-terminus of a solid-supported peptide, the urazole moiety is chemoselectively oxidized under mild conditions to generate a TAD derivative in situ. The subsequent reaction of this electrophilic TAD moiety with the sidechain aromatic nuclei of internally or terminally located Tyr or Trp residues should result in the chemoselective formation of peptidic macrocycles. This poster will give an overview of recent progress concerning the development of this method, as well as the successful synthesis of macrocyclic peptides wherein the TAD moiety has been trapped by the phenolic sidechain of Tyr. Results regarding LC-MS, 1-D NMR, and 2-D NMR experiments will be discussed. Furthermore, preliminary evidence which supports the trapping of the electrophilic TAD by the sidechain of Trp will be presented.