Peptide-EBX (5 μmol, 1 equiv.) were weighed on the analytical balance and dissolved in 200 μL non-degassed DMA in a 2 mL vial. Afterwards, 100 μL of a solution of dipeptide ZGP (10 μmol, 2 equiv.) (100 mM in DMA), the peptide solution, 60 μL of a solution of CzIPN (30 mol%, 25 mM in DMA), 25 μL of 2 M K2HPO4 (10 equiv.) in milli-Q purified water and 115 μL of DMA were placed into the vial, overall concentration: 10 Mm. The vial was then capped and degassed by bubbling with N2 for 20 min. The reaction was stirring under Blue LEDs irradiation for 30 min at RT. At the end of the reaction, 10 μL of the crude was diluted with 90 μL of MeCN/water 1:1 and injected in RP-HPLC. The desired products were isolated by Prep-RP-HPLC. HPLC UV ratio was determined by taking the ration of Aprod/Atotal where Aprod = area in mAU of the product peak and Atotal = area in mAU of the combined peptide containing species (product, DMA adduct, iodoalkyne).