Having proved the synthetic feasibility of late-stage benzodiazole incorporation in intact peptides, we explored the production of CPP derivatives for fluorescence imaging studies. Specifically, we prepared fluorogenic analogues of three reported sequences with different internalization mechanisms (i.e., TAT, penetratin and sC18, Figure ). The three peptides were prepared by SPPS including a C-terminal Cys residue for late-stage labeling and were isolated in yields around 50% and with purities >90% after HPLC purification (see full synthetic and characterization details in Supporting Information). Next, we reacted the three CPPs with the Pd-SNBD complex in 20 mM Tris buffer (pH 7.5) using DMF as cosolvent at 37°C. In all cases, we isolated the SNBD-labeled peptides as the main products (i.e., TAT-SNBD, penetratin-SNBD and sC18-SNBD, Figure ) and with recovery yields around 30%. Notably, we did not observe any cross-reactivity with other polar amino acids (i.e., Arg, Asn, Gln, Glu, Lys, Met) or aromatic amino acids (i.e., Trp and Tyr), and we confirmed the purity and identity of all analogues by HPLC-MS analysis (see full synthetic and characterization details in Supporting Information).