To confirm the structural identity of the linkage in 16, selected examples, 16d and 16e, were characterized by 1 H, C, and 2-D nuclear magnetic resonance (NMR) spectroscopy experiments. In general, the comparative analysis of 1 H NMR spectra for acyclic (14) vs. cyclic (16) peptides rapidly reveals the structural change that occurs upon cyclization. This is demonstrated in a comparison of 1 H NMR spectra of 14i and 16i, wherein a diagnostic ABX signal is observed at 7.14 ppm (dd, J = 8.5, 2.2 Hz) in 16i indicating the asymmetry of the trisubstituted Tyr residue (Figure ). Moreover, analysis of 16c and 16d by gHMBCAD and gHMQC 2-D NMR experiments support the Tyr-linked connectivity in cyclic peptides (16) (see the Supplementary Information).