Ligations of N-acyl tryptophan units to give native peptides via 7-, 10-, 11-and 12-membered cyclic transition states

N-Acyl tryptophan isopeptides undergo acyl transfer in chemical ligations via 7-, 10-, 11- and 12-membered cyclic transition states to yield natural peptides, representing the first examples of successful isopeptide ligations from N-acyl tryptophan units.