Peptide Late-Stage Diversifications by Rhodium-Catalyzed Tryptophan C7 Amidation

Abstract

Summary The late-stage diversification (LSD) of structurally complex peptides has emerged as a powerful platform for molecular engineering and drug discovery. Besides traditional peptide modifications, such as native chemical ligations or cross-couplings with prefunctionalized substrates, during recent years, C―H activation has gained considerable momentum as a robust and step-economical strategy for late-stage peptide modifications, thus far predominantly for the formation of C―C bonds. Although C―N bond formations represent established strategies in medicinal chemistry and drug discovery, methods for direct amidations of tryptophan and tryptophan-containing peptides are rare and severely limited to the activated C2 position. In contrast, we herein disclose the first example of direct late-stage peptide C―H amidation reaction and the unprecedented late-stage peptide diversification on tryptophan C7 position in a highly site-selective manner. Moreover, this strategy sets the stage for sequential double C(7)―H/C(2)―H modifications, further improving the peptide structural complexity.