Final Report Summary - CYSTEINE-FREE NCL (Development of a new methodology for the synthesis of mercapto amino acids for protein synthesis by cysteine-free native chemical ligation.) To improve the understanding of disease states, scientists need to investigate the cellular pathways involved in their development. Stapled peptides not only represent a valuable tool to study protein-protein interactions and to identify new drug targets, they also potentially make powerful therapeutics. Despite the importance of stapled peptides in nowadays drug discovery programs, very few methods currently feature in the chemists's toolbox to prepare these precious entities. Simultaneously C-H activation has emerged as a practical method to readily functionalised natural products and pharmaceuticals. This project aimed at the development of a new stapling technology using state-of-the-art C-H activation chemistry. During the course of this project an efficient protocol for the stapling of peptides was developed in-solution. The scope of the reaction was evaluated. A library of 25 stapled peptides was prepared using the optimized reaction conditions identified, thus demonstrating the compatibility of the reaction with a broad range of substrates. Parameters such as the size and the length of the staple were also evaluated. Next, a more practical on-resin protocol was established which should allow chemists to readily access these novel entities. Finally, the stability of these novel cross-linked peptides to protease degradation was evaluated as well as their propensity to generate specific secondary structures. These new stapled peptides were found to dramatically increase the half-life of the molecules, thus addressing one of the major drawbacks of standard peptides. In conclusion, the new technology developed is expected have a tremendous impact on drug discovery, by providing an efficient method to readily access novel stapled peptide entities, useful for the understanding of the biological processes involved in the development of diseases and for the design of novel powerful drugs.
