Chemoenzymatic Synthesis, Mode of Action and Evolution of Natural Product-based Macrocycles Natural peptide macrocycles are promising next-generation therapeutics, due to their abilities to bind to challenging protein targets, such as protein interfaces and transcription factors. The goal of our lab is to use insights and chemistries from natural product biosynthesis to facilitate the discovery and development of new natural product-like peptide macrocycles. We will use a combined chemical and enzymatic approach for synthesis of highly constrained peptide macrocycles similar to those used in nature. Over the next five years, these efforts will be divided amongst three project areas. In the first project, we develop a chemoenzymatic platform for the preparation of analogs of the thiopeptide natural products. We further exploit this platform to examine new, diversity generating enzymes from complimentary ribosomal natural product pathways. In the second project, we will investigate the multi-faceted biological activities of thiopeptides and develop potent and selective inhibitors of the oncogenic transcription factor FoxM1. A major thrust of this research will be structure elucidation of thiopeptides bound to FoxM1. In the final project, we combine enzymes from ribosomal peptide natural product with mRNA display to allow laboratory scale directed evolution of new peptide macrocycle inhibitors. This work is expected to yield new avenues and technologies for development of peptide macrocycle-based therapeutics.