Betti Chemistry as a Toolkit for Cyclization of Peptides and Generation of Bioactive Macrocycles

Macrocyclic peptides (MPs) are valued molecules in chemical biology due to their high affinity, enhanced stability, and favorable pharmacological properties. However, their broader utility faces limitations. Current cyclization methods often afford restricted structural diversity, which hinders discovery. Here we report a general multicomponent macrocyclization strategy based on the Betti reaction that enables lysine-selective modification and ring closure under mild, peptide-compatible conditions. The reaction tolerates a wide range of aldehydes, carbon nucleophiles, and amino acid contexts, and proceeds efficiently in both solution and on solid support. These features allow the rapid generation of structurally diverse macrocycles with high conversions and substantially improved proteolytic stability. Using this platform, we constructed a 30-member cyclic RGD library and identified several macrocycles with adhesion-blocking activities comparable to or surpassing Cilengitide across two integrin-expressing cell lines. We further demonstrated the modularity of this chemistry by conjugating an optimized RGD macrocycle to the pro-apoptotic peptide KLA, producing a hybrid construct with enhanced cellular uptake, mitochondrial depolarization, and apoptosis induction. Together, these results establish Betti multicomponent macrocyclization as a versatile and powerful method for creating functional macrocycles and modular therapeutic peptide architectures.