Automated High-purity On-resin Cyclization Strategy for Rapid Synthesis of Homodetic Cyclopeptides

Ribosomes rapidly produce cyclopeptides in minutes but are restricted to natural amino acids. Now, an automated chemical method using the iChemAFS synthesizer matches ribosomal speed while incorporating both natural and non-natural amino acids. A specifically designed diaminonicotinic acid (DAN) linker precisely controls chain elongation and cyclization, allowing for one-step, cleavage-free synthesis of cyclopeptides with up to 95% crude purity. The platform supports 6- to 39-membered rings and scales from milligrams to grams. In just one day, a 20-member cyclopeptide library was synthesized, yielding a screened sequence with 100-fold greater antimicrobial activity against S. aureus and B. subtilis than penicillin. This method offers a fast, flexible alternative to ribosomal synthesis, supporting the development of personalized therapeutics.