A General Synthesis Approach to Double‐Guanidinium Stapled Peptides and Foldamers

In the broader context of peptide macrocyclization, methods enabling the formation of specific crosslinks between orthogonally protected, amino‐functionalized side chains (e.g., Lys–Lys crosslinks) are of potential interest for expanding molecular diversity and stabilizing peptide secondary structures. We recently introduced a solid‐phase synthesis approach for the rapid generation of guanidinium stapled helical peptides and have shown their utility for inhibition of protein–protein interactions. Whereas our previous work concentrated on the formation of mono‐guanidinium crosslinks, we show here that we can expand this approach to prepare bis‐guanidinium stapled peptides and foldamers on‐resin. The methodology similarly uses two orthogonally protected amino‐functionalized side chains and features the use of a diamino connector. The two guanidinium groups are introduced sequentially, the first one intermolecularly and the second intramolecularly. The method is compatible with the i , i + 4 and i , i + 7 cyclization schemes and tolerates a diversity of diamino linkers. We applied the strategy to the synthesis of macrocyclic inhibitors of hDM2 and hDMX and identified several high affinity binders for the two proteins.