Olefin ring-closing metathesis as a powerful tool in drug discovery and development – potent macrocyclic inhibitors of the hepatitis C virus NS3 protease

Peptidomimetic inhibitors of the hepatitis C NS3 protease often exhibit poor biopharmaceutical properties. Structure modification of a substrate-based tripeptide into a β-strand 15-membered ring scaffold provided a new class of peptidomimetics that are significantly superior as drug candidates to their acyclic precursors. Tripeptide dienes composed of three unnatural amino acid residues with numerous chiral centers were efficiently converted to macrocyclic peptides, in high diastereomeric purity, using ring-closing metathesis (RCM). The conformation of the acyclic diene and the protocol for the RCM reaction were investigated and optimized extensively in order to achieve an efficient synthesis of potential therapeutic agents for the treatment of hepatitis C infections. These studies provided the fist small molecule (BILN 2061) that was clinically validated for the treatment of hepatitis C infection in man and opened the door to a plethora of new pre-clinical pharmaceutical agents that can be made in multi kilogram quantities using RCM chemistry.