Cyclophilin inhibition has been a target for the treatment of hepatitis C and other diseases, but the generation of potent, drug-like molecules through chemical synthesis has been challenging. In this study, a set of macrocyclic cyclophilin inhibitors was synthesized based on the core structure of the natural product sanglifehrin A. Initial compound optimization identified the valine-m-tyrosine-piperazic acid tripeptide (Val-m-Tyr-Pip) in the sanglifehrin core, stereocenters at C14 and C15, and the hydroxyl group of the m-tyrosine (m-Tyr) residue as key contributors to compound potency. Replacing the C18-C21 diene unit of sanglifehrin with a styryl group led to potent compounds that displayed a novel binding mode in which the styrene moiety engaged in a π-stacking interaction with Arg55 of cyclophilin A (Cyp A), and the m-Tyr residue was displaced into solvent. This observation allowed further simplifications of the scaffold to generate new lead compounds in the search for orally bioavailable cyclophilin inhibitors.
Cyclophilins/antagonists & inhibitors , Cells, Cultured , Chromatography, Liquid , Crystallography, X-Ray , Drug Discovery , Humans , Hydrogen Bonding , Lactones/chemistry , Lactones/pharmacology , Proton Magnetic Resonance Spectroscopy , Spectrometry, Mass, Electrospray Ionization , Spiro Compounds/chemistry , Spiro Compounds/pharmacology , Structure-Activity Relationship , Surface Plasmon Resonance , Thermodynamics
