Development of an Efficient New Route to PPARδ Agonist Fonadelpar: Formation of the C–C Bond by Claisen Condensation

An efficient new synthesis of a peroxisome proliferator-activated receptor delta agonist fonadelpar was developed. The new process features a more practical approach to construct the ethylene linker of fonadelpar by coupling an advanced aldehyde and a ketone via Claisen–Schmidt condensation, which is followed by hydrogenation and an optimized process to obtain the isoxazole moiety. The convergent synthesis provides a robust and scalable approach to prepare the drug candidate in significantly fewer steps and with a higher yield.