PAT Application in the Expedited Development of a Three-Step, One-Stage Synthesis of the Dipeptide Intermediate of HCV Protease Inhibitor Faldaprevir

A concise scalable synthesis of a chiral dipeptide acid, key substructure of the HCV protease inhibitor faldaprevir, has been developed. A green process with an E-factor of 9.2 was achieved utilizing process analytical technology (PAT) to allow effective processing of multiple-steps in a one-stage operation. Mixed anhydride/oxazolone formation, peptide coupling, saponification, and then crystallization of the desired dipeptide acid were completed within 10 h. MultiMaxIR was used to detect the formation and consumption rates of key intermediates and to provide initial safety data which was subsequently confirmed by more comprehensive process safety testing. Further kinetic analysis was performed to determine the range of operability space to ensure conditions for a robust process