A scalable and robust process was developed for the preparation of pexacerfont (2), a pyrazolotriazine corticotropin-releasing factor receptor 1 antagonist (CRF1). The formation of the core hydroxypyrazolotriazine moiety was achieved through two consecutive cyclizations of a semicarbazide, employing reaction conditions that are significantly milder than those reported in the literature. Further conversion to the key chloropyrazolotriazine intermediate was accomplished through a novel catalytic process using phosphorous oxychloride as the chlorinating agent. The active pharmaceutical ingredient 2 was obtained in >99.5% purity with a 68% overall yield for the six synthetic steps.
This manuscript describes the control strategy for the commercial process to manufacture brivanib alaninate. The active pharmaceutical ingredient is a prodrug which is susceptible to hydrolysis. In addition to controlling hydrolysis, a robust strategy was required in order to control input and process-related impurities. Three significant aspects of control include understanding of the reaction parameters in order to minimize the regioisomer during the alkylation with (R)-propylene oxide, development of a design space through statistical models to control impurity formation, and the use of in situ FT-IR to monitor the hydrogenolysis of the Cbz protecting group.
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