Process Development of a Suzuki Reaction Used in the Manufacture of Lanabecestat

We developed a scalable Suzuki process for the synthesis of lanabecestat (+)-camsylate, an active pharmaceutical ingredient that was recently investigated in a Phase III clinical program for the treatment of early Alzheimer’s disease. The evolution of this process culminated with the use of a stable and crystalline diethanolamine boronic ester that rapidly hydrolyses under the reaction conditions. Herein, we report that the liberated diethanolamine plays an important role in the catalytic process, with supporting evidence for an equilibrium between an unbound and bound palladium complex. Additionally, the diethanolamine acts as an internal scavenger during the crystallization of lanabecestat by increasing the solubility of the palladium species, obviating the need for a discrete scavenging step.