Development of the Convergent, Kilogram-Scale Synthesis of an Antibacterial Clinical Candidate Using Enantioselective Hydrogenation

Early chemical development studies into the best way of assembling AZD9742, an antibacterial drug candidate, have involved swapping the order of two reductive aminations. The orthogonally functionalized aminopiperidine partner for these couplings is now enantioselectively synthesized using ruthenium-catalyzed asymmetric hydrogenation. The challenge of controlling defluorination through an appropriate catalyst choice has hitherto prevented this revised sequence from reaching its full potential. However, it is still shown to allow access to the active pharmaceutical ingredient in a stereochemically pure form and has been demonstrated on a multikilogram scale. The reductive aminations in both the original and revised sequences provided different scale-up challenges, and the solutions implemented are described.