Asymmetric Synthesis of the Cyclohexyl Fragment in RORγt Inhibitor (BMS-986251) Enabled by a Dynamic Kinetic Resolution of Hageman’s Ester

The cyclohexyl fragment 1 in BMS-986251 was synthesized starting from Hagemann's ester 2 in 7 steps and 5 isolations. The route is highlighted by a dynamic kinetic resolution (DKR), a telescoped enol nonaflation followed by a palladium-catalyzed carbonylation, and a rhodium-catalyzed directed diastereoselective olefin hydrogenation. The optimized process was demonstrated on 1 kg scale, with an overall 51% yield and >99% ee and dr.