Development of a Scalable Enantioselective Synthesis of JAK Inhibitor Upadacitinib

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Process development of a six-stage synthesis of upadacitinib, a JAK1 inhibitor, is described. It is highlighted by an enantioselective and diastereoselective hydrogenation of a tetrasubstituted olefin to set the two pyrrolidine stereocenters. Preparation of the main fragments and strategies to link them together, optimization of the imidazole cyclization, and in-depth understanding of the formation of the urea moiety at the final stage are discussed.