Development of a Factory Process for Omecamtiv Mecarbil, a Novel Cardiac Myosin Activator

The development of a factory process to manufacture the novel cardiac myosin activator omecamtiv mecarbil (1) is described. Omecamtiv mecarbil is prepared via the convergent synthesis and coupling of two key fragments, aniline 2 and carbamate 4-HCl, which serves as a masked isocyanate. To enable practical access to aniline 2, reduction of the corresponding nitroaromatic was designed to control potential mutagenic impurities. Key to the efficient preparation of 2 was the benzylic bromination of 8 followed by selective debromination of a gem-dibromide byproduct and subsequent alkylation with 5-phosphate. Overall, the longest linear sequence consists of six steps, including a final salt formation step to afford the drug substance in 55% overall yield. Because of poor performance of the original free-base form of the drug substance in modified-release formulations, an improved dihydrochloride hydrate form was developed to aid drug product performance and manufacturability.