The First Asymmetric Pilot-Scale Synthesis of TV-45070

TV-45070 is a small-molecule lactam containing a chiral spiro-ether that has been reported as a potential topical therapy for pain associated with the Nav1.7 sodium ion channel encoded by the gene SCN9A. A pilot-scale synthesis is presented that is highlighted by an asymmetric aldol coupling at ambient temperature, used to create a quaternary chiral center. Although only a moderate ee is obtained, the removal of the undesired isomer is achieved through preferential precipitation of a near racemic mixture from the reaction, leaving the enantiopure isomer in solution. Cyclization to form the final API uses an uncommon diphenylphosphine-based leaving group which proved successful on the neopentyl system when other traditional leaving groups failed.