Practical synthesis of a vanilloid receptor-1 antagonist.

Small molecule TRPV1 antagonists have been a recent focus in the search for pain treatment agents. We herein describe a practical and scalable synthesis of AMG 628 (1), a bis-substituted pyrimidine derivative that was identified as a highly efficacious agent, suitable for clinical development. Highlights of our approach include a practical route to a substituted benzothiazole, a scalable synthesis of an enantiopure piperazine fragment, and identification of conditions for selective coupling reactions on 2,6-dichloropyrimidine, to access the active pharmaceutical ingredient in high purity and overall yield.