We report a full account of our work toward the totalsynthesis of pseudolaric acid B (1a), a diterpene acid isolated from the bark of Pseudolarix kaempferi Gordon (pinaceae). Compound 1a is an antifungal and antifertility agent. Furthermore, its capacity for inhibitingtubulin polymerization makes it a potential lead for cancer therapy. Herein, we describe the use of a Ru- or Rh-catalyzed [5 + 2]