Synthetic studies on pseudolaric acid B: Construction of the trans-fused [5–7] ring system via Dieckmann condensation

Pseudolaric acids A (1) and B (2) are diterpene acids isolated from the root bark of Pseudolarix kaempferi as the main biologically active constituents of tujinpi, a traditional Chinese medicinal herb. Studies toward the total synthesis of 2 are described. The unusual trans-fused [5–7] ring system in the core structure of 2 was successfully synthesized via Dieckmann condensation.