Strategy for the Synthesis of the [7–5–7–6] Tetracyclic Core of Daphnipaxinin

Herein, we report an efficient approach for the direct synthesis of the [7-5-7-6] tetracyclic framework of daphnipaxinin, which contains two synthetically challenging medium-sized rings. The acid-promoted type I [5 + 2] cycloaddition reaction was used as the key step, which directly constructed a synthetically challenging [7-7] fused A/D ring system and the desired all-carbon quaternary stereocenter diastereoselectively.