Synthetic Studies toward the Berkeleyacetal Core Architecture.

Berkeleyacetals are structurally complex natural products that have shown potent anti-inflammatory activity. The presence of a highly dense oxygen functionality and a polycyclic ring system presents significant synthetic challenges. Herein, we report an efficient strategy for the construction of the tetracyclic core system of berkeleyacetal. Our synthetic strategy features two cycloadditions ([4+2] and [5+2]) to forge the tetracyclic core and Achmatowicz rearrangement for the preparation of the cyclization substrates containing B and E rings.