Synthesis of ()-Frondosin B

Significance

Frondosin B exhibits anti-HIV, anti-inflammatory, and anti-tumor activity. The authors utilize a microwave-induced 5-exo-dig cyclization (A→B) followed by in situ Claisen rearrangement (B→C) to produce the seven-membered ring. This short synthesis of frondosin B was accomplished in 38% overall yield (7 steps).