Divergent Synthesis of Antiviral Diterpenes Wickerols A and B

Wickerols A and B
are diterpene natural products that have a novel
fused 6–5–6–6 ring framework and exhibit potent
antiviral activity against the H1N1 type A influenza virus. Herein,
we report a divergent synthesis of wickerols A and B in 16 and 15
steps, respectively, from commercial sitolactone. The key reactions
of the synthesis are a SmI2-mediated intramolecular ketone–allylic
acetate reductive cyclization, a Claisen rearrangement, and an intramolecular
alkylation/aldol reaction that rapidly assembled the compact tetracyclic
core framework in a stereocontrolled manner. The work described herein
allowed us to confirm the absolute configurations of wickerols A and
B.