Chiral Building Blocks for the Synthesis of Triquinane Sesquiterpenes: Derivatives of 2‐Methylbicyclo[3.3.0]octan‐3‐ol from Catalpol

The synthesis of enantiomerically pure triquinane sesquiterpenes is of interest owing to the remarkable biological activity of some of these natural products. The compounds 1–3, which may be prepared from naturally occurring catalpol on a gram scale, are suitable as chiral building blocks. The absolute configuration of (+)-3, a precursor of (−)-coriolin, was established by X-ray structure analysis.