Development of a scalable synthesis of a common eastern tricyclic lactone for construction of the nodulisporic acids

A scalable, second-generation synthesis of the densely functionalized eastern tricyclic lactone (+)-6, a common intermediate, for construction of the nodulisporic acids has been achieved. Modifications to the first-generation route now permit access to (+)-6 in 17 steps with an overall 16.5% yield. Key carbon-carbon bond constructions include a Kirk-Petrow (phenylthio)methylation, a Sc(OTf)(3)-catalyzed hydroxymethylation, a Stille carbonylation, and a Koga three-component, conjugate addition-alkylation sequence.