Stereoselective Synthesis of the Decahydrofluorene Core of the Hirsutellones

A stereoselective synthesis of the decahydrofluorene core of the hirsutellones was accomplished in eight steps and in 43% overall yield. The key step of the synthesis is the highly stereoselective intramolecular Diels–Alder cyclization of the siloxacyclopentene-constrained tetraene 1.