Preparation of Seven-Membered Carbocycles Using Ring-Closing Metathesis Reaction and Application to Syntheses of Tormesol and Cyathane Skeleton

Abstract Various precursors were synthesized and were reacted with the Grubbs reagent as well as the second generation Grubbs reagent to cyclize them into seven-membered carbocycles with di- or tri-substituted double bonds. These reactions were used to synthesize (−)-tormesol, which is an enantiomer of sphenolobane-type diterpene that was isolated from Halimium viscosum, and a basic skeleton of cyathane-type diterpene.