Three-component coupling via the squarate ester cascade as a concise route to the bioactive triquinane sesquiterpene hypnophilin.

[reaction: see text] A squarate ester cascade is used to provide in one step, via the coupling of three reactants, a highly oxygenated linear triquinane product. The latter is transformed in nine steps into hypnophilin. The access route involves a combination of chlorination, reduction, dehydration, and oxidation maneuvers in the proper sequence.