Quadrane Sesquiterpenes: Natural Sources, Biology, and Syntheses

Quadranes, discovered with the isolation of (-)-quadrone in 1978, are biologically active naturally occurring sesquiterpenes featuring a distinctive set of bi- to tetracyclic ring systems. The available data for this family of natural products, including isolation data, biosynthetic considerations, a comprehensive compilation of the reported biological activities, and an exhaustive survey of the synthetic work in this area so far, are critically analyzed.