Photochemical Approaches to the Bilobalide Core

Bilobalide is a tetracyclic sesquiterpene containing three contiguous γ‐lactone rings and an unusual tert ‐butyl group, which is found in the leaves of the ginkgo tree ( Ginkgo biloba ). Three different photochemical approaches towards bilobalide's unique skeleton are presented. A meta photocycloaddition, a [2 + 2] photocycloaddition, and a Paternò–Büchi‐reaction were chosen as the respective key steps.