A General Entry to Ganoderma Meroterpenoids: Synthesis of Lingzhiol via Photoredox Catalysis

Ganoderma meroterpenoids are a fungal-derived hybrid natural product class containing a 1,2,4-trisubstituted benzene ring and a polycyclic terpenoid part. The representatives applanatumol E, H and I, lingzhilactone B and meroapplanin B share the same bicyclic lactone moiety connected to the arene via a flexible C2-linker. This flexibility is lost for lingzhiol as the b-position of the lactone is fused to the arene to form a tetralone subunit. Employing a diastereoselective iodocarbocyclization and a photo-Fries rearrangement as the key-steps enabled a general entry to these natural products. For the synthesis of the tetracyclic framework of lingzhiol, we made use of a powerful photoredox oxidative decarboxylation/Friedel–Crafts sequence.