Synthetic Studies of Ganoderma-Derived Meroterpenoid Dimers

The Ganoderma genus is a rich source of structurally diverse meroterpenoids. Owing to their intriguing structures and significant biological activities, Ganoderma-derived meroterpenoids (GMs) are attractive synthetic targets. Based on their structural characteristics, GMs can be classified into three subclasses: linear, polycyclic, and dimeric GMs. While several polycyclic GMs have been synthesized multiple times, synthetic studies on dimeric GMs remain limited. Ganodilactone, spirocochlealactone A, and dimercochlearlactones I and J are dimeric GMs isolated from G. leucocontextum and G. cochlear. These compounds feature a common 5’H-spiro[chromane-4,2’-furan]-2,5’-dione ring system bearing two consecutive tetrasubstituted carbon stereogenic centers, which make them synthetically challenging. In this account, our efforts toward the first total syntheses of these dimeric GMs are summarized. The core skeleton of these natural products was efficiently constructed through intramolecular 1,4-addition reaction as a key step. The findings of this study will support synthetic, biological, and medicinal chemistry studies on these natural products and their derivatives.