Total Synthesis of Isoriccardin C and Isoriccardin D Based on a Hydroxyl-Directed Palladium-Catalyzed Intramolecular C–H Alkenylation

A concise, nine-step total synthesis of isoriccardin C and isoriccardin D has been developed. The strategy centers on the sequential installation of the four aromatic rings of the backbone by using three key transformations: Suzuki coupling, Wittig olefination, and Ullmann coupling. The pivotal step is a palladium(II)-catalyzed, intramolecular ortho-alkenylation that forges the 18-membered macrocyclic core. This streamlined route enables the total synthesis with minimal reliance on protecting groups, and its modular nature offers a versatile platform for the construction of structural analogues.