Concise synthesis of the C15-C38 fragment of okadaic acid, a specific inhibitor of protein phosphatases 1 and 2A

Abstract A marine polyether natural product okadaic acid is known to be a potent and specific inhibitor of protein phosphatases 1 and 2A. Herein, concise synthesis of the C15-C38 fragment of okadaic acid is reported. We investigated two different strategies for the construction of two spiroacetal substructures found in the target compound. The first strategy involved Suzuki-Miyaura coupling for the synthesis of endocyclic enol ethers and subsequent spiroacetalization. The second strategy exploited Suzuki-Miyaura coupling for the synthesis of exo-olefins as the precursor of spiroacetals. An alkynylaluminum-anomeric sulfone coupling effectively assembled the key spiroacetal substructures and completed the target compound.