文摘
Two new approaches for the construction the ABF ring systems of 7,17-seco-type C19-diterpenoid alkaloids have been successfully developed by using free radical cyclization and intramolecular nitrile oxide cycloaddition, respectively, as the key steps. Both methods would probably provide alternative strategies for the elaboration of AEF-rings in the total synthesis of 7,17-seco-type C19-diterpenoid alkaloids based on our previously prepared BCD ring systems.