Total synthesis of the carbon18-diterpenoid alkaloids neofinaconitine and 9-deoxylappaconitine

The C18- and C19-diterpenoid alkaloids are a family of natural products called norditerpenoids collectively. They are isolated from the plant genera Aconitum and Delphinium, and exhibit pronounced pharmarcological activities including analgesia, antiarrhythmia and anti-inflammation. Their intriguing biological activities and complicated polycyclic core structures prompted us to pursue the synthesis of these natural products.;A convergent synthetic strategy was developed, highlighting a diastereoselective Diels-Alder cycloaddition to assemble all of the carbon atoms required for norditerpenoid alkaloids. An N-acyliminium cyclization and a radical cyclization were enlisted to forge the complete carbocyclic core skeleton. Our approach was successfully applied to the total synthesis of neofinaconitine and 9-deoxylappaconitine.