Enantioselective Total Synthesis of (+)-Anthecularin.

An enantioselective total synthesis of (+)-anthecularin, an antiplasmodial and antitrypanosomal sesquiterpene lactone, has been achieved in 3.9% overall yield through 18 steps from a known dibromo alcohol. The key features of the synthesis include an intramolecular Claisen-type cyclization of a formyl-protected hydroxyl lactone to construct a bicyclic intermediate with a quaternary stereogenic center and a stereocontrolled 1,2-addition of vinyllithium to a methoxyethyl-protected spirocyclic hydroxyl enone to install a tetrasubstituted asymmetric center with excellent diastereoselection. This first enantioselective synthesis of anthecularin enabled the determination of its absolute configuration as 2 R, 3 R, 4 S, 8 R.