Novel stereoselective synthesis of enantiopure (+)-N-Boc-norpandamarilactonine-A, the intermediate for pandamarilactonines

A novel synthesis of enantiopure N-Boc-norpandamarilactonine-A was established by employing a double ring-closing metathesis of a tetraene derivative, as a key step, where two five-membered rings were constructed in one step. N-Boc-Norpandamarilactonine-A was also converted to ent-norpandamarilactonine-A, and subsequently to pandamarilactonine-A and B.