Synthetic studies on cyathins:: Enantioselective total synthesis of (+)-allocyathin B2

[Graphics] The enantioselective total synthesis of (+)-allocyathin B-2 has been achieved. Our approach features a convergent enantioselective construction of the 5-6-7 tricyclic core system using the originally developed chiral building blocks via asymmetric catalysis, the intramolecular aldol reaction in high yield, successful samarium diiodide-mediated ring expansion, and a newly developed double-bond installation method.