Enantioselective Total Synthesis of (−)-Cyathin B2: A Desymmetric Double-Allylboration Approach

A powerful Pt-catalyzed asymmetric diboration/desymmetric double-allylboration cascade reaction has been developed for the construction of synthetically useful, densely functionalized hydrindanes with five stereocenters, including three quaternary ones, in good yields and excellent enantiomeric excess (ee) values within a single synthetic operation. A unified strategy utilizing this key tandem methodology enabled the concise asymmetric total synthesis of cyathane diterpene (−)-Cyathin B2 in 14 steps from commercially available starting materials, thereby demonstrating its remarkable potential in the synthesis of hydrindane-containing natural products and pharmaceuticals.