Synthetic studies towards volvalerenol A: access to a fully functionalized cycloheptane framework in an asymmetric fashion through the exploitation of C2-symmetry

The enantioselective synthesis of a fully functionalized cycloheptane core of the naturally occurring triterpenoid volvalerenol A, exhibiting pseudo-C2 symmetry, was achieved. Enantioselective enzymatic desymmetrization (EED), asymmetric methallylation, and reductive ring opening of an cyclopropane overbred intermediate were the key reactions to access the cycloheptanone core. Further synthetic manipulations, via a unique “MPV” (Meerwein–Ponndorf–Verley) type reductive ring-opening of an epoxide and other synthetic transformations, afforded two fully functionalized cycloheptane frameworks of the target molecule.