Formal synthesis of (±)-galanthamine and (±)-lycoramine using Rh(I)-catalyzed [(3 + 2) + 1] cycloaddition of 1-ene-vinylcyclopropane and CO.

An efficient strategy using Rh(I)-catalyzed [(3 + 2) + 1] cycloaddition of 1-ene-vinylcyclopropane and CO as a key step to build the cis-hydrodibenzofuran skeleton has been developed and applied for the formal synthesis of (±)-galanthamine and (±)-lycoramine.