Catalytic Asymmetric Total Synthesis of Chimonanthine, Folicanthine, and Calycanthine through Double Michael Reaction of Bisoxindole

Direct access: Sterically hindered vicinal quaternary carbon stereocenters were constructed by catalytic enantio- and diastereoselective double Michael reaction, providing straightforward access to dimeric hexahydropyrroloindole alkaloids. A Mn(4-fluorobenzoate)2/Schiff base complex and a Mg(OAc)2/benzoic acid system were used as catalysts.