A remarkably short (four steps, 31% overall yield) enantioselective synthesis of the structurally unique C 2-symmetric tetracyclic triterpene (+)-α-onocerin (1) has been developed. The brevity of this mechanism depends on the assembly of four fragments (two molecules of a chiral epoxy ketone and two molecules of vinyllithium) to generate the chiral bis-epoxide 4 in one step, and on the efficient formation of all four carbocyclic rings in one ...