Enantioselective synthesis of tetraponerines by Pd- and Ru-catalyzed domino reactions

An enantioselective synthesis of tetraponerines T4, T6, T7, and T8 in 24-36 % overall yield is described. Key steps in this synthesis are a Pd-catalyze d domino allylation and a Ru-catalyzed ring rearrangement. The effect of di fferent substituents on the equilibrium of the metathesis rearrangement has been investigated. To complete the synthesis a sequence of Wacker oxidatio n and Takai olefination was used. The preparation of four representative te traponerines differing in stereochemistry, ring size, and side chain employ ing five metal-organic reactions clearly demonstrates the efficiency of tra nsition metals in organic synthesis.