Stereoselective Synthesis of trans-Fused 7,6,6,7-Membered Tetracyclic Ether, Corresponding to the EFGH-Ring of Gambierol and the BCDE-Ring of Gambieric Acids

Stereoselective synthesis of a trans-fused 7,6,6,7-membered tetracyclic ether, corresponding to the EFGH-ring of gambierol and the BCDE-ring of gambieric acids, was efficiently accomplished via a two-directional approach. The key reactions were SmI(2)-induced double cyclization for construction of the F- and H-rings and SmI(2)-induced cyclization followed by ring expansion for construction of the E-ring.