Total Synthesis and Determination of the Absolute Configuration of (+)‐Omaezakianol

The proof of the pudding: The first asymmetric total synthesis of the marine tetracyclic oxasqualenoid (+)-omaezakianol features a convergent olefin cross-metathesis between a monotetrahydrofuran fragment and a triepoxy alkene, and cascade oxacyclizations of a triepoxy alcohol to form the right-hand three ether rings. The total synthesis proved the absolute configuration of (+)-omaezakianol to be that shown.