Synthesis of Cyclosiphonodictyol A and Its Bis(sulfato).

The first synthesis of the marine benzoxepane hydroquinone cyclosiphonodictyol A and its bis(sulfato) from commercial (+)-sclareolide is reported. The key steps of the synthetic sequence (11 steps, 46% global) are the nucleophilic attack of a hindered tertiary alkoxide, a ring-closing metathesis reaction, and the Diels-Alder cycloaddition of a dienol acetate.