Asymmetric Total Synthesis of Naphthospironone A

Naphthospironone A, a polyhydroxy cagelike bioactive natural product, was synthesised for the first time in this study. The spiro[bicyclo[3.2.1]octane‐pyran] core was constructed by an acid‐promoted epoxide‐opening lactonisation and a base‐induced intramolecular aldol‐type cyclisation. Naphthospironone A, a cytotoxic and antibacterial natural product, was synthesised for the first time. The key to construction of its spiro[bicyclo[3.2.1]octane‐pyran] core was a two‐step sequence involving hydrogenolytic debrominative olefin migration followed by a base‐induced intramolecular aldol‐type cyclisation.