Synthetic Study on Bicyclic Pyranonaphthoquinone Natural Products: Construction of the Dioxabicyclo[3.3.1]nonene Motif

A concise method for the construction of dioxabicyclo[3.3.1]nonene framework has been developed. This structural motif has recently been identified in hybrid‐type pyranonaphthoquinone‐class natural products. The reaction proceeds in a stereoselective manner under mild conditions. In conjunction with this study, the scalable total syntheses of nanaomycins A and D have been achieved. Based on extensive screening of reaction conditions and nucleophiles, a plausible reaction mechanism is proposed.