Synthesis of balsaminone A, a naturally occurring pentacyclic dinaphthofuran quinone

A short synthesis of the natural product balsaminone A, a dinaphthofuran quinone, is described. The key steps of the synthesis are base-induced coupling of 1,4-dihydroxy-2-naphthaldehyde with 2,3-dichloronaphthoquinone to give a pentacyclic dinaphthofuran directly, followed by conversion of the aldehyde into the desired methoxy group via the corresponding phenol. The synthesis, in which the structure of a key pentacyclic intermediate is corroborated by X-ray crystallography, confirms the original structural assignment of the natural product.