Total Synthesis and Structural Determination of the Dimeric Tetrahydroxanthone Ascherxanthone A.

The first total synthesis of the dimeric tetrahydroxanthone ascherxanthone A has been accomplished. This synthetic strategy features (1) enantioselective intramolecular allylic C-H oxidation to construct a core chiral chromane, (2) intramolecular aldol reaction/dehydration to form the enone group, and (3) intermolecular Suzuki-Miyaura coupling to connect two monomeric tetrahydroxanthones. This synthetic work allowed us to determine the axial chirality of the 2,2'-biaryl C-C bond and the absolute configuration of the ascherxanthone A. This approach should facilitate the preparation of derivatives and structurally related natural products for medicinal studies.