Diastereomeric Resolution of a Racemic Biarylboronic Acid and Its Application to Divergent Asymmetric Total Syntheses of Some Axially Chiral Natural Products

The asymmetric total syntheses of deshydroxytetramethylcupressuflavone and desmethylkotanin and the synthesis of a key intermediate in the previous synthesis of hibarimicinone are described using an axially chiral biarylboronic acid, prepared by the diastereomeric resolution of the corresponding rac-boronic acid, as a common intermediate. Conversion of the boronic acid moiety into either a hydrogen atom or a hydroxy group by protodeboronation or oxidation enabled us to complete the total syntheses of deshydroxytetramethylcupressuflavone and desmethylkotanin and synthesis of a key intermediate in the previous total synthesis of hibarimicinone, respectively.