A Facile Synthesis of the Angucyclinone Antibiotic (+)-Rubiginone B2 Involving the BF3-Mediated Diels-Alder Reaction of Juglone

A short synthesis of (+)-rubiginone B 2 is reported. The BF 3 -mediated Diels-Alder reactionof jugloneand (R)-3-methyl-1-vinylcyclohexene followed by aromatization gave the anthraquinoneas the desired regioisomer, whichwas converted into the target antibiotic after a two-step operation.