Structural Revision and Biomimetic Synthesis of GoupioloneB

GoupiolonesA and B are unique phenolic compounds with significant DNA-damaging activity. In this study, the structure of goupioloneB was revised on the basis of DFT calculations of the (CNMR)-C-13 chemical shifts and biosynthetic considerations. The dibenzobicyclo[3.2.2]nonane skeleton of the revised structure suggested that goupioloneB was produced by oxidative coupling between catechol and goupioloneA, which was strongly supported by biomimetic synthesis. Furthermore, racemization of goupioloneB was observed during the attempted resolution of its racemic mixture. A plausible racemization mechanism involving -ketol rearrangement is proposed.