First studies directed towards the diastereoselective synthesis of the BCD tricyclic core of brownin F

The BCD tricyclic core of brownin F was prepared in eight synthetic operations for the first time. Our synthesis features a diastereo-, chemo- and regioselective intramolecular [3 + 2] cycloaddition between a cyclic carbonyl ylide and a gamma-alkylidenebutenolide.