The synthesis of kibdelone C, a polycyclic natural xanthone isolated from a soil actinomycete, was achieved through a convergent approach. A 6π-electrocyclization was applied to construct the highly substituted dihydrophenanthrenol fragment (B–C–D ring). InBr3-promoted lactonization was employed to build the isocoumarin ring, which served as a common precursor for the formation of isoquinolinone ring