Asymmetric Synthesis of Rugulotrosin A.

A new approach was developed to construct the tetrahydroxanthone by a Knoevenagel condensation/6π-electronic cyclization/aromatization cascade starting from readily available cyclohexane-1,3-diones and unsaturated aldehydes. This strategy provides a new solution for the preparation of monomeric tetrahydroxanthones bearing different functional groups at C-12. As a synthetic application, the asymmetric formal synthesis of rugulotrosin A was achieved.