Total Syntheses of (±)-Rhodonoids C, D, E, F, and G and Ranhuadujuanine B.

Here we describe the divergent, biosynthetically inspired syntheses of (±)-rhodonoids C-G and (±)-ranhuadujuanine B. The key steps of the syntheses include the construction of the chromene unit through a formal oxa-[3 + 3] annulation and a biomimetic acid-catalyzed ring cyclization. Cationic [2 + 2] cycloaddition is accomplished to form the cyclobutane core of (±)-rhodonoids E and F.