Total Syntheses of (±)-Rhodonoids A and B and C12-epi-Rhodonoid B

Total syntheses of (±)-rhodonoids A and B and C12- epi -rhodonoid B are described here. A unified strategy employed in these syntheses is an intramolecular oxa -[3 + 3] annulation for accessing the chromene unit. A Fe(OTf) 3 -promoted diastereoselective cationic [2 + 2] cycloaddition and a photochemical [2 + 2] cycloaddition were featured to construct the cyclobutane core of (±)-rhodonoids A and B and C12- epi -rhodonoid B, respectively. Fe(OTf) 3 also leads to an interesting bridged tetracycle, which was unambiguously confirmed by single crystal X-ray analysis.