Formal Synthesis of (±)-Platensimycin

Reductive alkylation of 5-methoxy-1-tetralone (<b>6</b>) with 2,3-dibromopropene gave an equilibrium mixture of bicyclic diones <b>7</b> (51%) and <b>8</b> (35%). Radical cyclization of <b>7</b> afforded tricyclic dione <b>5</b> (84%), which was reduced, cyclized, and dehydrated to give tetracyclic alkene <b>13</b> in 63% yield. Allylic oxidation of <b>13</b> with SeO<sub>2</sub> and activated MnO<sub>2</sub> afforded enone <b>2</b> in 85% yield, thereby completing a short formal synthesis of (±)-platensimycin.