After stirring at 80 °C for 14 hours, the reaction apparatus was removed from the oil bath and allowed to cool to room temperature. Once at room temperature, O2 was bubbled through the reaction for 30 minutes. Following this, the reaction was concentrated under reduced pressure by rotary evaporation to give a yellow solid, which was dissolved in EtOAc (50 mL) and water (100 mL). The layers were separated, and the aqueous layer was extracted with EtOAc (2 x 50 mL). The combined organic extracts were washed with brine (50 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure by rotary evaporation to give a yellow viscous oil. Purification by flash column chromatography on silica gel (2% Et2O/hexanes to 10% Et2O/hexanes) afforded 4-1 (5.1 g, 16% over two steps) as a colorless solid.