Succinic anhydride → Salvinorin A

To Salvinorin B (190 mg, 0.487 mmol) and succinic anhydride (112 mg, 2.5 eq) suspended in dichloromethane (5 ml) at 0° C. was added DBU (218 pl, 3 eq) dropwise. The mixture was stirred at 0° C. for 15 mins, washed with 3% citric acid (5 ml), saturated NaHCO3 solution (5 ml) and brine (5 ml). The mixture was dried over sodium sulfate, filtered and evaporated to dryness. The crude residue was purified by column chromatography (silica gel: CH2Cl2 to 5% MeOH in CH2Cl2) to give salvinorin hemisuccinate (130 mg, 54%).