Methanol → Costatolide

Participants

Reaction Conditions

Reaction Steps

To a solution of (−)-calanolide A (341 mg, 0.922 mmol) in anhydrous methylene chloride (5 mL) at −78° C. under N2 was added a solution of diethylamidosulfur trifluoride (DAST, 178 mg, 1.11 mmol) in methylene chloride (1 mL) and the resulting yellow solution stirred at −78° C. for 4 hours. The reaction was quenched with 0.5 mL methanol, then allowed to warm to room temperature. The solution was diluted with methylene chloride (20 mL), then washed with water (50 mL) and saturated brine (50 mL). After drying over magnesium sulfate, the solution was filtered and evaporated to provide a light yellow solid. TLC analysis (silica gel, 3% methanol in methylene chloride) showed two components, one fast-moving and one slow. The material was chromatographed through 80 g silica gel, eluting with 1% methanol in CH2Cl2, and the fractions containing the respective components combined and evaporated to afford 198 mg (61% yield) of compound 22 and 75.3 mg (22%) of (−)-calanolide B.

Provenance & Evidence