Isopropenyl acetate → 2-Methoxy-3,17-diacetoxyestra-1,3,5(10),14,16-pentaene

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Under nitrogen, toluenesulfonic acid monohydrate (0.1 g, 0.53 mmol) was added to a solution of 2-Methoxyestra-1,3,5(10),15-tetraen-3-ol-17-one prepared in Example 3 (0.25 g, 0.84 mmol), isopropenyl acetate (5 mL, 45.15 mmol) and acetic anhydride (5 mL, 53 mmol) and the mixture was heated to reflux for 6 h. At the end of that time, analysis by tlc (2% acetone in CH2Cl2) indicated a complete reaction. The reaction was cooled to room temperature, poured into ice water (˜100 mL) and stirred for 1 h. The mixture was extracted with methylene chloride (3×). The organic fractions were washed with water (1×), saturated sodium bicarbonate solution (1×) and water (1×), filtered through anhydrous sodium sulfate, combined and concentrated in vacuo. The residue was crystallized from methanol to give the pure diacetate (17) (0.259 g, 80.8%).

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