To a solution of the product from Step 5 (0.82 g, 1.9 mmol) in dichloromethane (15 mL) cooled at 0° C. was added a solution of boron tribromide in heptane (1.0 M, 3.8 mL, 3.8 mmol). The reaction was stirred at 25° C. for 30 min and then poured into aqueous sodium bicarbonate. The aqueous layer was extracted with ethyl acetate. The combine organic phase was washed with brine, dried over magnesium sulfate and concentrated. The residue was purified by chromatography on silica gel to give the title product.
