A solution of the product from Step C (8.50 g, 26.5 mmol) in ethyl acetate (250 mL) was vigorously stirred at 0° C. with saturated sodium bicarbonate (150 mL). Chloroacetyl chloride (2.33 mL, 29.1 mmol) was added, and the reaction stirred at ) 0° C. for 1 h. The layers were separated, and the ethyl acetate phase was washed with saturated brine, and dried over magnesium sulfate. The crude product was dissolved in DMF (300 mL) and cooled to 0° C. under nitrogen. Sodium hydride (1.79 g, 60% dispersion in oil, 44.9 mmol) was added portionwise to maintain moderate hydrogen evolution. After 30 min, an additional amount of sodium hydride was added (0.8 g). The reaction was stirred another 30 min, then quenched with saturated ammonium chloride. The DMF was distilled in vacuo, and the residue partitioned between ethyl acetate and water. The organic phase was washed with water, saturated brine, and dried over magnesium sulfate. The crude product was chromatographed on silica gel with 20-30% ethyl acetate in hexane to obtain the title compound.
