To a solution of the product from step 4 (0.8 g, 2.63 mmol) in dichloromethane (7.6 mL) was added triethylamine (0.78 mL, 5.60 mmol) and t-butyl bromoacetate (0.45 mL, 3.05 mmol). The resulting solution was stirred at 30° C. overnight. The reaction mixture was poured into water/dichloromethane (50 mL/50 mL). The crude residue was extracted into dichloromethane. The organic portion was washed with water (50 mL), washed with brine (50 mL), dried over anhydrous Na2SO4, filtered and concentrated in vacuo. The crude product was purified by silica gel flash chromatography using hexane/EtOAc (gradient system) to give the title compound (0.83 g, 75%);
