To a solution of 929 mg (2.24 mmol) of the product of Step L in benzene were added oxalyl chloride (234 mL, 2.69 mmol) and one drop of DMF at 0° C. The solution was stirred at rt for 45 minutes. After concentration the residue was dissolved in CH2Cl2 (10 mL). The solution was added to a solution of tert-butyl alcohol (253 mL, 2.69 mmol) and Et3N in CH2Cl2 (10 mL) at 0° C. The solution was stirred at rt for 3 hours. The mixture was poured into EtOAc (50 mL) and washed with H2O (1×) and brine, and dried over anhydrous MgSO4. Concentration gave 778 mg of the title compound as a slightly yellow glass.
