Potassium carbonate (0.11 g) was added to a solution of the compound obtained from step c above (0.3 g) in methanol (4 mL) and tetrahydrofuran (4 mL) at 0° C. The reaction mixture was stirred at room temperature for 3 hours. The solvents were evaporated, and the residue was taken into water and ethyl acetate. The organic layer was washed with water and brine solution, and dried over anhydrous sodium sulphate. The solvent was evaporated under reduced pressure to obtain a residue which was purified by column chromatography over silica gel using 10% methanol in dichloromethane as eluant to afford the title compound (0.020 g).
