Perchloric acid (0.4 mL) was added to a solution of the compound obtained from step f above (0.5 g) in acetonitrile (4 mL) and water (0.8 mL) at room temperature. The reaction mixture was heated to 55° C. for 30 minutes. The reaction mixture was then quenched using sodium bicarbonate solution. The solvents were evaporated under reduced pressure. The residue thus obtained was taken up in ethyl acetate and water. The organic layer was separated, washed with water and brine solution, and dried over anhydrous sodium sulphate. The solvent was concentrated under reduced pressure to yield the title compound (0.51 g).
