No. 5327507 Compound C (50.8 g, 59.2 mmol) was dissolved in acetonitrile (560 mL), and then an aqueous solution of 0.5 M citric acid (249 mL, 125 mmol) was added to the solution, which was stirred at 60° C. for 2.5 hours. After confirming that inner temperature had returned to room temperature, a mixture of a saturated aqueous solution of sodium chloride (51 mL) and water (813 mL) was added. The solution was extracted with 20% ethyl acetate/n-hexane (457 mL) 3 times. The organic layers were combined, then washed twice with a saturated aqueous solution (230 mL) of sodium chloride, dried over anhydrous sodium sulfate, and filtered. The solvent was then distilled off under reduced pressure and the residue was purified on Biotage (silica gel, n-hexane/acetone) to obtain 23.6 g (33.7 mmol, 57% yield) of No. 5217614 (Compound D).
