To the mixture of (E)-(2S,3S)-3-[(S)-2-(4-butoxy-phenyl)-1-methoxycarbonyl-ethylcarbamoyl]-12,12-difluoro-2-hydroxy-2-(2-methoxy-ethyl)-nonadec-4-enoic acid (No. 5514403, 50 mg, 0.0731 mmol), sodium iodide (16.4 mg, 0.110 mmol), sodium bicarbonate (7.4 mg, 0.877 mmol) and the DMF (1 mL) was added commercially available 4-chloromethyl-5-methyl-1,3-dioxol-2-one (15.9 μL, 0.145 mmol) at room temperature, and the mixture was stirred as it was for 22 hours. After confirming the consumption of the starting materials by LCMS, the reaction solution was filtered through a syringe filter, and purified as it was by preparative HPLC. The purified fraction was freeze-dried to obtain the title compound (48 mg, 83% yield) as yellow oil.
