To a mixture of No. 5217614, tert-butyl (E)-(2S,3S)-3-[(S)-2-(4-but-2-ynyloxy-phenyl)-1-methoxycarbonyl-ethylcarbamoyl]-2-hydroxy-2-(2-hydroxy-ethyl)-12-oxo-nonadec-4-enoate (150 mg, 0.214 mmol) and dichloromethane (15 mL) were added trifluoroacetic acid anhydride (TFAA, 36 μL, 0.258 mmol), triethylamine (89 μL, 0.642 mmol), and DMAP (1.3 mg, 0.0107 mmol), and the mixture was stirred at room temperature. After being stirred for 3 hours, trifluoroacetic acid anhydride (72 μL, 0.516 mmol) was added again. After confirming the consumption of No. 5217614 tert-butyl (E)-(2S,3S)-3-[(S)-2-(4-but-2-ynyloxy-phenyl)-1-methoxycarbonyl-ethylcarbamoyl]-2-hydroxy-2-(2-hydroxy-ethyl)-12-oxo-nonadec-4-enoate by LCMS, formic acid (5 mL) was added and the mixture was stirred overnight. The solvent was distilled off under reduced pressure. THF (5 mL) and a saturated aqueous solution (0.5 mL) of NaHCO3 were then added and the mixture was stirred at room temperature for 10 minutes. The solvent was distilled off under reduced pressure. The residue was then purified by preparative HPLC. The purified fraction was freeze-dried to obtain the title compound (67 mg, 48% yield, yellow oil).
