The crude methyl 2-((S)-6-((2′,6′-dimethyl-4′-((S)-pyrrolidin-3-yloxy)biphenyl-3-yl)methoxy)-2,3-dihydrobenzofuran-3-yl)acetate 8a (45 mg, 0.09 mmol) were dissolved in 3 mL of dichloromethane, followed by addition of acetic anhydride (13 mg, 0.11 mmol) and triethylamine (18 mg, 0.18 mmol). The reaction solution was stirred for 2 hours. The resulting solution was mixed with 20 mL of dichloromethane. The organic phase was washed with saturated sodium chloride solution (30 mL), dried with anhydrous magnesium sulphate, and filtered. The filtrate was concentrated under reduced pressure to obtain the crude title compound methyl 2-((S)-6-((4′-(((S)-1-acetylpyrrolidin-3-yl)oxy)-2′,6′-dimethylbiphenyl-3-yl)methoxy)-2,3-dihydrobenzofuran-3-yl)acetate 9a (45 mg, yield 92.5%) as a colorless oil.
