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) was dissolved in 3 mL of dichloromethane, followed by addition of methanesulfonyl chloride (13 mg, 0.11 mmol) and triethylamine (18 mg, 0.18 mmol). The reaction solution was stirred for 2 hours. The resulting solution was added with 30 mL of ethyl acetate. 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 and the residue was purified by TLC with elution system A to obtain the title compound methyl 2-((S)-6-((2′,6′-dimethyl-4′-(((S)-1-(methylsulfonyl)pyrrolidin-3-yl)oxy)biphenyl-3-yl)methoxy)-2,3-dihydrobenzofuran-3-yl)acetate 8b (40 mg, yield 77.0%) as a colorless oil.
