A solution of methyl[(3S)-6-hydroxy-2,3-dihydro-1-benzofuran-3-yl]acetate (0.208 g, 1.00 mmol), (3′-(hydroxymethyl)-6-methyl-4-[3-(methylsulfonyl)propoxy]biphenyl-2-yl)methyl acetate (0.360 g, 1.00 mmol) and tributylphosphine (0.324 g, 1.60 mmol) in toluene (15 mL) was stirred, 1,1′-(azodicarbonyl)dipiperidine (0.404 g, 1.60 mmol) was added, and the mixture was stirred at room temperature for 3 hr under nitrogen atmosphere. Hexane (8 mL) was added to the reaction mixture, the precipitated insoluble substance was filtered off, and the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate:hexane=30:70-70:30) to give the title compound (0.432 g, yield 79%) as a colorless oil.
