Lithium hydroxide, monohydrate → methyl 7-[(1R,2R,3R,5S)-5-acetoxy-2-((E)-4,4-difluoro-3-oxo-1-octenyl)-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanate

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Reaction Steps

To a solution of dimethyl (3,3-difluoro-2-oxoheptyl)phosphonate (1) (1.052 g, 4.074 mmol) in 1,4-dioxane (16 ml), lithium hydroxide monohydrate (0.160 g, 3.81 mmol) was added and stirred for approximately 1.2 hours at room temperature. A solution of methyl 7-[(1R,2R,3R,5S)-5-acetoxy-2-formyl-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanate (2) (0.902 g, 2.26 mmol) in 1,4-dioxane (3 ml) and water (0.57 ml) were added thereto, and the mixed solution was heat refluxed for approximately 48 hours. After cooling to room temperature, approximately half of the solvent was evaporated under reduced pressure. Ethyl acetate and water were added to the residue and the solution was stirred, let to stand and then separated into two layers. The aqueous layer was extracted twice with ethyl acetate. The organic layers were combined, sequentially washed with 3% aqueous sodium chloride and saturated aqueous sodium chloride, and then dried with anhydrous magnesium sulfate. After concentration under reduced pressure, the residue was purified by silica gel column chromatography (Fuji Silysia BW-300SP: 36 g; ethyl acetate:hexane=1:4). The fractions containing impurities were re-purified by silica gel column chromatography (Fuji Silysia BW-300SP: 6 g; ethyl acetate:hexane=1:4) to give methyl 7-[(1R,2R,3R,5S)-5-acetoxy-2-((E)-4,4-difluoro-3-oxo-1-octenyl)-3-(2-tetrahydropyranyloxy)cyclopentyl]heptanate (3) (0.671 g; 1.26 mmol; yield: 55.9%).

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