Dimethoxymethane → (3R,5S)-5-[(R)-2-Benzyloxy-1-hydroxyethyl]-3-ethyldihydrofuran-2-one

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Reaction Steps

335 ml of a solution of a sodium tetraborate buffer solution (0.05 M) in a 0.4 mM disodium ethylenediaminetetraacetate aqueous solution, 0.503 g of tetrabutylammonium bisulfate (1.48 mmol) and 8.63 g of 1,2:4,5-di-O-isopropylidene-β-D-erythro-2,3-hexodiuro-2,6-pyranose (33.4 mmol) were added to 8.30 g of (2R,4E)-6-benzyloxy-2-ethylhex-4-enoic acid obtained in Example (106b) (33.5 mmol) in a mixed solvent of acetonitrile (167 ml) and dimethoxymethane (333 ml) at room temperature, and the mixture was stirred for 10 minutes. The reaction mixture was cooled in an ice bath. Then, a solution of 28.4 g of Oxone (trade mark) (46.1 mmol) in a 0.4 mM disodium ethylenediaminetetraacetate aqueous solution (168 ml) and a solution of 26.7 g of potassium carbonate (193 mmol) in water (168 ml) were separately added dropwise over four hours. The mixture was stirred at the same temperature for one hour and then diluted with 100 ml of water, followed by extraction with ethyl acetate. Then, the organic layer was washed with brine and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (elution solvent:n-hexane/ethyl acetate=6/1-1/1) to obtain 6.80 g of the title compound (total yield over two steps: 70%).

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