Sulfuric Acid → methyl(1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[4-chloro-3-[[4-(2,2,2-trifluoro ethoxy)phenyl]methyl]phenyl]-6,8-dioxabicyclo[3.2.1]octane-1-carboxylate

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Reaction Steps

To a solution of (1S,2S,3S,4R,5S)-2,3,4-tribenzyloxy-5-[4-chloro-3-[[4-(2,2,2-trifluoroethoxyl)phenyl]methyl]phenyl]-6,8-dioxabicyclo[3.2.1]octane-1-carboxylic acid 18a (0.74 g, 0.95 mmol) in methanol (40 mL) was added concentrated sulphuric acid (0.75 mL, 13.8 mmol) at 0° C. The mixture was warmed up to room temperature and stirred for 12 hours, and then adjusted with saturated aqueous sodium bicarbonate to pH 8 and concentrated in vacuo to remove most of the solvent. To the residue was added water (50 mL). The resulting mixture was extracted with ethyl acetate (50 mL×3). The combined organic layers were washed with saturated aqueous sodium chloride (80 mL), dried over anhydrous sodium sulfate and filtrated. The filtrate was concentrated in vacuo to give the title compound 18b as orange-yellow oil (0.6 g, 81.1%). This material was not further purified. The compound was characterized by the following spectroscopic data: 1H NMR (600 MHz, CDCl3) δ(ppm): 7.45 (d, 1H), 7.41-7.35 (m, 2H), 7.34-7.27 (m, 6H), 7.24 (m, 4H), 7.20 (t, 1H), 7.15 (t, 2H), 7.08 (d, 2H), 6.85 (d, 2H), 6.76 (d, 2H), 4.82 (m, 2H), 4.77 (d, 1H), 4.61 (d, 1H), 4.51 (d, 1H), 4.25 (m, 3H), 4.17 (t, 2H), 4.07 (d, 1H), 3.99 (m, 2H), 3.84 (d, 1H), 3.72 (d, 1H), 3.69 (s, 3H).

Provenance & Evidence