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[求助]
帮忙翻译一下这个合成实验步骤
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Synthesis of Ginkgotoxine-5'-Glucoside Acetic anhydride (0.8 mL) was added dropwise to a solution of ginkgotoxin (1.90 g), triethylamine (1.6 mL), and dimethylaminopyridine (0.38 g) in dichloromethane (60 mL), under ice-cooling. The mixture was stirred under ice-cooling for 20 min, and then the solvent was evaporated in vacuo. The residue was diluted with saturated sodium hydrogen carbonate and extracted with ethyl acetate. The organic layer was washed with saturated sodium hydrogen carbonate and dried over anhydrous sodium sulfate. After evaporation of the solvent, the crude product was purified by column chromatography on silica gel, using chloroform/methanol (50/1, v/v) as an eluent, to give 3-acetoxy-5-hydroxymethyl-4-methoxymethyl-2-methylpyridine (ginkgotoxin-3-acetate) (1.16 g) as a pale yellow oily product. IR (neat):3300 (OH), 1775 (C55O). 1H-NMR (CDCl3):2.34 (3H, s, CH3CO-), 2.36 (3H, s, 2-CH3), 3.33 (3H, s, 4-CH2OCH3), 4.45 (2H, s, 4-CH2OCH3), 4.64 (2H, s, 5-CH2OH), 8.31 (1H, s, 6-H). A mixture of ginkgotoxin-3-acetate (1.82 g), 2, 3, 4, 6-tetra-O-acetyl-a- D-glucopyranosyl bromide (3.99 g),[12] silver carbonate (2.68 g), and Molecular Sieves 3A (14 g) in dry dichloromethane (50 mL) was refluxed for 3 days in the dark. After removal of insoluble materials by filtration, the solvent was evaporated in vacuo. The crude product was purified by column chromatography on silica gel using benzene/acetone (5/1) and recrystallization from ethyl acetate/hexane, to give ginkgotoxin-50-glucoside pentaacetate (2.0 g) as colorless prisms. mp: 126–1278C. IR (nujol):1750 (C55O). 1H-NMR (CDCl3):1.96, 1.98, 1.99, 2.08, 2.33 (each 3H, s, CH3CO-), 2.39 (3H, s, 2-CH3), 3.26 (3H, s, 4-CH2OCH3), 3.67 (1H, ddd, J ¼ 2.3, 4.6, 10.0 Hz, Glc H-5), 4.14 (1H, dd, J ¼ 2.3, 12.0 Hz, Glc H-6), 4.24 (1H, dd, J ¼ 4.6, 12.0 Hz, Glc H-6), 4.36, 4.40 (2H, AB, J ¼ 12.0 Hz, 4-CH2O-), 4.54 (1H, d, J ¼ 8.0 Hz, Glc H-1), 4.69, 4.97 (2H, AB, J ¼ 12.6 Hz, 5-CH2O-), 4.98-5.09 (3H, m, Glc H-2, H-3, H-4), 8.31 (1H, s, 6-OH). Potassium hydroxide, 2M(2 mL) was added to a solution of ginkgotoxin- 50-glucoside pentaacetate (222 mg) in methanol (4 mL). The mixture was stirred at room temperature overnight in the dark. The pH was adjusted to 8–9 with acetic acid, and the solvent was evaporated in vacuo. The residue was dissolved in a minimal amount of water and was applied to a reversedphase column (240 15 mm) equilibrated with water. After washing the column with water, elution was accomplished with 3% methanol. The eluate was lyophilized to give ginkgotoxin- 50-glucoside as white crystals (115 mg). mp: 128–1338C. IR (nujol):3400 (OH). 1H-NMR (D2O-DMSOd6): 2.32 (3H, s, 2-CH3), 2.92-3.11 (4H, m, Glc H-2, H-3, H-4, H-5), 3.23 (3H, s, 4-CH2OCH3), 3.42 (1H, dd, J ¼ 5.7, 11.7 Hz, Glc H-6), 3.65 (1H, dd, J ¼ 1.7, 11.7 Hz, Glc H-6), 4.13 (1H, d, J ¼ 7.4 Hz, Glc H-1), 4.52, 4.55 (2H, AB, J ¼ 11.4 Hz, 4-CH2O-), 4.54, 4.78 (2H, AB, J ¼ 12.0 Hz, 5-CH2O-), 7.92 (1H, s, 6-H). UV lmax (5mM potassium phosphate, pH 2.5) nm:291. ESI-MS m/z:346 [M þ H]þ. |
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