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With sulfuric acid; acetic anhydride; sodium hydrogencarbonate; In pyridine; methanol; hexane; chloroform; acetic acid; ethyl acetate; |
Example 13 1-O-Acetyl-2,3,5-tri-O-benzoyl-beta-L-ribofuranose (5) To a solution of <strong>[24259-59-4]L-<strong>[24259-59-4]ribose</strong></strong> (25.0 g, 166.66 mmol) in MeOH (300 mL), was added 25 mL of sat. methanolic hydrogen chloride and stirred at room temperature for 6 h. The reaction was complete after 6 h as indicated by TLC using CH2 Cl2/ MeOH 9:1. After completion of the reaction, dry pyridine (30 mL) was added and the solvents were evaporated. To the residue another 30 mL of pyridine was added and evaporated to dryness. The residue was dissolved in dry pyridine (200 mL) and CH2 Cl2 (150 mL) then cooled to 0 ° C. Benzoyl chloride (96.26 mL, 830.12 mmol) was added drop-wise and stirred at room temperature overnight. TLC using hexane/ethyl acetate (7:3), indicated completion of the reaction. The solvents were evaporated and the residue dissolved in CHCl3 (300 mL), and washed with H2 O (200 mL) and sat. NaHCO3 (200 mL), and dried over anhydrous Na2 SO4. After evaporating the CHCl3, the residue was co-evaporated with toluene to give an oily residue. The residue was dissolved in AcOH (200 mL), acetic anhydride (85.0 mL; 770.9 mmol) and sulfuric acid (4.46 mL; 83.29 mmol). The reaction mixture was stirred at room temperature overnight, after which time TLC (hexane/ethyl acetate 7:3) indicated completion of the reaction. The solvents were evaporated in vacuo and the residue that obtained was co-evaporated with toluene. The brown residue was triturated with EtOH to give light brown crystals. Filtration of the solid and recrystallization from EtOH gave 1-O -acetyl-2,3,5-tri-O-benzoyl-L(+)-glucofuranose 40.5 g (48.0percent) as white crystals: mp 125-125° C.; 1 H NMR (CDCl3) delta 4.49 (m, 1H, C5' H), 4.77 (m, 2H, C4' H and C5' H), 5.80 (d, 1H), 5.93 (m, 1H, C2' H), 6.43 (d, 1H, C1' H, J1,2 =1.5 Hz) and 7.30-8.09 (m, 15H, PhH). |