[(2S,3S,4S)-5-acetyloxy-3,4-dibenzoyloxyoxolan-2-yl]methyl benzoate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of diethyl imidazole-4,5-dicarboxylate (2.65 g, 12.50 mmol) and ammonium sulfate (50 mg) was heated at reflux at 135° C. for 6 h with hexamethyldisilazine (50 mL). The reaction mixture was evaporated to dryness and the residue was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid that obtained was dried in vacuo for 6 h and used for the next step without further characterization. To a solution of the above residue (12.5 mmol) in 1,2-dichlorethane (60 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (5.06 g, 10 mmol) and tin tetrachloride (1.68 mL, 14.16 mmol) at 10° C. The reaction mixture was stirred under the atmosphere of argon at room temperature for 6 h. The reaction was checked by TLC using hexane and ethyl acetate (7:3). TLC indicated no starting material remained. The reaction mixture was diluted with dichloromethane (200 mL). The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. The residue was dissolved in dichloromethane (100 mL) and filtered through celite to remove tin salts. After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol and filtered again through celite. The titled compound 47 was crystallized from the filtrate as needles. Yield 4.70 g (72%): mp 134-136° C.; 1H NMR (CDCl3) δ 1.28 (t, 3H, CH3), 1.37 (t, 3H, CH3), 4.28-4.40 (m, 4H, 2 CH2), 4.65-4.88 (m, 3H, C4'H and C5'H), 5.85 (m, 2H, C2'H and C3,h), 6.68 (d, 1H, C H, J1',2' =3.90 Hz) and 7.26-8.08 (m, 16H, C2H and PhH). was heated The reaction mixture was evaporated to dryness to remove last traces of hexamethyldisilazine The solid that obtained was dried in vacuo for 6 h The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam filtered through celite to remove tin salts After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol filtered again through celite The titled compound 47 was crystallized from the filtrate as needles

Conditions: temp:135.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 6-methyluracil (2.52 g, 20.0 mmol), hexamethyldisilazine (50 mL) and ammonium sulfate (100 mg ) were refluxed at 135° C. for 6 h. The solvent was removed in vacuo and the residue that obtained was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid thus obtained was dried under vacuum for 6 h. A solution of the 2,4-bis(trimethylsilyloxy)-6-methylpyrimidine (20.0 mmol) in dry acetonitrile (100 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (10.12 g, 20 mmol) and trimethylsilyltriflate (5.78 g, 26.0 mmol). The reaction mixture was stirred under argon at room temperature for 16 h. The reaction mixture was concentrated in vacuo and the residue was dissolved in dichloromethane (200 mL). The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. Further separation of the crude product by silica gel flash column chromatography using the CH2Cl2 →EtOAc as the eluent gave two products. Yield of the 2nd fraction 4.50 g (42%). 1H NMR (CDCl3) δ 2.28 (s, 3H, CH3), 4.65-4.81 (m, 3H, C4'H and C5'H), 5.60 (m, 1H, C3'H), 5.72 (s, 1H), 6.11 (m, 1H), 7.24-8.06 (m, 16H, PhH) and 9.40 (br s, 1H, NH). The first fraction (4.20 g) did not correspond to the desired compound according to 1H NMR. The solvent was removed in vacuo the residue that obtained to remove last traces of hexamethyldisilazine The solid thus obtained was dried under vacuum for 6 h The reaction mixture was concentrated in vacuo the residue was dissolved in dichloromethane (200 mL) The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam Further separation of the crude product by silica gel flash column chromatography gave two products

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a mixture of hexamethyldisilazane (50 mL, 239.77 mmol) and chlorotrimethylsilane (1.0 mL, 21.43 mmol) was added pyridine-4-one-3-carboxamide (1.38 g, 10.0 mmol) (Prepared by the procedure reported: W. C. J. Ross, J. Chem. Soc., C, 1816, (1966); W. Herz and D. R. K. Murty, J. Org. Chem., 26, 122, 1961). The mixture was refluxed with stirring for 2 h and then evaporated to dryness under vacuum and further dried under high vacuum for 2 h at 60° C. The dry gummy residue was suspended in freshly distilled 1.2-dichlorethane (50 mL) and to this suspension was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (5.06 g, 10.0 mmol) and freshly distilled SnCl4 (1.0 mL, 8.52 mmol). The reaction mixture was refluxed for 1.5 h, cooled and diluted with CH2Cl2 (100 mL) and sat. aqueous NaHCO3 (25 mL). The mixture was filtered through celite and the bed was washed with CH2Cl2 (20 mL). The organic phase was separated, washed with water until the washings are neutral, dried over anhydrous sodium sulfate. The organic extract was evaporated to dryness to give a gummy residue. The residue was purified by flash chromatography over silica gel using CH2Cl2 →EtOAc as the eluent. Pure fractions were pooled and concentrated to provide 0.50 g (9%) of 33 as white foam: 1H NMR (CDCl3): δ 4.94 (m, 3H, C4'H and C5'H), 6.12 (m, 1H), 6.20 (m, 1H), 6.32 (d, 1H) and 7.20-8.30 (m, 20H). Prepared by the procedure The mixture was refluxed evaporated to dryness under vacuum further dried under high vacuum for 2 h at 60° C The reaction mixture was refluxed for 1.5 h cooled The mixture was filtered through celite the bed was washed with CH2Cl2 (20 mL) The organic phase was separated washed with water until the washings dried over anhydrous sodium sulfate The organic extract was evaporated to dryness to give a gummy residue The residue was purified by flash chromatography over silica gel concentrated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of diethyl imidazole-4,5-dicarboxylate (2.65 g, 12.50 mmol) and ammonium sulfate (50 mg) was heated at reflux at 135° C. for 6 h with hexamethyldisilazine (50 mL). The reaction mixture was evaporated to dryness and the residue was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid that obtained was dried in vacuo for 6 h and used for the next step without further characterization. To a solution of the above residue (12.5 mmol) in 1,2-dichlorethane (60 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (5.06 g, 10 mmol) and tin tetrachloride (1.68 mL, 14.16 mmol) at 10° C. The reaction mixture was stirred under the atmosphere of argon at room temperature for 6 h. The reaction was checked by TLC using hexane and ethyl acetate (7:3). TLC indicated no starting material remained. The reaction mixture was diluted with dichloromethane (200 mL). The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. The residue was dissolved in dichloromethane (100 mL) and filtered through celite to remove tin salts. After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol and filtered again through celite. The titled compound 47 was crystallized form the filtrate as needles. Yield 4.70 g (72%): mp 134-136° C.; 1H NMR (CDCl4) δ1.28 (t, 3H, CH3), 1.37 (t, 3H, CH3), 4.28-4.40 (m, 4H, 2CH2), 4.65-4.88 (m, 3H, C4′H and C5,H), 5.85 (m, 2H, C2′H and C3′H), 6.68 (d, 1H, C1′H, J1′,2′=3.90 Hz) and 7.26-8.08 (m, 16H, C2H and PhH). was heated The reaction mixture was evaporated to dryness to remove last traces of hexamethyldisilazine The solid that obtained was dried in vacuo for 6 h The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam filtered through celite to remove tin salts After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol filtered again through celite The titled compound 47 was crystallized form the filtrate as needles

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of diethyl imidazole-4,5-dicarboxylate (2.65 g, 12.50 mmol) and ammonium sulfate (50 mg) was heated at reflux at 135° C. for 6 h with hexamethyldisilazine (50 mL). The reaction mixture was evaporated to dryness and the residue was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid that obtained was dried in vacuo for 6 h and used for the next step without further characterization. To a solution of the above residue (12.5 mmol) in 1,2-dichlorethane (60 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (5.06 g, 10 mmol) and tin tetrachloride (1.68 mL, 14.16 mmol) at 10° C. The reaction mixture was stirred under the atmosphere of argon at room temperature for 6 h. The reaction was checked by TLC using hexane and ethyl acetate (7:3). TLC indicated no starting material remained. The reaction mixture was diluted with dichloromethane (200 mL). The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. The residue was dissolved in dichloromethane (100 mL) and filtered through celite to remove tin salts. After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol and filtered again through celite. The titled compound 47 was crystallized form the filtrate as needles. Yield 4.70 g (72%): mp 134-136° C.; 1H NMR (CDCl4) δ1.28 (t, 3H, CH3), 1.37 (t, 3H, CH3), 4.28-4.40 (m, 4H, 2CH2), 4.65-4.88 (m, 3H, C4′H and C5,H), 5.85 (m, 2H, C2′H and C3′H), 6.68 (d, 1H, C1′H, J1′,2′=3.90 Hz) and 7.26-8.08 (m, 16H, C2H and PhH). was heated The reaction mixture was evaporated to dryness to remove last traces of hexamethyldisilazine The solid that obtained was dried in vacuo for 6 h The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam filtered through celite to remove tin salts After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol filtered again through celite The titled compound 47 was crystallized form the filtrate as needles

Conditions: temp:135.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 6-methyluracil (2.52 g, 20.0 mmol), hexamethyldisilazine (50 mL) and ammonium sulfate (100 mg ) were refluxed at 135° C. for 6 h. The solvent was removed in vacuo and the residue that obtained was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid thus obtained was dried under vacuum for 6 h. A solution of the 2,4-bis(trimethylsilyloxy)-6-methylpyrimidine (20.0 mmol) in dry acetonitrile (100 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (10.12 g, 20 mmol) and trimethylsilyltriflate (5.78 g, 26.0 mmol. The reaction mixture was stirred under argon at room temperature for 16 h. The reaction mixture was concentrated in vacuo and the residue was dissolved in dichloromethane (200 mL). The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. Further separation of the crude product by silica gel flash column chromatography using the CH2Cl2→EtOAc as the eluent gave two products. Yield of the 2nd fraction 4.50 g (42%). 1H NMR (CDCl3) δ2.28 (s, 3H, CH3), 4.65-4.81 (m, 3H, C4′H and C5′H), 5.60 (m, 1H, C3′H), 5.72 (s, 1H), 6.11 (m, 1H), 7.24-8.06 (m, 16H, PhH) and 9.40 (br s, 1H, NH). The first fraction (4.20 g) did not correspond to the desired compound according to 1H NMR. The solvent was removed in vacuo the residue that obtained to remove last traces of hexamethyldisilazine The solid thus obtained was dried under vacuum for 6 h The reaction mixture was concentrated in vacuo the residue was dissolved in dichloromethane (200 mL) The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam Further separation of the crude product by silica gel flash column chromatography gave two products

Conditions: temp:135.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 6-methyluracil (2.52 g, 20.0 mmol), hexamethyldisilazine (50 mL) and ammonium sulfate (100 mg ) were refluxed at 135° C. for 6 h. The solvent was removed in vacuo and the residue that obtained was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid thus obtained was dried under vacuum for 6 h. A solution of the 2,4-bis(trimethylsilyloxy)-6-methylpyrimidine (20.0 mmol) in dry acetonitrile (100 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (10.12 g, 20 mmol) and trimethylsilyltriflate (5.78 g, 26.0 mmol. The reaction mixture was stirred under argon at room temperature for 16 h. The reaction mixture was concentrated in vacuo and the residue was dissolved in dichloromethane (200 mL). The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. Further separation of the crude product by silica gel flash column chromatography using the CH2Cl2→EtOAc as the eluent gave two products. Yield of the 2nd fraction 4.50 g (42%). 1H NMR (CDCl3) δ2.28 (s, 3H, CH3), 4.65-4.81 (m, 3H, C4′H and C5′H), 5.60 (m, 1H, C3′H), 5.72 (s, 1H), 6.11 (m, 1H), 7.24-8.06 (m, 16H, PhH) and 9.40 (br s, 1H, NH). The first fraction (4.20 g) did not correspond to the desired compound according to 1H NMR. The solvent was removed in vacuo the residue that obtained to remove last traces of hexamethyldisilazine The solid thus obtained was dried under vacuum for 6 h The reaction mixture was concentrated in vacuo the residue was dissolved in dichloromethane (200 mL) The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam Further separation of the crude product by silica gel flash column chromatography gave two products

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of diethyl imidazole-4,5-dicarboxylate (2.65 g, 12.50 mmol) and ammonium sulfate (50 mg) was heated at reflux at 135° C. for 6 h with hexamethyldisilazine (50 mL). The reaction mixture was evaporated to dryness and the residue was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid that obtained was dried in vacuo for 6 h and used for the next step without further characterization. To a solution of the above residue (12.5 mmol) in 1,2-dichlorethane (60 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (5.06 g, 10 mmol) and tin tetrachloride (1.68 mL, 14.16 mmol) at 10° C. The reaction mixture was stirred under the atmosphere of argon at room temperature for 6 h. The reaction was checked by TLC using hexane and ethyl acetate (7:3). TLC indicated no starting material remained. The reaction mixture was diluted with dichloromethane (200 mL). The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. The residue was dissolved in dichloromethane (100 mL) and filtered through celite to remove tin salts. After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol and filtered again through celite. The titled compound 47 was crystallized from the filtrate as needles. Yield 4.70 g (72%): mp 134-136° C.; 1H NMR (CDCl3) δ 1.28 (t, 3H, CH3), 1.37 (t, 3H, CH3), 4.28-4.40 (m, 4H, 2 CH2), 4.65-4.88 (m, 3H, C4'H and C5'H), 5.85 (m, 2H, C2'H and C3,h), 6.68 (d, 1H, C H, J1',2' =3.90 Hz) and 7.26-8.08 (m, 16H, C2H and PhH). was heated The reaction mixture was evaporated to dryness to remove last traces of hexamethyldisilazine The solid that obtained was dried in vacuo for 6 h The organic layer was washed with cold sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam filtered through celite to remove tin salts After evaporation in vacuo the residue (4.70 g) was dissolved in ethanol filtered again through celite The titled compound 47 was crystallized from the filtrate as needles

Conditions: temp:135.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 6-methyluracil (2.52 g, 20.0 mmol), hexamethyldisilazine (50 mL) and ammonium sulfate (100 mg ) were refluxed at 135° C. for 6 h. The solvent was removed in vacuo and the residue that obtained was co-evaporated twice with dry toluene (2×50 mL) to remove last traces of hexamethyldisilazine. The solid thus obtained was dried under vacuum for 6 h. A solution of the 2,4-bis(trimethylsilyloxy)-6-methylpyrimidine (20.0 mmol) in dry acetonitrile (100 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (10.12 g, 20 mmol) and trimethylsilyltriflate (5.78 g, 26.0 mmol). The reaction mixture was stirred under argon at room temperature for 16 h. The reaction mixture was concentrated in vacuo and the residue was dissolved in dichloromethane (200 mL). The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL), dried over sodium sulfate and concentrated to yield a white foam. Further separation of the crude product by silica gel flash column chromatography using the CH2Cl2 →EtOAc as the eluent gave two products. Yield of the 2nd fraction 4.50 g (42%). 1H NMR (CDCl3) δ 2.28 (s, 3H, CH3), 4.65-4.81 (m, 3H, C4'H and C5'H), 5.60 (m, 1H, C3'H), 5.72 (s, 1H), 6.11 (m, 1H), 7.24-8.06 (m, 16H, PhH) and 9.40 (br s, 1H, NH). The first fraction (4.20 g) did not correspond to the desired compound according to 1H NMR. The solvent was removed in vacuo the residue that obtained to remove last traces of hexamethyldisilazine The solid thus obtained was dried under vacuum for 6 h The reaction mixture was concentrated in vacuo the residue was dissolved in dichloromethane (200 mL) The organic layer was washed with sat. sodium bicarbonate (200 mL) and brine (100 mL) dried over sodium sulfate concentrated to yield a white foam Further separation of the crude product by silica gel flash column chromatography gave two products

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a mixture of hexamethyldisilazane (50 mL, 239.77 mmol) and chlorotrimethylsilane (1.0 mL, 21.43 mmol) was added pyridine-4-one-3-carboxamide (1.38 g, 10.0 mmol) (Prepared by the procedure reported: W. C. J. Ross, J. Chem. Soc., C, 1816, (1966); W. Herz and D. R. K. Murty, J. Org. Chem., 26, 122, 1961). The mixture was refluxed with stirring for 2 h and then evaporated to dryness under vacuum and further dried under high vacuum for 2 h at 60° C. The dry gummy residue was suspended in freshly distilled 1.2-dichlorethane (50 mL) and to this suspension was added 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose (5.06 g, 10.0 mmol) and freshly distilled SnCl4 (1.0 mL, 8.52 mmol). The reaction mixture was refluxed for 1.5 h, cooled and diluted with CH2Cl2 (100 mL) and sat. aqueous NaHCO3 (25 mL). The mixture was filtered through celite and the bed was washed with CH2Cl2 (20 mL). The organic phase was separated, washed with water until the washings are neutral, dried over anhydrous sodium sulfate. The organic extract was evaporated to dryness to give a gummy residue. The residue was purified by flash chromatography over silica gel using CH2Cl2 →EtOAc as the eluent. Pure fractions were pooled and concentrated to provide 0.50 g (9%) of 33 as white foam: 1H NMR (CDCl3): δ 4.94 (m, 3H, C4'H and C5'H), 6.12 (m, 1H), 6.20 (m, 1H), 6.32 (d, 1H) and 7.20-8.30 (m, 20H). Prepared by the procedure The mixture was refluxed evaporated to dryness under vacuum further dried under high vacuum for 2 h at 60° C The reaction mixture was refluxed for 1.5 h cooled The mixture was filtered through celite the bed was washed with CH2Cl2 (20 mL) The organic phase was separated washed with water until the washings dried over anhydrous sodium sulfate The organic extract was evaporated to dryness to give a gummy residue The residue was purified by flash chromatography over silica gel concentrated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 5.37 g of crude 2,3,5-tri-O-benzoyl-1-O-methyl-L-ribofuranose synthesized from L-ribose (1.0 g; 6.66 mmol) in accordance with the method described in Helvetica Chimica Acta 1959, (121), 1171-1173p was added to a 100-ml flask. Thereafter, acetic anhydride (3.73 ml; 5.95 equivalents) and acetic acid (1.60 ml; 2.80 equivalents) were added thereto. The obtained mixture was cooled on ice, and thereafter, concentrated sulfuric acid (530 μl; 1.5 equivalents) was slowly added dropwise thereto. After completion of the reaction for 30 minutes, cold water (50 ml) was slowly added dropwise to the reaction solution, and an upper aqueous layer was separated. The precipitated semi-oily solid was dried under reduced pressure. Thus, 3.97 g of crude 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose was obtained in the form of a light yellow oily solid. The obtained solid was analyzed by HPLC. As a result, the ratio of α-/β-anomers in the crude 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose was 35/65, and the reaction yield of the β-anomer from the total 3 steps was 56%. was added to a 100-ml flask The obtained mixture was cooled on ice After completion of the reaction for 30 minutes an upper aqueous layer was separated The precipitated semi-oily solid was dried under reduced pressure

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 59.40 g out of 62.69 g of the crude 2,3,5-tri-O-benzoyl-1-O-methyl-L-ribofuranose synthesized in (2) above was added to a 1-L flask. Thereafter, acetic anhydride (31.2 ml; 2.65 equivalents), acetic acid (26.7 ml; 3.73 equivalents), and pyridine (7.1 ml; 0.8 equivalents) were added to the flask. The obtained mixture was cooled to an ice-cooled temperature, and thereafter, concentrated sulfuric acid (13.5 ml; 2.03 equivalents) was slowly added dropwise thereto. After completion of the reaction for 30 minutes, cold water (200 ml) was slowly added dropwise to the reaction product, and crystals were then filtrated. The obtained solid was dried. Thus, 69.83 g of crude 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose was obtained in the form of a light yellow solid. The obtained compound was analyzed by HPLC. As a result, the ratio of α-/β-anomers in the 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose was 4/96, and the reaction yield of the β-anomer from the total 3 steps was 84%. 69.83 g of the crude 1-O-acetyl-2,3,5-tri-O-benzoyl-L-ribofuranose was suspended in isopropyl alcohol (92 ml), and the suspension was then heated to reflux for 1 hour. Thereafter, the reaction solution, in which the aforementioned compound had been completely dissolved, was cooled to an ice-cooled temperature, and it was then stirred for 30 minutes. Thereafter, the resultant mixture was filtrated, and the obtained crystals were then dried under reduced pressure. Thus, 1-O-acetyl-2,3,5-tri-O-benzoyl-β-L-ribofuranose was obtained from L-ribofuranose in the form of white crystals with a purity of 99% or more at a total yield of 75%. the suspension was then heated to reflux for 1 hour Thereafter, the reaction solution, in which the aforementioned compound had been completely dissolved cooled temperature, and it Thereafter, the resultant mixture was filtrated the obtained crystals were then dried under reduced pressure