反应详情

A 100-ml four-necked flask was subjected to nitrogen substitution. 11.32 g (corresponding to 40 mmol of L-ribose) of the 2,3,5-tri-O-acetyl-1-O-methyl-L-ribofuranose obtained in Example B1(1) and 20 ml of diisopropyl ether were added to the flask. The flask was maintained at a temperature of 0±5° C. in an ice bath, and 8.17 g (2.0 equivalents) of acetic anhydride was added thereto. While stirring in an ice bath, 3.2 g (0.8 equivalents) of concentrated sulfuric acid was added dropwise thereto at an internal temperature of 0±5° C. The mixture was stirred in an ice bath for 3.5 hours, and the reaction product was then maintained at 5° C. or lower in a refrigerator overnight. While stirring in an ice bath, 7.87 g of sodium acetate was added to the reaction product, and the obtained mixture was then stirred in an ice bath for 30 minutes. 120 ml of ethyl acetate and a saturated sodium bicarbonate aqueous solution were added to the reaction solution at room temperature until the aqueous layer was neutralized, followed by liquid separation. The aqueous layer was extracted with 120 ml of ethyl acetate, and organic layers were gathered. The gathered layers were washed with 120 ml of a saturated sodium bicarbonate aqueous solution and then with 120 ml of a saturated sodium chloride aqueous solution 2 times. The organic layer was dried over anhydrous sodium sulfate, and the drying agent was then removed by filtration, concentrated under reduced pressure. Thus, 16.10 g of crude 1,2,3,5-tetra-O-acetyl-L-ribofuranose was obtained in the form of yellow oil. The obtained compound was analyzed by HPLC. As a result, it was found that the crude product contained 9.76 g of 1,2,3,5-tetra-O-acetyl-L-ribofuranose, that the ratio of α-/β-anomers was 7/93, and that the total reaction yield of the β-anomer from L-ribose was 72%.