31.18 g of the crude 1-O-methyl-L-ribofuranose synthesized in (1) above, toluene (175 ml), a 25 wt. % sodium hydroxide aqueous solution (111 ml), and tetra-normal-butyl ammonium bromide (1.20 g; 5 molar % ratio) were added to a 1-L flask. The obtained mixture was cooled to an ice-cooled temperature, and benzoyl chloride (56.6 mol; 3.05 equivalents) was then slowly added dropwise thereto. The temperature was increased to room temperature, and the reaction was then carried out for 2 hours. The reaction product was again cooled to an ice-cooled temperature, and it was then diluted with toluene (200 ml) and a 1 N sodium hydroxide aqueous solution (100 ml). The temperature was increased to room temperature, and an organic layer was separated from an aqueous layer. The organic layer was washed with a 1 N sodium hydroxide aqueous solution (100 ml) 2 times, and was then washed with a 3 N hydrochloric acid aqueous solution (200 ml), so that the organic layer was concentrated. Thus, 62.69 g of crude 2,3,5-tri-O-benzoyl-1-O-methyl-L-ribofuranose was obtained in the form of a colorless oily liquid.
