The potential antiviral, antibacterial, and antitumorous activities shown by C-nucleosides which have the carbon-carbon glycosidic bond have incited many attempts at the organic synthesis. 2,3,5-Tri-O-benzoyl-β-D-ribofuranosyl cyanide (2) has been used as a potentially versatile intermediate for the synthesis of C-nucleoside derivatives. Ribofuranosyl cyanide 2 was prepared primarily from the reaction of 1-halo2,3,5-tri-O-benzoyl-β-D-ribofuranose which was prepared from the reaction of 1-O-acetyl-2,3,5-tri-O-benzoyl-β-Dribofuranose (1) with mercuric cyanide. An efficient procedure for the synthesis of 2 was accomplished by the reaction of 1-O-acetate ribose 1 with cyanotrimethylsilane by Utimoto and Horiie. Our synthetic approach was to prepare 2,3,5-tri-O-benzoyl-β-D-ribofuranosyl cyanide (3) from the reaction of 1-O-acetyl-2,3,5-tri-O-benzoylβ-D-ribofuranose (1) with potassium cyanide instead of TMSCN (Scheme 1) because potassium cyanide is cheaper and more easily commercially available than TMS-CN. Potassium cyanide could provide the cyanide ion in the presence of 18-crown-6 in nonpolar solvent, which is called phase transfer reaction. After 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (1) was dissolved in dry methylene chloride, stannic chloride, 18-crown-6, and potassium cyanide were added to the solution and then the reaction mixture was heated under reflux for 24 h. Ribofuranose 1 was converted to 2,3,5-tri-O-benzoyl-β-D-ribofuranosyl cyanide (3) via 1,2-acyloxonium intermediate 2 which allowed a naked cyanide ion to attact on the β-face. From the H NMR spectrum of the obtained product 3, the anomeric proton at C1 was identified as a doublet at δ = 5.49 ppm (J12 = 4.0 Hz). For an adequate choice of reagent ratio, several reactions were carried out. The optimized condition was obtained from the reaction with a molar ratio of compound 1/KCN/stannic chloride/18-crown-6 = 1.0 : 2.0 : 1.5 : 0.15. 1,2,3,5-Tetra-O-acetyl-β-D-ribofuranose (4) was also tested under the phase transfer reaction condition to synthesize 2,3,5tri-O-acetyl-β-D-ribofuranosyl cyanide. The reaction of 4 in the similar manner as compound 3 by using stannic chloride as a Lewis acid gave no desired product. On the contrary, the reaction of compound 4 in the presence of BF3·OEt2 provided two different products, 5 and 6, separated by flash silica gel column chromatography (Scheme 2). H NMR spectrum of the isolated product 5 showed two anomeric protons at 5.92 and 5.95 (J12 = 3.9 and 4.2 Hz). The separated product 5, therefore, was expected to be a mixture of 3,5-di-O-acetyl-1,2-O-(1-endo-cyanoethylidene)α-D-ribofuranose and its exo-isomer which could be also obtained from the reaction of 1-O-acetate 4 with TMS-CN in the presence of BF3·OEt2. H NMR spectrum of product 6, identified as a 3,5-di-Oacetyl-1,2-O-(1-endo or exo-acetoxy-ethylidene)-α-D-ribofuranose, presented four methyl groups at the range of δ = 2.02-2.07 ppm and a C1 proton with a doublet at δ = 6.36 (J12 = 4.2 Hz), whereas the starting material 4 showed a C1 proton at δ = 6.09 ppm.