Hydrazine hydrate (1:1) → 9-(3,5-Di-O-benzoyl-beta-L-xylofuranosyl)adenine

A solution of 9-(2-O-acetyl-3,5-di-O-benzoyl-β-L-xylofuranosyl)adenine 2 [Ref.: Gosselin, G.; Bergogne, M. -C.; Imbach, J. -L., “Synthesis and Antiviral Evaluation of β-L-Xylofuranosyl Nucleosides of the Five Naturally Occuring Nucleic Acid Bases”, Journal of Heterocyclic Chemistry, 1993, 30 (October-November), 1229-1233] (8.30 g, 16.05 mmol) and hydrazine hydrate 98% (234 mL, 48.5 inmol) in a mixture of pyridine/glacial acetic acid (4/1, v/v, 170 mL) was stirred at room temperature for 22 h. The reaction was quenched by adding acetone (40 mL) and stirring was continued for one additional hour. The reaction mixture was reduced to one half of its volume, diluted with water (250 mL) and extracted with chloroform (2×150 mL). The organic layer was washed successively with an aqueous saturated solution of NaHCO3 (3×100 mL) and water (3×100 mL), dried, filtered, concentrated and co-evaporated with toluene and methanol. The residue was purified by silica gel column chromatography (0-3% MeOH in dichloromethane) to give 3 (5.2 g, 68%) precipitated from diisopropylic ether: 1H NMR (DMSO-d6): δ 4.5-4.9 (m, 4H, H-2′, H-4′, H-5′ and H-5″), 5.64 (t, 1H, H-3′, J2′,3′=J3′,4′=3.5 Hz), 6.3 (br s, 1H, OH-2′), 6.45 (d, 1H, H-1′, J1′,2′=4.6 Hz), 7.3 (br s, 2H, NH2-6), 7.4-7.9 (m, 10H, 2 benzoyls), 8.07 and 8.34 (2s, 2H, H-2 and H-8); ms: matrix G/T, (FAB+) m/z 476 [M+H]+, 136 [BH2]+, (FAB−) m/z 474 [M−H]−, 134 [B]−; UV (95% ethanol): λmax 257 nm (ε 16400), 230 nm (ε 29300), λmax 246 nm (ε 14800); [α]D20=−64 (c 1.07, CHCl3). Anal. Calcd for C24H21N5O4 (M=475.45): C, 60.43; H, 4.45; N, 14.73. Found: C, 60.41; H, 4.68; N, 14.27.