To a stirred mixture of 13.5 mL (4.09 mmol) of a 0.303 N standard solution of silylated N-acetylguanine in 1,2-dichloroethane and 1.86 g (3.7 mmol) of benzoate-protected 1-acetoxy ribose in 35 mL of 1,2-dichloroethane was added 6.32 mL (4.46 mmol) of a 0.705 N standard solution of TMSOTf in 1,2-dichloroethane. The reaction mixture was heated at reflux for 1.5–4 hours, and then diluted with CHCl. On workup with ice-cold NaHCO solution, there was obtained 2.32 g of crude product, which was kept for 42 hours in 125 mL of methanolic ammonia at 24°. After workup, recrystallization from HO gave, in two crops, 0.69 g (66%) of pure guanosine, which was homogeneous (R 0.3) in the partition system n-butanol:acetic acid:HO (5:1:4) and whose H NMR spectrum at 400 MHz in DO showed only traces of the undesired N-anomer of guanosine. H NMR (CDCl): δ 3.55, 3.63, 3.90, 4.11, 4.43, 5.10, 5.20, 5.45, 5.72, 6.52, 7.97, 10.75.