1,2,3,5-Tetraacetyl-beta-D-ribofuranose → 2-Amino-5,6-dichloro-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)benzimidazole

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Reaction Conditions

Reaction Steps

2-Amino-5,6-dichlorobenzimidazole (4) (3 g, 16 mmole) was dissolved in dry acetonitrile (150 ml) and stirred in an inert atmosphere at 60° C. BSA (4.37 ml, 17 mmole) was added and the mixture was stirred for 10 minutes. 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose (5.09 g, 16 mmole) and TMSTf (3.29 ml, 17 mmole) were added to the clear solution and the mixture was allowed to stir at 60° C. for 1 hr. The mixture was concentrated under reduced pressure and separated on a silica column to yield 1.14 g (15%) of 2-amino-5,6-dichloro-1-(2,3,5,tri-O-acetyl-β-D-ribofuranosyl) benzimidazole (43). 13C NMR (CDCl3): d 170.04 ppm, 169.56, 169.11, 154.57, 141.64, 132.53, 125.90, 1123.45, 117.72, 109.49, 85.78, 80.99, 70.95, 69.83, 62.91, 20.74, 20.54, 20.20. 1H NMR (CDCl3): d 0.96 ppm (s, 3H), 1.09 (s, 3H), 1.13 (s, 3H), 3.75 (m, 2H), 4.08 (dd, 1H), 5.00 (dd, 1H), 5.13 (t, 1H), 5.42 (s, 2H), 5.61 (d, 1H), 7.27 (s, 1H), 7.42 (s, 1H). MS (FAB) m/e 758,718, 676, 460, 426, 259, 217, 139.

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