Hexamethyldisilazane → 2-Amino-8-(2,3,5-tri-O-benzoyl-beta-D-ribofuranosyl)imidazo[1,2-a]-s-triazin-4-one

Participants

Reaction Steps

A mixture of dry 2-aminoimidazo[1,2-a]-s-triazin-4-one (V) 3.02 g, 0.020 mol), freshly distilled hexamethyldisilazane (15.0 mL), and a few crystals of ammonium sulfate (25 mg) was heated at reflux temperature for 15 h. with the exclusion of moisture. The clear, slightly brown solution was fractionated by distillation to remove excess of hexamethyldisilazane and the residual gum was presumed to be the bis(trimethylsilyl) derivative which was used without further prification. To a solution of the above trimethylsilyl derivative in anhydrous 1,2-dichloroethane (100 mL) was added 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (10.09 g, 0.02 mol) followed by stannic chloride (7.0 g, 0.027 mol). The reaction mixture was protected from moisture and stirred for 30 h. at ambient temperature. The brown reaction solution was then poured into 200 mL of chloroform, with efficient stirring and keeping the mixture basic at all times. The resulting emulsion was filtered through a Celite pad which was washed with chloroform (3×25 mL). The combined organic layer was washed with water (2×100 mL) before it was dried over anhydrous sodium sulfate. The solvent was evaporated to a light brown foam which was chromatographed on an open-bed, silica gel column (5×75 cm) prepacked in ethyl acetate and eluted with ethyl acetate-water-1-propanol (4:2:1, v/v, upper phase). The band containing the requisite product was collected and the solvent evaporated to leave 6.8 g (56.30%) of a light yellow, chromatographically homogeneous foam: [α]25D -32.0° (cl.O.Me2SO); UVλmax (pH 1) 233 nm (ε=45800), 268 (18800); UVλmax (pH 7) 235 nm (ε=39400), 263 sh (24700); UVλmax (pH 11) 234 nm (ε=42300), 260 sh (20600). Anal. (C31H25N5O8.0.5H2O, 604.57) C, H, N.

Provenance & Evidence