Pyridine → 7-(2-Thienyl)-3-[2-deoxy-5-O-(4,4'-dimethoxytrityl)-beta-D-ribofuranosyl]-3H-imidazo[4,5-b]pyridine 2-cyanoethyl-N,N-diisopropylphosphoramidite

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Reaction Steps

Compound 7 (425 mg, 0.69 mmol) was azeotroped three times with anhydrous pyridine and then three times with anhydrous acetonitrile. This was dissolved in anhydrous acetonitrile (4.6 ml), followed by addition of 2-cyanoethyl tetraisopropylphosphorodiamidite (262 μl, 0.82 mmol)) and a 0.45 M acetonitrile solution of tetrazole (1.68 ml). This mixture was stirred for 1 hour at room temperature. After addition of anhydrous methanol (90 μl), the mixture was poured into water (50 ml) and extracted with 1% triethylamine (v/v)-containing methylene chloride (50 ml×3). After drying over Na2SO4, the solvent was distilled off under reduced pressure. The residue was purified by flash silica gel chromatography using 2% triethylamine (v/v)-containing hexane:ethyl acetate (4:1 to 3:2) as an elution solvent to give 490 mg of Compound 8 in a yield of 87%.

Provenance & Evidence