1,1'-(Chlorophenylmethylene)bis(4-methoxybenzene) → N2 (phenylacetyl)-5'-O-(4,4'-dimethoxytrityl)-2'-deoxyguanosine

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Reaction Conditions

Reaction Steps

N2 -(Phenylacetyl)-2'-deoxyguanosine (2a) (23.12 g, 60 mmoles) was dried by coevaporation with dry pyridine (2×100 ml), dissolved in 600 ml of dry pyridine and ice cooled. To this solution, 4,4'-dimethoxytrityl chloride (25.5 g, 72 mmoles) was added. The reaction mixture was stirred at 5° C. for 20 hours. After removing the pyridine under reduced pressure, the resulting residue was taken up in 600 ml of methylene chloride, washed successively with 2×400 ml of 5% NaHCO3 and 1×400 ml of water. The organic layer was dried over anhydrous sodium sulfate and concentrated to near dryness. The product was purified on a silica gel column (6×50 cm) by gradient elution with 1L 0-6% methylene chloride-methanol. The desired fractions were collected, concentrated to about 100 ml and added dropwise to 1.5L cooled hexane (0° C.) to precipitate the product. The precipitated product was filtered, washed with hexane and air dried to yield 24 g (58%) of tritylated product (3a), as confirmed by spectroscopic and elemental analysis.

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