Thymidine → 5'-O-(4,4'-Dimethoxytrityl)thymidine

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Reaction Steps

In a 250-ml three-necked flask, thymidine and dimethoxytrityl chloride in anhydrous pyridine are introduced in succession under inert gas and stirred for 2 hours at room temperature. The TLC control test of the reaction (V(MeOH):V(CH2Cl2)=1:19) shows the 5′-O-protected compound (Rf=0.26) to be the main product. It also contains one faint spot each for the starting material (Rf=0.00) and the doubly protected byproduct, 3′,5′-bis-O-(4,4′-dimethoxytrityl)thymidine (Rf=0.71). The reaction solution is then decanted slowly into 1.5 l of vigorously stirred ice water. After 30 minutes of stirring, the yellow suspension is suction-filtered, and the residual moisture is removed from the solid in the rotary evaporator by azeotropic distillation two times with ethanol. Alternatively, the raw product is recrystallized from a benzene-acetone mixture or is purified by means of column chromatography (silica gel 60; Ø=6 cm; h=45 cm; V(MeOH):V(CH2Cl2)=1:19+0.1% of triethylamine; absorbed on about 20 g of silica gel 60). After drying in high vacuum, it yields the product, 5′-O-(4,4′-dimethoxytrityl)thymidine.

Provenance & Evidence