To the stirring solution of (R)-7,8-dihydro-3-(5-hydroxyhexyl)-1-methyl-1H-imidazo[2,1-f]-purine-2,4(3H,6H)-dione (CT-13430) (200 mg, 0.65 mmol) and imidazole (68 mg, 1.0 mmol) in dimethylformamide (1 ml) was added tert-butyldimethylsilyl chloride (127 mg, 1.30 mmol). After stirred at room temperature for 16 hours, the reaction mixture was treated with water and extracted with ethyl acetate (2×15 ml). The combined extracts were washed with water (2×5 ml), with saturated aqueous sodium chloride solution (5 ml), and dried over magnesium sulfate. Concentrating under reduced pressure to provide (R)-7,8-dihydro-1-methyl-3-(5-tert-butyldimethylsilyloxyhexyl)-1H-imidazo[2,1-f]-purine-2,4(3H, 6H)-dione (280 mg, 100% yield) as a white powder.
