Dimethylformamide → 3,7-Dihydro-6-methylthio-3-n-propyl-2H-purin-2-one

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Reaction Steps

In an argon atmosphere(9.77 g (244 mmol) of 60% sodium hydride was washed with n-hexane 3 times. The solvent was evaporated under reduced pressure and dried. After 900 ml of N,N'-dimethylformamide was added 57.0 g (271 mmol) of 3-n-propyl-6-thioxanthine (Japanese Published Unexamined Patent Application No. 183287/86) was gently added under ice cooling. 15 minutes after, 15.2 ml (244 mmol) of methyl iodide was dropwise added to the reaction mixture. After stirring for 30 minutes, 50 ml of ethanol was added and the mixture was concentrated under reduced pressure. Then 400 ml of water was added and precipitates were collected by filtration to give 13.9 g (yield, 23%) of Compound b as light yellow powder. The filtrate was extracted 5 times with 200 ml of chloroform. After washing with a saturated aqueous sodium chloride solution, the extract was dried over anhydrous sodium sulfate, the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: 10% methanol/chloroform) to give further 16.0 g (yield, 26%) of Compound b as a light yellow powder.

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