[OH-].[Na+].[CH3:3][N:4]1[C:12]2[N:11]=[C:10]([CH3:13])[NH:9][C:8]=2[C:7](=[O:14])[NH:6][C:5]1=[O:15].[CH2:16](Br)[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1>O.CO>[CH2:16]([N:9]1[C:8]2[C:7](=[O:14])[NH:6][C:5](=[O:15])[N:4]([CH3:3])[C:12]=2[N:11]=[C:10]1[CH3:13])[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1A solution of sodium hydroxide (400 mg) in water (5 ml) was added to a suspension of 3,8-dimethylxanthine (1.80 g) in methanol (10 ml) at 70° C. and stirred for 1 hour. Benzyl bromide (1.2 ml) was added and the mixture was stirred at 70-80° C. for 5 hours. After evaporation of the solvent under reduced pressure, the residue was suspended in saturated aqueous ammonium chloride solution (50 ml) and extracted with ethyl acetate (3×75 ml). The combined extracts were washed with saturated aqueous sodium chloride solution (30 ml), dried over magnesium sulfate and concentrate. The product was purified by recrystallization from ethanol. Yield=1.06 g.
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