[NH:1]1[C:12](=[O:13])[C:11]2[N:9]([CH3:10])[CH:8]=[N:7][C:6]=2[N:4]([CH3:5])[C:2]1=[O:3].[H-].[Na+].CS(O[CH2:21][CH2:22][CH2:23][CH:24]=[CH:25][CH3:26])(=O)=O.O>CS(C)=O>[CH2:26]([N:1]1[C:12](=[O:13])[C:11]2[N:9]([CH3:10])[CH:8]=[N:7][C:6]=2[N:4]([CH3:5])[C:2]1=[O:3])[CH2:25][CH2:24][CH:23]=[CH:22][CH3:21]A mixture of theobromine (2.16 g, 12 mmol) and sodium hydride (288 mg, 12 mequivalents) in dimethylsufoxide (10 mL) was stirred for 30 minutes and then a solution of 1-methansulfonyloxy-4-hexene in dimethylsulfoxide (10 mL) was added. After 84 hours of stirring, water (70 mL) is added and the mixture extracted with ether (3×50 mL). The combined extracts were washed with water (50 mL) and dried over magnesium sulfate. The solvent was then evaporated under vacuum. The residue was purified by flash chromatography (22 g silica gel using an ethyl acetate eluant, 500 mL), yielding 2.1 g (67%) 1-(4-hexenyl)-3,7-dimethylxanthine. To a solution of 1-(4-hexenyl)-3,7-dimethylxanthine (270 mg, 1.03 mmol) in dichloromethane (10 mL) was added saturated aqueous sodium bicarbonate solution (10 mL), followed by a solution of 50-60% 3-chloroperoxybenzoic acid (889 mg, 2.58 mmol) in dichloromethane (5 mL) over 1 minute. After 20 hours of stirring, 20% aqueous sodium metabisulfite solution (15 mL) was added over 1 minute. The mixture was then extracted with dichloromethane (3×15 mL). The combined extracts were washed with saturated aqueous sodium bicarbonate solution (3×20 mL) and dried over magnesium sulfate. The sovent was evaporated under vacuum. The residue was purified by flash chromatography using 14 g of silica gel and eluting with ethyl acetate (100 ml) followed by 8% methanol-dichloromethane (60 mL), yielding 80 mg (28% yield) of 1-(4,5-oxohexyl)-3,7-dimethylxanthine as a white powder.
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