Boron trifluoride etherate → 1-(5-Aminohexyl)-3,7-dimethylxanthine

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Reaction Steps

The method described in Koziara and Zwierzak, Tetrahedron Letters 28:6513-6516,1987 was followed to make CT1520. Briefly, boron trifluoride etherate (0.06 mol) was added dropwise at 10°-30° C. to a stirred solution of 1-(5-hydroxyhexyl)-3,7-dimethylxanthine (0.05 mol) and trimethylsilylazide (0.06 mol) in pentane (50 ml). After 24 hours at room temperature the mixture was poured into 100 mls of water. The organic phase was separated, washed with a 10% solution of sodium bicarbonate, and dried over sodium sulfate. The solution of the azide in pentane was stirred at 25°-30° C., and 0.05 mol of triethylphosphite was added. Stirring was continued for 6 hours, and the solution was left at this temperature for 72 hours. Solvent was evaporated off and the iminophosphorane was dissolved in ethanol (15 mls) and treated with p-toluenesulfonic acid monohydrate (0.05 mol) and water (0.05 mol). The mixture was refluxed for eight hours, evaporated and the residue diluted with 100 mls of ether. The tosyl salt of the amine was precipitated out and was recovered by filtration. Then, 30% aqueous ammonium hydroxide (20 mls) was added to the crystals and the free amine was extracted into dichloromethane (3×15 mls), dried over sodium sulfate and the solvent evaporated to yield the free amine as a viscous oil, 0.7 g with a 50% yield.

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