Hydrochloric Acid → 6-(Tert-butoxycarbonyl)-3-dimethylamino-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-2,4-dione

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Reaction Steps

Ethyl-4-phenoxycarbonylamino-1-tert-butoxycarbonyl-1,2,5,6-tetrahydropyridine-3-carboxylate (5.0 g) was dissolved in THF (50 ml) and dimethyl hydrazine (1.46 ml) and DBU (0.2 ml) were added and the resultant mixture was stirred at room temperature for 2 hours. Dimethylhydrazine (0.73 ml) and DBU (0.2 ml) were added and the resultant mixture was further stirred at room temperature for 2 hours. After production of an intermediate (urea) was confirmed by TLC, a 5 N aqueous sodium hydroxide solution (5 ml) was added and the resultant mixture was further stirred at room temperature overnight. To the reaction solution, 6 N hydrochloric acid was added to neutralize and the resultant mixture was then concentrated. To the residue, water was added and the mixture was extracted with ethyl acetate. After the organic layer was washed with a saturated saline solution, the organic layer was dried over sodium sulfate, filtrated and concentrated. The resultant residue was purified by medium-pressure silica gel column chromatography (solvent; ethyl acetate:hexane=50:50 to 100:0). To the resultant amorphous substance, diethyl ether was added to obtain a precipitate by filtration. The titled compound (3.34 g) was obtained as a white powder.

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