Isovaleryl chloride → 3-(3-Methyl-butyrylamino)-pyrazine-2-carboxylic acid

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Reaction Steps

3-(3-Methyl-butyrylamino)-pyrazine-2-carboxylic acid benzylamide: To a solution of DMF (200 mL), 3-aminopyrazine-2-carboxylic acid (10.0 g, 71.9 mmol) and diisopropylethyl amine (25.0 mL, 144 mmol) was added isovaleryl chloride (12.4 mL, 86.3 mmol) dropwise at room temperature. The reaction mixture was stirred at room temperature for two hours after which the solvent was removed under reduced pressure and the residue dried under vacuum overnight, to afford 3-(3-methyl-butyrylamino)-pyrazine-2-carboxylic acid as a solid residue. The solid residue was dissolved in acetic anhydride (200 mL) and the mixture stirred at 100° C. overnight. The excess acetic anhydride was removed by distillation under reduced pressure, leaving a residue that was then cooled to room temperature and washed with hexane to give the corresponding oxazinone compound of Formula 103, 2-isobutyl-pyrazino[2,3-d][1,3]-oxazin-4-one, which was carried forward without additional purification. A solution of chloroform (200 mL), the oxazinone of Formula 103, and benzylamine (16.0 mL, 144 mmol) was stirred at 60° C. for two hours. After the complete consumption of the oxazinone, as monitored by reverse phase HPLC, the chloroform was removed under reduced pressure and the residue purified by silica gel chromatography using hexane-EtOAc (1:2) as eluent to obtain the title bis amide, 3-(3-methyl-butyrylamino)-pyrazine-2-carboxylic acid benzylamide (4.5 g 20.0%, three steps). MS (Cl) M/E: 313.1.

Provenance & Evidence