Methyl iodide → 3-Benzyloxy-5-methyl-4-oxo-7-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylic acid

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Reaction Steps

To a solution of methyl 3-benzyloxy-4-oxo-7-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine-2-carboxylate (28 mg, 0.074 mmol) in anhydrous DMF under inert atmosphere was added sodium hydride (3 mg, 0.111 mmol, 95% dispersion in oil). The mixture was treated with iodomethane (6 μL, 0.089 mmol) and stirred at room temperature for 1 hour. When the methylation was complete, several drops of H2O were added and the mixture stirred at room temperature for 1 hour. The mixture was purified by reverse phase chromatography on a C-18 column using a gradient elution of 95-5% H2O (0.1% TFA)/CH3CN (0.1% TFA). Collection and concentration of the appropriate fractions yielded the title product as a white solid. 1H NMR (400 MHz, d6-DMSO) δ 12.90 (s, 1H), 7.51-7.49 (m, 2H), 7.39-7.31 (m, 6H), 7.01-7.00 (m, 2H), 5.80 (s, 1H), 5.27 (dd, J=11.2, 25.2 Hz, 2H), 4.21 (d, J=4.8 hz, 1H), 4.18 (d, J=4.4 Hz, 1H), 2.92 (s, 3H); ES MS (M+1)=378.

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