Scheme 3.
3-(3,5-Dimethyl-1-(3-methyl-[1,2,4]-triazolo-[4,3-b]-pyridazin-6-yl)-1H-pyrazol-4-yl)-propanoic acid. To a solution of methyl 3-(3,5-dimethyl-1-(3-methyl-[1,2,4]triazolo[4,3-b]pyridazin-6-yl)-1H-pyrazol-4-yl)propanoate (175 mg, 0.557 mmol) in THF (1.75 ml) and water (0.7 ml) was added LiOH·H2O (70.16 mg, 1.671 mmol). The reaction mixture was stirred at room temperature for 20 h. A 3 n HCl solution (8 ml) was added, and the mixture was extracted with a mixture of 20% isopropyl alcohol in dichloromethane (3×). The combined organic layers were dried over magnesium sulfate, filtered, and concentrated in vacuo. The white solid obtained (140 mg, 84%) was used without further purification. 1H NMR (400 MHz, DMSO-d6): δ 12.19 (s, 1H), 8.36 (d, J = 10 Hz; 1H), 7.85 (d, J = 10 Hz; 1H), 2.76–2.66 (br m, 5H), 2.6 (s, 3H), 2.55–2.48 (br m, 2H), 2.24 (s, 3H); LC-MS (ESI+) m/z: [M + H]+ Calcd. for C14H17N6O2 301.32 found 301.40, tR = 0.84 min.