C(N(CC)CC)C.[CH3:8][N:9]1[C:21]([CH2:22][CH:23]([CH3:25])[CH3:24])=[C:20]2[C:11]([C:12]([NH2:26])=[N:13][C:14]3[CH:15]=[CH:16][CH:17]=[CH:18][C:19]=32)=[N:10]1.Cl[C:28]([O:30][CH2:31][CH3:32])=[O:29]>ClCCl>[CH2:22]([C:21]1[N:9]([CH3:8])[N:10]=[C:11]2[C:20]=1[C:19]1[CH:18]=[CH:17][CH:16]=[CH:15][C:14]=1[N:13]=[C:12]2[NH:26][C:28](=[O:29])[O:30][CH2:31][CH3:32])[CH:23]([CH3:24])[CH3:25]Triethylamine (0.49 mL, 3.53 mmol) was added to a suspension of 2-methyl-1-(2-methylpropyl)-2H-pyrazolo[3,4-c]quinolin-4-amine (prepared as described in Example 3) (0.75 g, 2.95 mmol) in dichloromethane (30 mL) and cooled to 4° C. Ethyl chloroformate (0.352 g, 3.24 mmol) was added in dichloromethane (5 mL) dropwise over 5 minutes to the reaction mixture and maintained at ambient temperature for 16 hours. The reaction mixture was diluted with dichloromethane (25 mL) and washed sequentially with water (25 mL), 4% sodium bicarbonate (2×25 mL), water (25 mL), and brine (25 mL). The combined organic layers were concentrated under reduced pressure and the residue was purified via column chromatography on silica gel (80 g, eluting with 0-10% CMA/chloroform), concentrated under reduced pressure, and recrystallized from diethyl ether to afford 0.45 g of ethyl 1-isobutyl-2-methyl-2H-pyrazolo[3,4-c]quinolin-4-ylcarbamate as white crystals, mp 120-121° C.
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