The paper describes syntheses of 4,9-dihydro-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline (Ia), its 1-methyl derivative (Ib), 2-methyl derivative (IIa), 9-methyl derivative (Ic), 1,9-dimethyl derivative (Id) and 2,9-dimethyl derivative (IIb). Sodium salts of compounds Ia, Ib, Ic and IIa were methylated with methyl iodide in dimethylformamide at room temperature, compounds Id and IIb were demethylated with pyridine hydrochloride. The compounds prepared were tested for antiviral activity in vivo in mice against influenza virus A2-Hongkong and the Encephalomyocarditis virus.

The paper describes syntheses of 4,9-dihydro-6-methoxy-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline (Ia), its 1-methyl derivative (Ic), 1,9-dimethyl derivative (Ie), 2-methyl derivative (IIa), and 2,9-dimethyl derivative (IIc). Demethylation of these compounds with hydrobromic acid afforded 4,9-dihydro-6-hydroxy-3-methyl-4-oxo-1H(2H)-pyrazolo[3,4-b]quinoline (Ib), its 1-methyl derivative (Id), 1,9-dimethyl derivative (If), 2-methyl derivative (IIb), and 2,9-dimethyl derivative (IId) respectively. 4,9-Dihydro-6-hydroxy-3,9-dimethyl-4-oxo-1H-pyrazolo[3,4-b]quinoline (Ig) was prepared by demethylation of Ie and/or IIc with pyridine hydrochloride. The compounds prepared were tested for antiviral activity in vivo in mice against influenza virus A2-Hongkong and encephalomyocarditis virus.

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