Journal of medicinal chemistry
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Various substituted isoquinoline-1-carboxaldehyde thiosemicarbazones (12 compounds) have been synthesized and evaluated for antineoplastic activity in mice bearing the L1210 leukemia. Condensation of 4-bromo-1-methylisoquinoline (4) with ammonium hydroxide, methylamine, ethylamine, and N-acetylethylenediamine gave the corresponding 4-amino, 4-methylamino, 4-ethylamino, and 4-N-(acetylethyl)amino derivatives, which were then converted to amides and subsequently oxidized to aldehydes followed by condensation with thiosemicarbazide to yield thiosemicarbazones 8a-c, 9a-c, and 16. Nitration of 4, followed by oxidation with selenium dioxide, produced aldehyde 18, which was then converted to the cyclic ethylene acetal 19. ⋯ Condensation of compounds 32 and 39 with thiosemicarbazide afforded the respective 4- and 5-acetoxy(5- and 4-methyl)thiosemicarbazones 33 and 40, which were then converted to their respective 4- and 5-hydroxy derivatives 34 and 41 by acid hydrolysis. The most active compounds synthesized were 4-aminoisoquinoline-1-carboxaldehyde thiosemicarbazone (9a) and 4-(methylamino)isoquinoline-1-carboxaldehyde thiosemicarbazone (9b), which both produced optimum % T/C values of 177 against the L1210 leukemia in mice when used at a daily dosage of 40 mg/kg for 6 consecutive days. Furthermore, when 9a was given twice daily at a dosage of 40 mg/kg for 6 consecutive days, a T/C value of 165 was obtained and 60% of the mice were 60-day long-term survivors.