Pyrazolo[3,4-d]pyrimidine ribonucleosides as anticoccidials. 2. Synthesis and activity of some nucleosides of 4-(alkylamino)-1H-pyrazolo[3, 4-d]pyrimidines.

A series of 4-(alkylamino)-1-beta-D-ribofuranosyl-1H-pyrazolo[3, 4-d]pyrimidines was synthesized by enzymatic and chemical methods. On the basis of the previous finding that 4-(alkylthio)-1-beta-D-ribofuranosyl-1H-pyrazolo[3,4-d]pyrimidines were effective anticoccidial agents, this series was examined for efficacy against Eimera tenella in chicks. The most active anticoccidial agent in the present study was the 4-cyclopentylamino derivative (8), which cleared chicks of the parasite at 200 ppm in the diet. Some members of this series were toxic to embryonic chick liver cells, mouse cells, and human cells in vitro. The 4-diethylamino derivative (16), which was not toxic in vitro, appeared to be toxic in chicks.