Synthesis and antischistosomal activity of certain pyrazolo[1,5-a]pyrimidines.

Several 7-hydroxypyrazolo[1,5-a]pyrimidines (1-21), 7-mercaptopyrazolo[1,5-a]pyrimidines (37-49), and 4-alkylpyrazolo[1,5-a]pyrimidin-7-ones (50-55) and the corresponding 4-alkylpyrazolo[1,5-a]pyrimidine-7-thiones (56-60) were synthesized and tested for antischistosomal activity against Schistosoma mansoni. Of the compounds examined, the greatest degree of activity in vitro was found with the 7-mercaptopyrazolo[1,5-a]pyrimidines. In particular, compounds 37 and 47 proved lethal at 100 micrograms/mL after an exposure of only 1 h. The 7-hydroxypyrazolo[1,5-a]-pyrimidines were not as active. None of the compounds exhibiting in vitro activity were active against S. mansoni in vivo.