Pyrazolopyrimidines: synthesis, effect on histamine release from rat peritoneal mast cells and cytotoxic activity

A series of 1H-pyrazolo[3,4-d]pyrimidines (3-6) substituted at positions 1 (R-1 = Ph, H, tert-butyl and ribosetribenzoate), 4 (R-2 = chlorine, nitrogen and oxygen nucleophiles), and 6 (dimethylamino) have been synthesized and their effect on the release of histamine from rat peritoneal mast cells measured. After chemical stimulation, (polymer 48/80), several compounds (i.e. 3b, 4a, 4b, 4d, 4g, 5a), produce inhibition two to three times higher (40-60%) than DSCG but this action is lower after preincubation. 4b (R-1 = Ph, R-2 = NHCH2Ph; 50-70% inhibition) and 5a (R-1 = H, R-2 = OMe, 50-55% inhibition) are the most active ones in both experiments. With ovoalbumin as stimulus, several pyrazolopyrimidines show inhibition similar to DSCG, the most active compounds being 6a-d (IC50 = 12-16 muM; R-1 = ribosetribenzoate, R-2 = methoxy and amino), Compounds 4e (R-1 = t-butyl, R-2 = OMe) and 4g (R-1 = t-butyl, R-2 = piperidino) are inducers of the release of histamine (60 and 150% increase). Compounds 4b and 4e showed cytotoxic activity (IC50 =1 mug/ml) to HT-29 human colon cancer cells. (C) 2001 Editions scientifiques et medicales Elsevier SAS.