Several new 4-diazopyrazole derivatives were synthesized by reaction o
f R-substituted)phenyl-3-methyl-5-benzamidopyrazoles with a sevenfold
excess of nitrous acid in acetic media. The compounds were tested at 2
0 mu M concentration for their antineoplastic activity in vitro agains
t Raji (human Burkitt lymphoma), K562 (human chronic myelogenous leuke
mia) and U937 (human histiocytic limphoma) cell lines. They showed a p
ercent of growth inhibition in the range 23.4-100%.