Eleven compounds of N,N′-Bis(substitutedphenyl)-3,6-dialkyl-1,4-dihydro-s-tetrazine-1, 4-dicarboxamide were synthesised via reaction of 3,6-dialkyl-1,6-dihydro-s-tetrazine and substitutedphenyl isocyanate with yield from 24% to 86%. The antitumor activity of these compounds against P-388 and A-549 in vitro was tested. The results show that nine compounds of them showed marked antitumor activity against P-388 and seven compounds possess high antitumor activity against A-549. The IC50 of compound 3b for P-388, Bel-7402, MCF-7 and A-549 are 0.6μM, 0.6μM, 0.5 μM and 0.7μM, respectively. The substitute groups at 3, 6-position in tetrazine rings and in phenyl rings have clearly effected on their antitumor activity.
