Synthesis and Activity Investigation of Novel 1H-Purin-6(9H)-one and 3H-Imidazo[4,5-d][1,2,3]triazin-4(7H)-one Derivatives

[Image: see text] Novel 1H-purin-6(9H)-one (D) and 3H-imidazo[4,5-d][1,2,3]trazin-4(7H)-one (E) derivatives were designed, synthesized, and characterized by (1)H NMR, (13)C NMR and high-resolution mass spectrometry spectra. Their herbicidal activity bioassay showed that compound 7d exhibited relatively good activity with 70.4% inhibition rate against Amaranthus retroflexus in postemergence treatments at 1500 g/ha. Antitumor activity indicated that most of the title compounds displayed potent antitumor activity at 20 μM, among all of the promising compounds possessing lower IC(50) values than that of temozolomide, compound 7i demonstrated highest activity inhibiting both HepG-2 and U-118 MG cell lines with IC(50) values of 2.0 and 3.8 μM, respectively. The structure–activity relationship analysis revealed that introduction of halogen atoms, a bulky bridging bond between benzene ring and nitrogen atom, longer R(2) substituents could contribute to the improvement of antitumor activity. Analysis suggested that compound 7i might have potential as new highly active antitumor agent. Overall, D series had better anticancer activities than E series derivatives.