Studies on 1,2,4-benzothiadiazine 1,1-dioxides VII and quinazolinones IV: Synthesis of novel built-in hydroxyguanidine tricycles as potential anticancer agents

Two representative built-in hydroxyguanidine tricycles containing 1,2,4-benzothiadiazine 1,1-dioxides (3) and quinazolinones (4) were prepared by reductive cyclization of 1-(2-nitrophenyl-sulfonyl)-2-benzylthio-2-imidazoline (9a), 1-(2-nitrophenylsulfonyl)-2-benzylthio-1,4,5,6-tetrahydropyrimidine (9b), 1-(2-nitrobenzoyl)-2-benzylthio-2-imidazolidine (10a) and 1-(2-nitrobenzoyl)-2-benzyl-thio-1,4,5,6-tetrahydropyrimidine hydrobromide respectively (10b) with zinc dust in acetic acid under ice-cooling. 2,10-Dihydro-10-hydroxy-3H-imidazo[1,2-b][1,2,4]benzothiadiazine 5,5-dioxide (3a) and 2,3,4,11-tetrahydro-11-hydroxypyrimido[1,2-b][1,2,4]benzothiadiazine 6,6-dioxide (3b) were found to be active against solid tumor cell lines such as KB, Colo 205, HeLa, and Hepa-2.