Synthesis and in vitro cytotoxicity of 3-substituted-1,8-diazaanthraquinones produced by Lewis-acid catalyzed hetero diels-alder reaction

A hetero Diels-Alder reaction of quinoline-5,8-dione with 1-(N,N-dimethylamino)-3-methyl-1-aza-1,3-butadiene proceeded to give 3-methyl-1,8-diazaanthraquinone (100% regioselectivity) in the presence of Lewis-acid catalyst (ZnCl2 or ZnBr2). Subsequent functionalizations of the benzylic methyl group resulted in the 1,8-diazaanthraquinone analogues as potential antitumor agents. The most active compound, 8, exhibited in vitro cytotoxic activity comparable to that of doxorubicin.