Unexpected products of the reaction of purine nucleic base perchlorates with acetylacetone causing single-strand breaks in the DNA molecule

The reactions of purine nucleic base perchlorates with the simplest 1,3-diketone – acetylacetone – were studied for the first time. It was demonstrated that adenine reacts with acetylacetone in a 1:2 molar ratio via opening of the pyrimidine fragment of the bicyclic struc- ture, elimination of a one-carbon fragment in the form of a formic acid molecule, and recyclization into 8-(4,6-dimethylpyrimidin-2-yl)- 2,4-dimethylimidazo[1,5-a]pyrimidine. Guanine, in turn, reacted with acetylacetone in a 1:1 ratio and formed 7,9-dimethyl-3H-pyrimido- [2,1-b]purin-10-ium-4-olate. In this case, the direction of heterocyclization differed from that observed in the reaction of guanine with malondialdehyde during the in vitro and in vivo formation of the minor nucleotide base M₁G. The synthesized compounds were capable of causing single-strand breaks in DNA macromolecules.