7-(4-hydroxybutyl)-1,3-dimethylpurine-2,6-dione

1,3-dimethyl-7-(2-piperidin-1-ylethyl)purine-2,6-dione

1,3-dimethyl-7-phenylpurine-2,6-dione

1,3,7-trimethyl-8-nitropurine-2,6-dione

1,3-dimethyl-2-oxo-8-pyridin-1-ium-1-ylpurin-6-olate