Theophylline and theobromine derivatives of nitrogen heterocyclic compounds

7-Theophylline derivatives with 4,6-dihydroxy-5-pyrimidinyl-, 3-oxopiperazinylmethyl- and 4-methyl-3,5-dioxopiperazinylmethyl substituents are described: they can be viewed as structural analogues of a nucleic base pair in the Hoogsteen arrangement; theobromine could be converted into the 1-(3,5-dioxo-4-pyrazolidinyl) derivative, similarly analogous to a base pair in the Watson-Crick arrangement.