Easy Access to 1H-Pyrrolo[3′,4′:5,6]pyrido[2,3-d]pyrimidine-2,4,6,8(3H,7H)-tetraone and Selectively N7-Substituted Analogues through Key Synthons

To synthesize unsubstituted pyrrolo[3′,4′:5,6] pyrido[2,3-d]pyrimidine-2,4,6,8-tetraone, we have developed new synthon 4-formyl-3-hydroxy-2,5-dioxo-2,5-dihydro-1H-pyrrole, which was then treated under mild conditions with 6-aminouracil. This new synthetic pathway could be extended to the preparation of N7-selectively substituted heterocycles by starting either from this new synthon or from its N-substituted analogues. Examples of N1,N7-disubstituted and N1,N3,N7-trisubstituted derivatives are also described. We have thus developed new synthons that lead to easy access to the unsubstituted pyrrolo[3′,4′:5,6]pyrido[2,3-d]pyrimidine-2,4,6,8-tetraone skeleton and to selectively N7-substituted analogues.