6-Carbohydrazonamidepurines: Convenient Precursors for 4,8-Disubstituted Pyrimido[5,4-d]pyrimidines

Pyrimido[5,4-d]pyrimidine-Based Compounds as a Novel Class of Antitrypanosomal and Antileishmanial Agents

Sleeping sickness and leishmaniasis are neglected tropical diseases that threaten millions of people. The currently available therapies present several limitations, including high toxicity, lack of efficacy, and emerging drug resistance, prompting a search for novel therapeutic agents. In this work, we designed, synthesized, and in vitro evaluated the activity of new pyrimido[5,4-d]pyrimidines against Trypanosoma brucei and Leishmania infantum (promastigote and amastigote forms). The cytotoxicity of the compounds against the THP1 cell line was also assessed. Most tested compounds presented low micromolar activity against T. brucei with IC50 values in the range between 0.9 and 13.4 μM, and one compound also showed activity against L. infantum (IC50 = 3.13 μM). Several molecules presented a selectivity index higher than 10. The most active compound against booth parasites is derivative 4c, with IC50 = 0.94 μM (SI > 107) against T. brucei and IC50 = 3.13 μM (SI > 32) against L. infantum. This data enabled the identification of a new promising molecular scaffold for developing a novel class of antitrypanosomal and antileishmanial agents.

Bicyclic 6 + 6 systems: the chemistry of pyrimido[4,5-d]pyrimidines and pyrimido[5,4-d]pyrimidines

The present study provides an overview of the chemistry and biological significance of pyrimido[4,5-d]pyrimidine and pyrimido[5,4-d]pyrimidine analogs as types of bicyclic [6 + 6] systems. The main sections include: (1) synthesis methods; (2) the reactivities of the substituents linked to the ring carbon and nitrogen atoms; and (3) biological applications. A discussion demonstrating the proposed mechanisms of unexpected synthetic routes is intended. The aim of this study is to discuss the synthetic significance of the titled compounds and to establish the biological characteristics of this class of compounds as studied to date, where the compounds have been applied on a large scale in the medical and pharmaceutical fields. This survey will help researchers in the fields of synthetic organic and medicinal chemistry to undertake and improve new approaches for the construction of new standard biological components.