Effect of Nitrogen Atom Substitution in A(3) Adenosine Receptor Binding : N-(4,6-Diarylpyridin-2-yl)acetamides as Potent and Selective Antagonists

We report the first family of 2-acetamidopyridines as potent and selective A, adenosine receptor (AR) antagonists. The computer -assisted design was focused on the bioisosteric replacement of the N1 atom by a CH group in a previous series of diarylpyrimidines. Some of the generated 2-acetamidopyridines elicit an antagonistic effect with excellent affinity (K-j < 10 nM) and outstanding selectivity profiles, providing an alternative and simpler chemical scaffold to the parent series of diarylpyrimidines. In addition, using molecular dynamics and free energy perturbation simulations, we elucidate the effect of the second nitrogen of the parent diarylpyrimidines, which is revealed as a stabilizer of a water network in the binding site. The discovery of 2,6-diaryl-2-acetamidopyridines represents a step forward in the search of chemically simple, potent, and selective antagonists for the hA(3)AR, and exemplifies the benefits of a joint theoretical- experimental approach to identify novel hA(3)AR antagonists through succinct and efficient synthetic methodologies.