Discovery of 7-(Prolinol-N-yl)-2-phenylamino-thiazolo[5,4-d]pyrimidines as Novel Non-Nucleoside Partial Agonists for the A_2A Adenosine Receptor: Prediction from Molecular Modeling

Abstract

We describe the identification of 7-(prolinol-N-yl)-2-phenylamino-thiazolo[5,4-d]pyrimidines as a novel chemotype of non-nucleoside partial agonists for the A2A adenosine receptor (A2AAR). Molecular-modeling indicated that the (S)-2-hydroxymethylene-pyrrolidine could mimic the interactions of agonists' ribose, suggesting that this class of compounds could have agonistic properties. This was confirmed by functional assays on the A2AAR, where their efficacy could be associated with the presence of the 2-hydroxymethylene moiety. Additionally, the best compound displays promising affinity, selectivity profile, and physicochemical properties.

Structural Mapping of Adenosine Receptor Mutations: Ligand Binding and Signaling Mechanisms

“…A majority of the mutational data collected refers to orthosteric ligand binding, where combinations of SDM and crystal structures led to the design of AR antagonists [79], and novel computational protocols have provided with detailed energetic descriptions of ligand binding. Still, some issues remain unsolved with regard to ligand optimization, such as achieving better selectivity ratios or attaining an agonist functional response on ligands lacking a ribose moiety, though recent advances in this regard are promising [80]. Allosteric modulation is a promising pharmacological strategy to overcome some of these issues, but while there is indirect evidence pointing to the location of allosteric sites on the EL region, a crystal structure with an allosteric modulator is still lacking.…”

Structure-Based Design of Potent and Selective Ligands at the Four Adenosine Receptors

“…During the last years, our labs have combined FEP and other computational methodologies with high-throughput synthetic methodologies and pharmacological characterization, to develop various series of structurally simple, novel AR ligands [ 23 ]. Our SBDD protocol includes homology modeling, protein–ligand docking, 3D-QSAR, MD and FEP simulations, and was used to assist the design of novel ligands as well as to predict or rationalize their pharmacological profile [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. The different series obtained with this strategy, represented in Figure 1 , have been optimized to yield potent and selective antagonists of the different ARs.…”

“…Consequently, we used this system to train our protocol for in-silico mutagenesis, based on well-converged FEP calculations [ 20 , 21 ]. Moreover, we went one step further in the design of new ligands and isolated, from a series of antagonists, a group of compounds that presented a pharmacological profile of partial agonists, where we identified a prolinol moiety as a replacement of the ribose group of classical agonists [ 28 ]. Finally, recently published crystal structures of the A 1 AR allow for the characterization of molecular determinants of high affinity, which we here exemplify with the calculation and interpretation of the effect of point mutations on the binding affinity of the reference xanthine-like antagonist DPCPX (see Figure 1 ).…”

Non-Nucleoside Agonists of the Adenosine Receptors: An Overview

“…The S-alkyl isothioureas IX was then reacted with the benzylidene-malononitriles in ethanol and in the presence of sodium bicarbonate to furnish the desired compounds VIII (Scheme 4) [97]. Starting from 2008, Cosimelli and coworkers published a series of compounds with agonist properties for ARs characterized by a common 6-alkoxypyrimidine scaffold [79,80,98]. The synthesis of such compounds was obtained by alkylation of the sulfur atom in the 2-position of the commercially available 4-amino-6-hydroxy-2-mercaptopyrimidine with the suitable alkyl halide in an aqueous solution of sodium hydroxide (Scheme 5).…”

“…These compounds (lacking the 5-cyano group and an aromatic ring within the 6-substituent) showed antagonist activity at the ARs [79]. In a successive work, the same authors tested analogues of these molecules based on a pyrimidine scaffold, with the presence of a phenylmethyloxy chain in the 6-position [80]. Biological evaluation of these compounds showed that they are endowed with micromolar affinity for the A 1 AR and high nanomolar agonist potency at the same AR subtype (43-44; Figure 2; Table 2).…”