Allosteric Modulators of the Adenosine A₁ Receptor: Synthesis and Pharmacological Evaluation of 4-Substituted 2-Amino-3-benzoylthiophenes

Abstract

A series of 4-substituted 2-amino-3-benzoylthiophenes was screened using a functional assay of A(1)AR-mediated phosphorylation of ERK1/2 in intact CHO cells to identify both potential agonistic effects as well the ability to allosterically modulate the activity of the orthosteric agonist, R-PIA. More detailed concentration-response experiments were subsequently performed on two compounds (9a and 9o) utilizing both the ERK1/2 assay as well as a second assay of [(35)S]GTPgammaS binding to activated G proteins.

Separation of on-target efficacy from adverse effects through rational design of a bitopic adenosine receptor agonist

“…Equilibrium radioligand binding, [ 35 S]GTPγS binding, cAMP accumulation, and ERK1/2 phosphorylation assays were performed as described previously (23,33) and in SI Materials and Methods. Cell Viability Assay and Imaging.…”

“…1A and Fig. S1), with the hypothesis being that the adenosine moiety would confer high efficacy to the hybrids, whereas the VCP171 moiety would induce biased signaling (23). Although the location of the allosteric site on the A 1 AR has not been definitively determined, it is thought to comprise residues that are more extracellular to the orthosteric site (27)(28)(29).…”

“…The introduction of bulky substituents at the four and five positions of the thiophene ring of 2-amino-3-benzoylthiophene modulators can also preserve or enhance their allosteric properties (23,(33)(34)(35). We, thus, generated six hybrid ligands by attaching the N 6 of adenosine to the five position of the thiophene ring of VCP171 with a 4-benzamidoalkyl linker that ranged from 2 to 12 carbon atoms in length (Fig.…”

“…Although no study has identified biased orthosteric A 1 AR ligands, we recently showed that the 2-amino-3-benzoylthiophene allosteric modulator (VCP171) could promote biased signaling in the activity of the prototypical orthosteric agonist, R(-)N6-(2-phenylisopropyl) adenosine (R-PIA) (23). Thus, we hypothesized that the rational design of a bitopic ligand (i.e., a class of hybrid molecule containing both orthosteric and allosteric pharmacophores) (24-26) may be able to achieve high efficacy and biased agonism at the A 1 AR in a single molecule.…”

Synthesis of 5-membered heterocycles using benzoylacetonitriles as synthon

“…45 2,3,4-Trimethyl-5-phenylthiophene 60 and (2-amino-4-methyl-5-phenylthiophen-3-yl)(phenyl)methanone 59 were prepared in ratio 95:5 by regioselective Knoevenagel condensation of 1 with 3-chlorobutan-2-one 58 followed by intermolecular addition in pyridine and then the Gewald reaction. 46 Aminobenzoylthiophene 61, as allosteric modulator of the adenosine A1 receptor, was prepared in 60% yield by alkylation of 1 with phenacyl bromide followed by cyclocondensation with sodium hydrosulfide. 16 2-Amino-3-benzoyl-4-phenylthiophene deriva-tives 62 as A1 adenosine receptor allosteric enhancers were prepared from the reaction of 1 with 3-trifluromethyl aceteophenone (Scheme 18).…”