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

A series of 4-substituted 2-amino-3-benzoylthiophenes was screened using a functional assay of A A(1)AR-mediated phosphorylation of ERK 1/2 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 ERK 1/2 assay as well as a second assay of [S-35]GTP gamma S binding to activated G proteins.