Diimidazo[1,2-c:4′,5′-e]pyrimidines: Adenosine agonist activity demonstrated by microphysiometry

Silicon-based microphysiometry, measuring extracellular acidification rate of cells in culture, demonstrated that a series of diimidazo[1,2-c:4′,5′-e]pyrimidines were agonists at the human adenosine A1 receptor. 5-amino-7,8-dihydro-3-ribofuranose-8-(R)-(phenyl)-3H-diimidazo[1,2-c:4′,5′-e]pyrimidine (2a) had an EC50 of 100 μM and reached 90% of the Emax produced by R-PIA.