Synthesis and negative inotropic effects evaluation of 7-substituted-4,5-dihydro-[1,2,4]oxadiazolo[4,3-a]quinolin-1-ones

A series of 7-alkoxy-4,5-dihydro-[1,2,4]oxadiazolo[4,3-a]quinolin-1-ones was synthesized and their negative inotropic effects were evaluated by measuring the left atrium stroke volume in isolated rabbit heart preparations. All compounds moderated the cardiac workload by decreasing heart rate and contractility (inotropic effects). Among them, compound 6 was found to be best potent with a -28.89 +/- A 1.91 % decrease in the stroke volume at a concentration of 3 x 10(-5) M in our in vitro study.