2(1H)-Quinolinones with cardiac stimulant activity. 1. Synthesis and biological activities of (six-membered heteroaryl)-substituted derivatives

Article abstract of DOI:10.1021/jm00118a034

A series of (six-membered heteroaryl)-substituted 2(1H)-quinolinones was synthesized, and structure-activity relationships for cardiac stimulant activity were determined. Most compounds were prepared by acidic hydrolyisis of a heteroaryl-2-methoxyquinoline obtained by palladium-catalyzed cross-coupling methodology. Direct reaction of a pyridinylzinc reagent with a 6-haloquinolinone also proved successful. In anesthetized dogs, 6-pyridin-3-yl-2(1H)-quinolinone (3; 50 μg/kg) displayed greater inotropic activity (percentage increase in dP/dt max) than positional isomers, and potency was maintained with either mono- or di- alkylpyridinyl substituents. Introduction of a 4- or 7- methyl group into 3 reduced inotropic activity, whereas the 8-isomer proved to be the most potent member of the series. Compound 26 and the 2,6-dimethylpyridinyl analogue (27 were approximately 6 and 3 times more potent than milrinone. Several quinolinones displayed positive inotropic activity (decrease in QA interval) in conscious dogs after oral administration (1 mg/kg), and 26, 27 were again the most potent members of the series. Compound 27 (0.25, 0.5, 1.0 mg/kg po) demonstrated dose-related cardiac stimulant activity, which was maintained for at least 4 h. No changes in heart rate were observed. Compounds 3, 4, 26, and 27 also selectively stimulated the force of contraction, rather than heart rate, in the dog heart-lung preparation. For a 50% increase in dP/dt max with 27, heart rate changed by less than 10 beats/min. In norepinephrine contracted rabbit femoral artery and saphenous vein, 27 produced dose related (5 x 10^-7 to 5 x 10^-4 M) vasorelaxant activity. The combined cardiac stimulant and vasodilator properties displayed by 27, coupled with a lack of effect on heart rate, should be beneficial for the treatment of congestive heart failure.