Synthesis and pharmacological evaluation of new 1-[3-(4-arylpiperazin-1-yl)-2-hydroxypropyl]-pyrrolidin-2-one derivatives with anti-arrhythmic, hypotensive, and alpha-adrenolytic activity.

A series of novel arylpiperazines bearing a pyrrolidin-2-one fragment was synthesized and evaluated for the binding affinity of the alpha(1)- and alpha(2)-adrenoceptors (AR) and for the antiarrhythmic and hypotensive activities of the compounds. The most potent and selective compound 1-[2-hydroxy-3-[4-[(2-hydroxyphenyl)piperazin-1-yl]propyl]pyrrolidin-2-one 8 binds with pK(i) = 6.71 for alpha(1)-AR. Derivative 8 was also the most active in the prophylactic antiarrhythmic test in adrenaline-induced arrhythmia in anaesthetized rats. Its ED(50 )value equals 1.9 mg/kg (i.v.). Compounds with substituents such as a fluorine atom 4, a methyl 5, or a hydroxyl 8 group, or two substituents such as fluorine/chlorine atoms and methoxy groups in the phenyl ring, significantly decreased the systolic and diastolic pressure in normotensive anesthetized rats at a dosages of 5-10 mg/kg (i.v.). It was found that the presence of the piperazine ring and a hydroxy group in the second position of the propyl chain are critical structural features in determining the affinity of the compounds tested.