Synthesis and pharmacological evaluation of pyrrolidin-2-one derivatives as antiarrhythmic, antihypertensive and alpha-adrenolytic agents.

A series of novel arylpiperazines bearing a pyrrolidin-2-one fragment were synthesized and evaluated for their binding affinity for alpha1- and alpha2-adrenoceptors (ARs) as well as their antiarrhythmic and antihypertensive activities. The highest affinity for the alpha1-AR was displayed by 1-{3-[4-(2-chloro-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one 7, which binds with a pKi = 7.13. The highest affinity for the alpha2-AR was shown by 1-{3-[4-(4-chloro-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one 18, which binds with a pKi = 7.29. Among the compounds tested, 1-{3-[4-(2-ethoxy-phenyl)-piperazin-1-yl]-propyl}-pyrrolidin-2-one 13 had the highest prophylactic antiarrhythmic activity in epinephrine-induced arrhythmia in anesthetized rats. Its ED50 value was 1.0 mg/kg intravenously (iv). The compounds with a hydroxy group in the 4-position of the phenyl ring or two substituents such as fluorine atoms in the 2 and 4 positions of the phenyl ring significantly decreased systolic and diastolic pressure in normotensive anesthetized rats at a dose of 2.5 mg/ kg iv, and their hypotensive effects lasted for longer than an hour.