Synthesis and anticonvulsant activity of new N-phenyl-2-(4-phenylpiperazin-1-yl)acetamide derivatives

Abstract

Twenty-two new N-phenyl-2-(4-phenylpiperazin-1-yl)acetamide derivatives have been synthesized and evaluated for their anticonvulsant activity in animal models of epilepsy. These molecules have been designed as analogs of previously obtained anticonvulsant active pyrrolidine-2,5-diones in which heterocyclic imide ring has been changed into chain amide bound. The final compounds were synthesized in the alkylation reaction of the corresponding amines with the previously obtained alkylating reagents 2-chloro-1-(3-chlorophenyl)ethanone (1) or 2-chloro-1-[3-(trifluoromethyl)phenyl]ethanone (2). Initial anticonvulsant screening was performed using standard maximal electroshock (MES) and subcutaneous pentylenetetrazole screens in mice and/or rats. Several compounds were tested additionally in the psychomotor seizures (6-Hz model). The acute neurological toxicity was determined applying the rotarod test. The results of pharmacological studies showed activity exclusively in the MES seizures especially for 3-(trifluoromethyl)anilide derivatives, whereas majority of 3-chloroanilide analogs were inactive. It should be emphasize that several molecules showed also activity in the 6-Hz screen which is an animal model of human partial and therapy-resistant epilepsy. In the in vitro studies, the most potent derivative 20 was observed as moderate binder to the neuronal voltage-sensitive sodium channels (site 2). The SAR studies for anticonvulsant activity confirmed the crucial role of pyrrolidine-2,5-dione core fragment for anticonvulsant activity.

Keywords: Anticonvulsant activity; Epilepsy; In vitro studies; In vivo studies; Phenylacetamides; SAR studies.

Fig. 1

Structures of known AEDs containing nitrogen heterocyclic ring

Fig. 2

Structures of model pyrrolidine-2,5-diones obtained in the previous research

Fig. 3

Structures of known AEDs containing chain amide bound

Fig. 4

The exchange of the pyrrolidine-2,5-dione core fragment for chain amide bound

Scheme 1

Synthetic pathways of intermediates 1, 2 and target compounds 3–24

Fig. 5

The HPLC chromatogram of compound 22