Abstract: The Hansch approach was used in the quantitative structure anticonvulsant activity studies of the previously synthesized 1-substituted-and 1.5-disubstituted-3-pyrazo-lidinones. Correlation analysis predicted that 1.5-disubstituted-3-pyrazoljdinones in which 1- substituent is n-propyl but not benzyl, with the total hydrophobic constant of 1-and 5-substituents (∑л) equals to 4.5 (optimum value) will have the most potent activity. On the basis of this analysis eleven 5-substituted and I-n-butyl-5-substituted-3-pyrazolidinones were synthesized. Pharmacological tests indicated that the prediction of the Hansch analysis of the 3-pyrazolidinones is correct. The Hansch analysis, by including these 11 compounds, gives an almost identical correlation with that previously obtained.

Key words: 3-Pyrazolidinones, Anticonvulsant activity, QSAR