Abstract
Separating the stereospecific factor from others governing the manifestation of biological activity to estimate its relative significance is the first step in understanding the stereospecific effect of biologically active compounds. In certain cases, this can be performed by means of quantitative structure-activity-relationship of congeneric series of bioactive compounds using physical-organic models and multiple regression analysis. Examinations were made for the use of the Taft Es and the Hancock Esc parameters as the model of intra- as well as inter-molecular steric effects. Quite a few congeneric series of bioactive compounds were successfully analyzed using these free -energy-related parameters. The comparison was made with other steric parameters currently used in structure-activity studies.