Structure-activity relationship of 3,3'-dihydroxy-alpha,beta-diethyldiphenylethane and its related compounds

3,3'-Dihydroxy-alpha,beta-diethyldiphenylethane (I), 3,3'-dihydroxy-alpha,beta-diethylstilbene (II), hexestrol (III) and diethylstilbestrol (IV) have already been reported to show hypotensive effects on rats and exhibit phytogrowth-inhibitory activities. We have proposed that two phenolic hydroxyl groups in these compounds are necessary for the biological activities, and a structure-activity relationship for I-related compounds was accomplished using molecular-mechanics (MM) calculations. As a result, the following three findings were obtained; 1) the minimized conformational energy obtained from MM calculations, which is a parameter expressing the molecular stability, showed a relatively high correlation with the biological activities, 2) as results of quantitative structure-activity relationship (QSAR) analyses, the combination of the distance between two phenolic hydroxyl oxygens led to the regression equations with high correlation values, and 3) the idealized molecular model of the most active compound (I) showed the highest stability and had a particular conformation which differed from the other compounds (II-IV).