| Abstrakt: |
The molecular structures of three steroids, namely, 17β-acetoxy-3-methoxy-8-isoestra- 1,3,5(10)triene (I), 17β-acetoxy-3-methoxy-7α-methyl-8-isoestra- 1,3,5(10)-triene (II), and 17β-acetoxy-3-methoxy- 1 methyl-8-isoestra-1,3,5(10)-triene (III), are determined by X-ray diffraction analysis. It is shown that the substituents in the A and B rings of the compounds of the 8-iso series have a slight effect on the conformation of the steroid skeleton as a whole, which manifests itself only in insignificant distortions of the B and D rings. The methyl group in the 1-position (compound III) affects the geometric parameters of the steroid nucleus less than the same substituent in the 7-position (compound II). A sharp decrease in the uterotropic activity of compounds II and III (compared to compound I) revealed in biological studies can be attributed to unfavorable steric interactions of the substituents in the A and B rings with the estradiol receptor. [ABSTRACT FROM AUTHOR] |
