Synthesis and estrogen receptor binding of (17α,20E)-and (17α,20Z)-21-phenylthio-and 21-phenylseleno-19-norpregna-1,3,5(10),20-tetraene-3,17β-diols

Article abstract of DOI:10.1016/0039-128X(96)00045-1

Previous studies fron our laboratory using 17α-E-and 17α-Z-halovinyl estradiols demonstrated a marked enhancement of receptor binding by the Z-isomers. This suggested tolerance at the 17α-position was not previously observed by investigations using 16α and 17α-substituted estradiols. Because of the synthetic access provided by vinyl tin chemistry, we prepared the 17α-E and Z-phenylthiovinyl and phenylselenovinyl estradiols and compared their binding characteristics to those of the previously reported 16α/17α-phenylseleno and methylseleno estradiols. The results, in addition to demonstrating a facile preparation of the target compounds, indicated that signific int receptor affinity was retained by these compounds (relative binding affinity = 24.5-117). The highest affinity was demonstrated by the 17α-Z-phenylthiovinyl estradiol 5a, which, by molecular modeling, exhibited a significantly different molecular conformation from the corresponding 17α-E-phenylthiovinyl isome, or the 17α-phenyl-thioethynyl analog. The current series possessed better binding characteristics than the phenylseleno and methylseleno estradiols but somewhat poorer binding than the 17α-E/Z-halovinyl series. The observations suggest that some steric limitations exist in a portion of the 17α-region, and that the region is better accessed by compounds possessing Z-vinyl stereochemistry.