Abstract
The solution conformations of the novel estrogen receptor ligands (17α,20__E__)‐(p‐trifluoromethylphenyl)vinylestradiol (1) and (17α,20__E__)‐(o‐trifluoromethylphenyl)vinylestradiol (2) were investigated in 2D and 1D NOESY studies and by comparison of ^13^C NMR chemical shifts with theoretical shieldings. The ^1^H and ^13^C assignments of 1 and 2 were determined by DEPT, COSY and HMQC experiments. The conformations of the 17α‐phenylvinyl substituents of 1 and 2 are of interest because of their differing receptor binding affinities and effects in in vivo uterotrophic growth assays. A statistical method of evaluating contributing conformers of 1 and 2 from predicted ^13^C shifts of possible structures correlated fairly well with conformational conclusions derived from the NOE data. The 17α substituents of 1 and 2 apparently exist in similar conformational equilibria, suggesting that while 1 and 2 would occupy a similar receptor volume, interactions with the protein may shift the equilibrium and thereby influence the expression of the ligand. Copyright © 2003 John Wiley & Sons, Ltd.