A number of 2-phenylindole derivatives with one hydroxy group in the meta or para position of the phenyl ring and a second one in position 5, 6, or 7 of the indole nucleus were synthesized. In addition, different alkyl groups were introduced into positions 1 and 3 of the heterocycle. The influence of these structural variations on the binding affinity for the calf uterine estrogen receptor was studied. A prerequisite for the binding is the presence of an ...