Ultrasound Promoted Synthesis of 2,3-bis-(4-Hydroxyphenyl)-indoles as Inherently Fluorescent Ligands for the Estrogen

A series of 2,3-bis-(4-hydroxyphenyl)-indoles (4c-f) was prepared by ultrasound promoted intramolecular cyclodehydration of a -anilinyl (or m-anisidyl)-desoxyanisoins (2c-f) and their optical spectroscopy and receptor binding properties have been investigated. These compounds showed intense long wavelength fluorescent emission which is sensitive to solvent polarity and pH. However, their binding affinities to ER is modest, except of 2,3-bis-(4-hydroxy-phenyl)-1-methyl-1H-indol-6-ol (4e) which has reasonably good affinity and may be used for further development.