EZ-Tamoxifene

EZ-Tamoxifene is a geometric isomer of Tamoxifen, characterized by a Z-configuration around the central ethylene bridge of the triphenylethylene core. Its structure incorporates a 4-hydroxyphenyl ring linked via a methylene group to a dimethylaminoethyl side chain, with the trans-stilbene moiety replaced by a cis (Z) configuration. This stereochemical inversion disrupts the parent drug's planar aromatic alignment, reducing its estrogenic activity. The compound arises as a synthetic byproduct during Tamoxifen manufacturing due to partial isomerization under acidic conditions. It serves as an HPLC reference standard for quantifying isomeric impurities in Tamoxifen formulations.