AbstractThe highly estrogen receptor(ER)‐affinic compound 1,1‐bis(4‐hydroxy‐phenyl)‐2‐phenylethene (BHPE) was used as carrier ligand for a new cis‐platin derivative, aqua[1,1‐bis(4‐hydroxyphenyl)‐1,2‐diamino‐2‐phenyl‐ethane]sulfatoplatinum(II) (3‐PtSO4) for the therapy of the ER‐positive (i.e.hormone sensitive) breast cancer. The diamine ligand 1,1‐bis(4‐hydroxyphenyl)‐1,2‐diamino‐2‐phenylethane (3) was synthesized by transformation of theO‐methyl ether derivative of BHPE into the 1,2‐bisazido compound3bwith IN3/NaN3, reduction of both N3residues into NH2groups [3a] and subsequent ether cleavage with BBr3. From the diamine ligand3and K2PtI4a five‐membered chelate3‐PtI2was obtained which was transformed into3‐PtSO4with Ag2SO4. In comparison to BHPE the ER‐affinity of3‐PtSO4is markedly reduced.3‐PtSO4possesses, however, weak cytotoxic activity (P388) and antiestrogenic, but no estrogenic properties.3‐PtSO4is comparable with BHPE in terms of its activity