The structure of 4',4''-diethylstilbestrol (DES) quinone

The structure of 4',4''-diethylstilbestrol quinone (DES quinone), a short-lived metabolic intermediate of the synthetic estrogen E-diethylstilbestrol (DES), was investigated by 13C- and 1H-nmr. Selected homonuclear decoupling experiments were carried out to identify the carbons and protons with which resonances were associated. The 1H-nmr spectrum of DES quinone remained unchanged in the temperature range from 25 degrees C to 65 degrees C. The spectral results suggested the structure of DES quinone to be planar or time-averaged planar with the exception of the freely rotating ethyl groups. The conformation of this intermediate was found to be transoid without any indication of conversion through a cisoid conformation. The similarity of the 1H-nmr spectrum of 3',3'',-5',5''-tetrafluoro-4',4''-diethylstilbestrol quinone (TF-DES quinone) and that of the non-fluorinated parent suggested a high degree of structural similarity. The planar structures of the quinone intermediates differed from those of DES or Z,Z-dienestrol which were not coplanar with respect to the aromatic ring systems.