Isomerization of trans-diethylstilbestrol to pseudo-diethylstilbestrol

This study reports the formation and isolation of a diethylstibestrol-dimethylsulfoxide (DES-DMSO) adjunct and Z-3, 4-di (p-hydroxyphenyl)-2-hexene (psi-DES) from trans-DES. The presence of psi-DES was indicated by NMR and mass spectrometry and confirmed by direct comparison to a reference sample. High resolution NMR (360 MHz) along with the comparison of the chemical shift values of methine and methyl protons attached to carbon-carbon double bonds in Z and E isomers of 3-substituted-2-pentenes and dienestrol derivatives were used in postulating the Z-stereochemistry for psi-DES. A NMR additive increment method was useful for the comparison of the chemical shift values of methine protons in psi-DES and other literature compounds. Nuclear Overhauser Enhancement (NOE) confirmed the Z-stereochemistry of psi-DES.