Diethylstilbestrol-linked cytotoxic agents: synthesis and binding affinity for estrogen receptors

The syntheses of diethylstilbestrol derivatives with a C4 side chain at the double bond bearing various functional and potentially alkylating groups (9-25, 38-40, 43, 44) as well as the coupling product with daunorubicin (41) are described. Derivatives with free phenolic groups show easy isomerization to (Z)-stilbenes and styrenes, which could be minimized with silyl protecting groups. Estrogen receptor binding is decreased by polar groups such as carboxylic acids (10) as well as sterically demanding substituents.