Synthesis and biological activities of nucleoside–estradiol conjugates

Nucleosides were coupled to estradiol via a 17α-ethynyl spacer group using Pd(II) as a catalyst. The conjugates were evaluated in vitro for estrogen receptor (ER) binding affinity and cytotoxicity against cell lines with and without ER. The highest receptor binding affinities (RBA 3) were observed with conjugates coupled via a relative long spacer group, while none of the conjugates exhibited cytotoxicity against either cell lines.