Synthesis and receptor-binding affinity of fluorotamoxifen, a possible estrogen-receptor imaging agent

Aminotamoxifen was totally synthesized from p-nitrobenzoyl chloride via a Friedel-Crafts acylation. Then, by means of a Balz-Schiemann reaction, aminotamoxifen was converted into fluorotamoxifen. The triazene variation of this conversion, with a 25% yield, enables a rapid, one-step diazotization, incorporating a fluorine atom into the phenyl ring of the tamoxifen. This reaction may be useful for the preparation of low specific activity 18F-labeled tamoxifen, for distribution, and for estrogen-receptor studies. For these in vivo and in vitro studies, fluorotamoxifen was also synthesized from p-fluorobenzoyl chloride, and its chemical intermediates were compared with estradiol and hexestrol, for their receptor binding and competition, as well as for their uterotropic activity. It is demonstrated that tamoxifen and fluorotamoxifen are strong estradiol agonists and partial hexestrol agonists, while aminotamoxifen is a weak estradiol and hexestrol agonist.