Synthesis, receptor binding and target-tissue uptake of carbon-11-labeled carbamate derivatives of estradiol and hexestrol

Carbon-11-labeled estradiol and hexestrol derivatives were prepared via the reaction of [¹¹Cethylchloroformate with the 2- and 4-amino derivatives of estradiol, the 3′-amino derivatives of hexestrol, and the 1-aminophenoxy derivatives of hexestrol and 1-norhexestrol. The corresponding nonradioactive carbamates were prepared for chemical characterization and in vitro receptor binding assays. The positions of the substituents on the parent molecules were selected with a view to minimize interference with the receptor binding process. In spite of this, affinity for the estrogen receptor was strongly impaired for all carbamate derivatives. Likewise, in vivo, the [¹¹C]carbamate analogs failed to localize in receptor rich tissue via an estrogen receptor mediated process.