Synthesis and pharmacokinetics of 131I labeled benzoyl derivatives of estrone and estradiol.

3-(2-[131I]iodobenzoyl)estradiol-17 beta (1), 3-(2-[131I]iodobenzoyl)estrone (2) and 17 beta-(2-[131I]iodobenzoyl)-estradiol (3) have been prepared by bromine-iodine exchange followed by preparative HPLC in radiochemical yields greater than 70% (isolated). The specific activities were greater than 200 Ci/mmol. Tissue distribution studies in DMBA-induced tumor bearing rats showed a rapid clearance via the kidneys and poor accumulation in the target tissues. The relative binding affinities to the estrogen receptor were estimated as 3.5% 1, 1.7% 2 and 0.05% 3 of the affinity of estradiol (100%).