J . Med. Chem. 1995,38,2339-2348
2339
Steroidal Affinity Labels of the Estrogen Receptor. 2. 1701-[(Haloacetamido)alkyl]estradiols Driss El Garrouj: Sigrid Aliau,+Andre Aumelas,S and Jean-Louis Borgna*,t Centre de Recherche de l'INSERM, 70 rue de Navacelles, 34090 Montpellier, France, and INSERM, U414-CNRS, UMR C9955, Facult6 de Pharmacie, 15 avenue Charles Flahault, 34060 Montpellier Cedex, France Received January 4, 1995*
In a previous study, we described affinity labeling of the lamb uterine estrogen receptor by 17a-[(bromoacetoxy)alkyYalkynyllestradiols. However, the intrinsic receptor-alkylating activities of these compounds were probably very hampered by their poor hydrolytic stability in estrogen receptor-containing tissue extracts. Therefore, (i) to develop affinity labels of the receptor not susceptible to hydrolysis and (ii) to specify the structural requirements for 17aelectrophilic estradiol derivatives to be potent afKnity labels of the receptor, we prepared four 17a-[(haloacetamido)alkyllestradiols. Three were bromoacetamides differing at the alkyl substituent (methyl, ethyl, or propyl), and the last was an [(iodoacetamido)propyllestradiol prepared under both nonradioactive and 3H-labeled forms. Although their affinities for the estrogen receptor were very low (from 0.008% to 0.02% that of estradiol), they appeared to be efficient affinity labels of the receptor due to their irreversible inhibition of [3Hlestradiol specific binding in lamb uterine cytosol. The effect of the compounds was time-, pH-, and concentrationdependent, with '50% and '80% estrogen-binding sites inactivated at 0 "C and pH 8.5, for the less active and more active compounds, respectively; the corresponding IC50 values varied from -20 nM to -10 pM. The order of efficiency was [(bromoacetamido)methyllestradiol < [(bromoacetamido)ethyl]estradiol
