METAL-MARKED STEROIDS OF THE ESTRANE GROUP FROM THE REACTION OF STEROIDAL FUNCTIONAL-GROUPS WITH ARENE-IRON(CP) COMPLEXES

Reaction of -p-chlorotoluene)(eta(5)-cyclopentadienyl)iron(II) hexaflu orophosphate with the phenolic hydroxy group of estrane steroids, unde r mild conditions, leads to the formation of 3-O-p-tolyl ethers of ste roids, with an iron(Cp) marker. Employing this reaction, estrone, estr adiol and 17-alpha-ethynylestradiol have been marked in high yield. Th e utility of such marked steroids in metalloimmunoassay has been exami ned. Steroids marked in such a way show no measurable affinity for the estradiol receptor. The 3-O-p-tolylestrone complex is stable at room temperature for 24 h, in water solutions of buffers at pH 2.0 and 7.41 , as well as in a THF solution in the presence of pyrrolidine. The mar ker fragment may be removed at room temperature upon the action of pyr rolidine in a 1:1 water-THF solution or potassium hydroxide in water f or 24 h with the efficient recovery of steroid. Treatment of marked es trone with an excess of potassium t-butoxide leads to demetallation an d the formation of 3-O-p-tolylestrone. Attempts to mark estrone and te stosterone via the carbonyl group or estradiol and cholesterol via the secondary hydroxyl group, under mild conditions, have been unsuccesfu l.