The Use of a Crown Ether to Synthesize a Fluorine-18 Labeled Steroid
Previous work in this laboratory has shown that 18F-fluoride can be incorporated into useful radiopharmaceuticals. The reaction of 21-hydroxy-4-pregnene-3, 20-dione-21-methanesulfonate with K18F in the presence of 18-Crown-6 was studied. As the relative molar amount of crown ether was increased up to eight times the amount of precursor steroid, the radiochemical yield of 18F-labeled steroid increased. However, the radiochemical yield fell off with larger amounts of crown ether. Using the optimum conditions, 21-18F-fluoroprogesterone was prepared with a radiochemical yield of 23%. Thus 125 µCi of labeled steroid were obtained when 1.0 mCi of K18F was allowed to react for 2 h. The specific activity of the labeled steroid was calculated to be 20 Ci/mol.
KeywordsCrown Ether Molar Amount Radiochemical Yield Potassium Fluoride Precursor Steroid
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