21-(Fluoro-18F)-17-Hydroxypregna-1,4-Diene-3,11,20-Trione

F-18-fluorohydroxypregna-1,4-diene-3,11,20-trione (FHP) is a positron emission tomography (PET) radiopharmaceutical that binds to estrogen receptors. It is used in the diagnosis of cancer and other diseases. FHP is synthesized by reduction of its carbonyl group with sodium borohydride and then converted to the desired radiolabeled form. The synthesis of FHP can be accomplished in a variety of ways, depending on the desired radionuclide and labeling technique. One such method uses an unlabeled precursor estrone or 17β-estradiol as the starting material. This precursor undergoes enzymatic conversion by testosterone 17β hydroxylase to yield FHP. A second method for synthesis begins with the conversion of estrone or 17β-estradiol to their 3α,17β-dihydroxy derivatives by