title: Comparison of non-isotopic exchange methods for n.c.a. labelling of 2-iodophenyl-metyrapone.
abstract: The Cu(I)-assisted aromatic halogen exchange proved useful for preparation of macroscopic amounts of 2-iodophenyl-metyrapone as well as for the n.c.a. radioiodinated analogue. Semi-preparative HPLC-isolation provided the compound with high purity for use as chromatographic standard and for the determination of the inhibition constant of the 2-iodo-analogue. The non-isotopic exchange led to a high specific activity (> 5000 GBq/mumol) of 2-[123I]iodophenyl-metyrapone. A reaction in acetic acid at elevated temperatures proved superior to an exchange in aqueous solution with in-situ reduction of Cu2+. Even without Cu+ high radiochemical yields of > 80% were obtained, while addition of Cu+ provided the radiotracer with 95% radiochemical yield within 5 minutes in acetic acid.
authors.affiliation: Klinik und Poliklinik für Nuklearmedizin, Universitätsklinikum, Essen, FRG.
authors.forename: A
authors.initials: A
authors.lastname: Schirbel
authors.forename: H H
authors.initials: HH
authors.lastname: Coenen
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003300:Copper / Q000737:chemistry; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D008797:Metyrapone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: C093930:2-iodophenylmetyrapone; D007457:Iodine Radioisotopes; D003300:Copper; D008797:Metyrapone