Synthesis of N1′-([18F]fluoroethyl)naltrindole ([18F]FEtNTI): a radioligand for positron emission tomographic studies of delta opioid receptors

• Published in: Journal of labelled compounds & radiopharmaceuticals Vol. 42; no. 1; pp. 43 - 54
• Main Authors: Mathews, William B., Kinter, Chris M., Palma, James, Daniels, Robert V., Ravert, Hayden T., Dannals, Robert F., Lever, John R.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.1999; Wiley
• Subjects: Biochemical Research Methods; Biochemistry & Molecular Biology; Biological and medical sciences; Chemistry; Chemistry, Analytical; Chemistry, Medicinal; Contrast media. Radiopharmaceuticals; delta opioid receptor; fluorine-18; Life Sciences & Biomedicine; Medical sciences; naltrindole; Pharmacology & Pharmacy; Pharmacology. Drug treatments; Physical Sciences; positron emission tomography; Science & Technology; naltrindole; fluorine-18; delta opioid receptor; positron emission tomography; N1'-(METHYL)NALTRINDOLE; BRAIN; Fluorine Isotopes; Morphine derivatives; Fluorine 18; Radiolabelling; Ligand; Scintigraphic agent; Polycyclic compound; Aromatic compound; Naltrexone; δ Opioid receptor; Chemical synthesis; Oxygen nitrogen heterocycle
• ISSN: 0362-4803; 1099-1344
• DOI: 10.1002/(SICI)1099-1344(199901)42:1<43::AID-JLCR165>3.0.CO;2-2

N1′‐([18F]fluoroethyl)naltrindole ([18F]FEtNTI), a novel analog of the delta opioid receptor antagonist naltrindole (NTI), has been prepared for evaluation as a radioligand for use in positron emission tomography. The precursor for radiolabeling was obtained in four steps from naltrexone hydrochloride with an overall yield of 47%. Nucleophilic displacement of a tosylate leaving group by [18F]fluoride, followed by hydrogenolysis (H2, 10% Pd/C) of a benzyl protecting group on the phenolic moiety, gave [18F]FEtNTI. The average (n=5) time for radiosynthesis, HPLC purification, and formulation was 77 min from end of bombardment. [18F]FEtNTI of high radiochemical purity was obtained with an average specific activity of 846 mCi/μmol at end of synthesis, and an average radiochemical yield of 10% (not corrected for decay). Copyright © 1999 John Wiley & Sons, Ltd.