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

William B. Mathews, Chris M. Kinter, James Palma, Robert V. Daniels, Hayden T. Ravert, Robert F. Dannals, John R. Lever

Research output: Contribution to journalArticlepeer-review


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).

Original languageEnglish (US)
Pages (from-to)43-54
Number of pages12
JournalJournal of Labelled Compounds and Radiopharmaceuticals
Issue number1
StatePublished - Jan 1 1999


  • Delta opioid receptor
  • Fluorine-18
  • Naltrindole
  • Positron emission tomography

ASJC Scopus subject areas

  • Analytical Chemistry
  • Biochemistry
  • Radiology Nuclear Medicine and imaging
  • Drug Discovery
  • Spectroscopy
  • Organic Chemistry

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