- An updated synthesis of N1′-([11C]methyl)naltrindole for positron emission tomography imaging of the delta opioid receptor
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A new method for the synthesis of the highly selective delta opioid receptor (DOR) antagonist radiotracer N1′-([11C]methyl)naltrindole ([11C]MeNTI) is described. The original synthesis required hydrogenation of a benzyl protecting group after 11C-labeling, which is challenging in modern radiochemistry laboratories that tend to be heavily automated and operate according to current good manufacturing practice. To address this challenge, we describe development of a novel MeNTI precursor bearing a methoxymethyl acetal (MOM) protecting group, which is easily removed with HCl, and employ it in an updated synthesis of [11C]MeNTI. The new synthesis is fully automated and validated for clinical use. The total synthesis time is 45 min and provides [11C]MeNTI in good activity yield (49 ± 8 mCi), molar activity (3,926 ± 326 Ci/mmol) and radiochemical purity (97% ± 2%).
- Kaur, Tanpreet,Brooks, Allen F.,Hockley, Brian G.,Torres, Jovany,Henderson, Bradford D.,Scott, Peter J.H.,Shao, Xia
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p. 187 - 193
(2020/12/17)
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- Synthesis of tritiated N1'-alkyl derivatives of the delta opioid receptor ligand naltrindole
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Tritiated N1'-methyl and N1'-ethyl analogues of naltrindole (NTI) have been synthesized for evaluation as radioligands for studies of delta opioid receptors. The two N1'-alkyl-5',7'-dibromoNTI precursors for radiolabeling were prepared by base-promoted alkylation of 2,4-dibromophenylhydrazine with either iodomethane or iodoethane followed by condensation with naltrexone using the Fischer indole synthesis. Catalytic debromotritiation followed by HPLC purification afforded [3H]MeNTI (17.3 Ci/mmol) and [3H]EtNTI (22.5 Ci/mmol) with high chemical and radiochemical purities (≤ 99.8%).
- Lever, John R.,Johnson, Suzanne M.
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p. 115 - 122
(2007/10/03)
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- SYNTHESIS OF N1'-(METHYL)NALTRINDOLE (MeNTI): A RADIOLIGAND FOR POSITRON EMISSION TOMOGRAPHIC STUDIES OF DELTA OPIOID RECEPTORS
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A delta opioid receptor antagonist, N1'-methylnaltrindole (MeNTI), has been labeled with carbon-11.The precursor for radiolabeling was prepared in 71percent yield by benzylation of the phenolic moiety of naltrindole.Alkylation of the indole nitrogen using
- Lever, John R.,Kinter, Chris M.,Ravert, Hayden T.,Musachio, John L.,Mathews, William B.,Dannals, Robert F.
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p. 137 - 146
(2007/10/02)
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