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Efficient preparation of [11C]CH3Br for the labeling of [11C]CH3-containing tracers in positron emission tomography clinical practice.
MedLine Citation:
PMID:  21519304     Owner:  NLM     Status:  In-Data-Review    
Abstract/OtherAbstract:
BACKGROUND AND AIM: [C]methyl iodide ([C]CH3I) is the most extensively used methylation agent for the preparation of a majority of C-labeled positron emission tomography (PET) radiotracers, which is commonly produced by the wet method and the gas-phase method. On account of the complexity of the gas-phase method, a simple automated synthesis of [C]methyl bromide ([C]CH3Br) as an analog of [C]CH3I is derived by the wet method in this study. Radiosynthesis of L-[S-methyl-C]methionine (MET), L-[S-methyl-C]cysteine (MCYS), [N-methyl-C]choline (CH), [C]methyl triflate ([C]CH3OSO2CF3), and [C]-2-β-carbomethoxy-3-β-(4-fluorophenyl)-tropane (CFT) by methylation reaction with [C]CH3Br, and PET imaging of patients are also described.
METHODS: The preparation of [C]CH3Br by a one-pot wet method involved the following steps: reduction of [C]carbon dioxide with lithium aluminium hydride (LiAlH4) solution, treatment with hydrobromic acid, and distillation of [C]CH3Br under continuous nitrogen flow. [C]methylation of L-homocysteine thiolactone hydrochloride, L-cysteine, 2-dimethylaminoethanol, silver triflate, and nor-β-CFT as precursors with [C]CH3Br and purification with Sep-Pak cartridges gave MET, MCYS, CH, [C]CH3OSO2CF3, and CFT, respectively. In addition, PET imaging of brain cancer and Parkinson's disease was carried out.
RESULTS: The uncorrected radiochemical yield of [C]CH3Br was (37.8±2.5%) based on [C]carbon dioxide within a total synthesis time of 10 min and the radiochemical purity of [C]CH3Br was greater than 95%. The uncorrected yields of MET, MCYS, CH, [C]CH3OSO2CF3, and CFT were 70.1±0.5%, 70.2±2.3%, 60.3±1.8%, 95.1±2.2%, and 60.1±1.5% (from [C]CH3OSO2CF3) within a total synthesis time of 2, 2, 5, 1, and 8 min, respectively. The radiochemical purity of MET, MCYS, CH, [C]CH3OSO2CF3, and CFT was more than 95%. Good PET images in the patients are obtained.
CONCLUSION: Automated synthesis of [C]CH3Br can be done by the wet method on the commercial [C]CH3I synthesizer. [C]CH3Br can be used for a [C]methylation reaction to produce C-labeled tracers for clinical PET imaging.
Authors:
Ganghua Tang; Xiaolan Tang; Huaifu Deng; Hongliang Wang; Fuhua Wen; Chang Yi; Kening Wu
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Nuclear medicine communications     Volume:  32     ISSN:  1473-5628     ISO Abbreviation:  Nucl Med Commun     Publication Date:  2011 Jun 
Date Detail:
Created Date:  2011-04-26     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8201017     Medline TA:  Nucl Med Commun     Country:  England    
Other Details:
Languages:  eng     Pagination:  466-74     Citation Subset:  IM    
Affiliation:
aPET-CT Center, Department of Nuclear Medicine, The First Affiliated Hospital, Sun Yat-Sen University bCollege of Science, South China Agricultural University, Guangzhou, China.
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