1986 Fiscal Year Final Research Report Summary
Design of Radiotracers Labeled with Short-Lived Nuclides as Brain Radiopharmaceuticals
| Project/Area Number |
59570440
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Radiation science
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| Research Institution | Kyushu University |
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Principal Investigator |
MAEDA MINORU Kyushu University, Faculty of Pharmaceutical Sciences, 薬学部, 助教授 (70101178)
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| Project Period (FY) |
1984 – 1986
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| Keywords | Iodine-131 / Solid-phase triazene reaction / Dimethylsulfonium salt / Fluoride ion / Bromofluorination; <^(11)C> -ethanolamine / 炭素-11フェニルエタノールアミン / 酵素法 |
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| Research Abstract |
The research has been aimed at the development of new radiopharmaceuticals with high specific activity for brain functional imaging, where the development of new reaction systems for preparing such radiotracers is essentially needed. No-carrieradded 2-(4-[ <^(131)I> ]iodophenyl)- and 8-[ <^(131)I> ]iodo-2-phenylpyrazolo[4,3-c]quinolin-3(5H)-one were prepared in isolated radiochemical yields of 11.6 and 5.4%, respectively, by acid decomposition of aryl triazenes in acetonitrile. A modified triazene method involving solid-phase decomposition reactions increased the yields to 15-35%. This modified procedure can be also applied to the high specific activity synthesis of other aromatic radiohalide compounds where difficulties occurs in obtaining satisfactory yields by decomposition of diazonium salt in an organic solvent. The utility of aromatic dimethylsulfonium group as a leaving group in nucleophilic substitution with fluoride ion has been investigated and this new fluorination gives an alternative method for preparing aromatic precursors for <^(18)F> radiopharmaceuticals. The recent preparation and successful use of <^(18)F> tetra-n-butylammonium fluoride led to also investigate the labeling reaction system consisting of this agent in conjunction with N-bromoimides for bromofluorination of double bonds and this method provides satisfactory yields of bromo-fluoride adducts. NCA [1- <^(11)C> ]phenylethanolamine was prepared by the oxynitrilase-catalyzed addition of [ <^(11)C> ]HCN to benzaldehyde followed by reduction of the [ <^(11)C> ]cyanohydrin. Radiochemical yields of 2-7% at end-of-synthesis were obtained in a synthesis time of 50-60 min. The enantiomeric composition was determined through its conversion to the MTPA diastereomers; the enantiomeric purity of the [ <^(11)C> ]phenylethanolamine produced via Co <Cl_2> -NaB <H_4> reduction was 60% e.e. while that prepared through boran-THF complex reduction was 80% e.e.
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