Comparative study of specific activity of [11C]methyl iodide: A search for the source of carrier carbon

Iwata, Ren; Ido, Tatsuo; Ujiie, Akira; Takahashi, Toshihiro; Ishiwata, Kiichi; Hatano, Kentaro; Sugahara, Makoto

doi:10.1016/0883-2889(88)90084-6

Cited by 33 publications

(5 citation statements)

References 13 publications

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“…6,17,18 The specific activity obtained in this study was somewhat lower than the theoretical value (3.4 x 10 5 GBq/,umol), and this may have been due to contamination with carrier carbon-12 from the carbon dioxide in the target gas and methanol formed from the THF solution containing lithium aluminum hydride, as has been reported by some other groups.l 3,18-20 However, it has also been reported that there exists a lower limit at which it is difficult to overcome the effect of the carrier containing the final 11 C-labeled product synthesized via ["C]methyl iodide and that this limit is about 0.2 ,umol. 19 Since the total amount of carrier contained by [ 11 C]carfentanil produced in this study was about 0.25 ,amol, a shorter synthesis time and a higher initial 11 C radioactivity may be necessary to achieve a similar: Values are the mean (S.D.) for 4 animals.…”

Section: Preparation Of [ 11 C]carfentanilmentioning

confidence: 99%

Preparation and biodistribution in mice of [11C]carfentanil: A radiopharmaceutical for studying brain μ-opioid receptors by positron emission tomography

et al. 1992

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A potent mu-opioid agonist, [11C]carfentanil, was prepared by the methylation of carfentanil carboxylic acid with [11C]methyl iodide in order to study brain mu-opioid receptors by positron emission tomography. Synthesis (including purification) was completed within 25 min and the radiochemical yield was approximately 40%. The radiochemical purity of the product was more than 99% and its specific activity was 3.7-7.4 GBq/mumol. Biodistribution studies performed in mice after intravenous injection showed a high brain uptake and rapid blood clearance, so a high brain/blood ratio of 1.5-1.8 was found from 5 to 30 min. Regional cerebral distribution studies in the mouse showed a significantly higher uptake of [11C]carfentanil by the thalamus and striatum than by the cerebellum, with the radioactivity in the striatum disappearing more rapidly than that in the thalamus. Treatment with naloxone significantly reduced the uptake of [11C]carfentanil by the thalamus and striatum. These results indicate that [11C]carfentanil binds specifically to brain mu-opioid receptors.

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Section: Preparation Of [ 11 C]carfentanilmentioning

confidence: 99%

Preparation and biodistribution in mice of [11C]carfentanil: A radiopharmaceutical for studying brain μ-opioid receptors by positron emission tomography

et al. 1992

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“…This will lead to errors when quantifying target expression and may also lead to pharmacological side effects. To obtain high a SA for 11 CO 2 radiochemistry, adequate measures should be taken to avoid “contamination” with 12/13 CO 2 originating from the atmosphere, the cyclotron target, transfer tubing, reactors and reagents, as well as by shortening the reaction time (see also above) …”

Section: Prerequisites For the Translation Into Successful 11co2 Labementioning

confidence: 99%

“…One major example is the [ 11 C]CO 2 ‐based synthesis of [ 11 C]methyl iodide via the wet chemistry approach of applying highly CO 2 absorbing ethereal solutions of LiAlH 4 . It has been reported as one of the primary sources of non‐radioactive CO 2 to cause a decrease in the SA of carbon‐11 labelled products . Furthermore, low (around 20 GBq μmol −1 ) or highly varying SAs have been observed for radiotracers obtained by Grignard based C ‐ and N ‐ 11 C‐carboxylations .…”

Section: Prerequisites For the Translation Into Successful 11co2 Labementioning

confidence: 99%

Recent Progress in Metal Catalyzed Direct Carboxylation of Aryl Halides and Pseudo Halides Employing CO₂: Opportunities for ¹¹C Radiochemistry

et al. 2016

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Carbon dioxide (CO2) as a synthon in organic transformations is very useful, especially when combined with transition metal catalysts. CO2 insertion on carbon(Aryl)‐metal is are an elegant route to construct carbon–carbon bonds. A limited number of reports have been published to date on the direct conversion of aryl halides (or pseudo halides) to aryl carboxylic acids using transition metal catalysts. These reactions place great demand on the choice of catalyst, starting material, and reducing agent. However, these approaches could be of interest for the synthesis of a wide range of biologically active small molecules. Such transformations have already been applied for the synthesis of radiolabeled compounds for imaging with positron emission tomography (PET) using cyclotron produced [11C]CO2 and may be applicable to the production of a diverse range of PET tracers.

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“…Especially high specific activity is also required in the radio-synthesis of receptor agonists such as [ 11 C]carfentanil [9] and [ 11 C]alprazolam [10]. However, it has been difficult to achieve these levels of specific activity for 11 C-labeled compounds due to isotopic dilution by CO2 from the atmosphere and other contamination sources from chemicals, target material, and other substances in the course of synthesis [2,11]. [ 11 C]CH3I has been prepared mainly by reducing [ 11 C]CO 2 with LiAlH 4 [12,13], and has been also prepared recently by the reaction of [ 11 C]CH 4 with I2 vapor at high temperature [14,15].…”

Section: Introductionmentioning

confidence: 99%

Specific activity of [¹¹C]CO₂ generated in a N₂ gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy

Suzuki¹,

Yamazaki²,

Sasaki³

et al. 2000

Radiochimica Acta

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Specific activity / Irradiation effect / Sensitive analysis / 14 N(p,A) 11 C / [ 11 C]CO 2 Summary. Pure and O 2 -mixed nitrogen gases were irradiated by 18 MeV protons (14.2 MeV on target) and analyzed directly by a specially designed radio-GC system with a FID coupled to a methanyzer. Non-radioactive carbon, especially CO 2 was observed to be generated in the target chamber by irradiation and to decrease gradually with repeated irradiation. The amount of carbon was increased by the use of new materials for the front foil, transport line, and so on. Higher irradiation dose also increased the carrier carbon, where beam current affected carbon generation more strongly than irradiation time. The addition of oxygen gas to nitrogen gas also increased the amount of carrier carbon, nearly all of which was observed to be generated in the chemical form of CO 2. The ratio of [ 11 C]CO 2 to total C-11 was always low in a pure N 2 gas target and increased with higher irradiation dose, addition of oxygen gas and by changing some part of the irradiation system. The ratios of [ 11 C]CO 2 were 22.4 Ϯ 1.5 %, 77.8 Ϯ 7.1 % and 94.0 Ϯ 4.0 % in a pure N 2 gas, 9.8 ppm O 2 -mixed N 2 gas and 2000 ppm O 2-mixed N2 gas, respectively. The specific activity of [ 11 C]CO 2 increased by the addition of O 2 gas, but the effect of irradiation dose was not clear. Maximal specific activity of 610 Ϯ 150 GBq/µmol was obtained at the irradiation condition of 15 µA and 20 minutes in a 2000 ppm O 2 -mixed N 2 gas. The effect of proton energy on the CO 2 generation was also examined by degrading the proton energy with different thick energy absorbers. The amount of CO 2 generated in the target depended on the proton energy, i.e., larger amount of CO 2 generated with higher proton energy. Surprisingly, some amount of CO 2 (1.5 Ϯ 0.3 nmol) was still observed in the target, even in the condition that all the protons stopped in the front foil and did not irradiate the target gas.

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Comparative study of specific activity of [11C]methyl iodide: A search for the source of carrier carbon

Cited by 33 publications

References 13 publications

Preparation and biodistribution in mice of [11C]carfentanil: A radiopharmaceutical for studying brain μ-opioid receptors by positron emission tomography

Preparation and biodistribution in mice of [11C]carfentanil: A radiopharmaceutical for studying brain μ-opioid receptors by positron emission tomography

Recent Progress in Metal Catalyzed Direct Carboxylation of Aryl Halides and Pseudo Halides Employing CO₂: Opportunities for ¹¹C Radiochemistry

Specific activity of [¹¹C]CO₂ generated in a N₂ gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy

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Comparative study of specific activity of [11C]methyl iodide: A search for the source of carrier carbon

Cited by 33 publications

References 13 publications

Preparation and biodistribution in mice of [11C]carfentanil: A radiopharmaceutical for studying brain μ-opioid receptors by positron emission tomography

Preparation and biodistribution in mice of [11C]carfentanil: A radiopharmaceutical for studying brain μ-opioid receptors by positron emission tomography

Recent Progress in Metal Catalyzed Direct Carboxylation of Aryl Halides and Pseudo Halides Employing CO2: Opportunities for 11C Radiochemistry

Specific activity of [11C]CO2 generated in a N2 gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy

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Product

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Recent Progress in Metal Catalyzed Direct Carboxylation of Aryl Halides and Pseudo Halides Employing CO₂: Opportunities for ¹¹C Radiochemistry

Specific activity of [¹¹C]CO₂ generated in a N₂ gas target: effect of irradiation dose, irradiation history, oxygen content and beam energy