- Cross-coupling of [11C]methyllithium for 11C-labelled PET tracer synthesis
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The cross-coupling of aryl bromides with [11C]CH3Li for the labelling of a variety of tracers for positron emission tomography (PET) is presented. The radiolabelled products were obtained in excellent yields, at rt and after short reaction times (3-5 min) compatible with the half-life of 11C (20.4 min). The automation of the protocol on a synthesis module is investigated, representing an important step towards a fast method for the synthesis of 11C-labelled compounds for PET imaging. This journal is
- Helbert, Hugo,Antunes, Ines Farinha,Luurtsema, Gert,Szymanski, Wiktor,Feringa, Ben L.,Elsinga, Philip H.
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supporting information
p. 203 - 206
(2021/01/13)
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- Aromatic radiofluorination and biological evaluation of 2-aryl-6-[ 18F]fluorobenzothiazoles as a potential positron emission tomography imaging probe for β-amyloid plaques
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To develop agents for radionuclide imaging Aβ plaques in vivo, we prepared three fluorine-substituted analogs of arylbenzothiazole class; compound 2 has a high affinity for Aβ (Ki = 5.5 nM) and the specific binding to Aβ in fluorescent staining. In preparation for the synthesis of these arylbenzothiazole analogs in radiolabeled form as an Aβ plaques-specific positron emission tomography (PET) imaging probe, we investigated synthetic route suitable for its labeling with the short-lived PET radionuclide fluorine-18 (t1/2 = 110 min) and diaryliodonium tosylate precursors (12, 13a-e and 14). 2-Aryl-6-[18F]fluorobenzothiazoles ([18F]1-3) were synthesized in efficiently short reaction times (40-60 min) with high radiochemical yields (19-40%), purities (>95%) and specific activities (85-118 GBq/μmol). Tissue distribution studies showed that high radioactivity of [18F]2 accumulated in the brain with rapid clearance in healthy mice. Radioactive metabolites were analyzed in brain samples of mice and corresponded to 81% of parent remained by 30 min after a tail-vein injection. These results suggest that [18F]2 is a promising probe for evaluation of Aβ plaques imaging in brain using PET.
- Lee, Byung Chul,Kim, Ji Sun,Kim, Bom Sahn,Son, Ji Yeon,Hong, Soo Kyung,Park, Hyun Soo,Moon, Byung Seok,Jung, Jae Ho,Jeong, Jae Min,Kim, Sang Eun
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experimental part
p. 2980 - 2990
(2011/06/19)
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- Synthesis and evaluation of 11C-labeled 6-substituted 2-arylbenzothiazoles as amyloid imaging agents.
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The synthesis and evaluation of a series of neutral analogues of thioflavin-T (termed BTA's) with high affinities for aggregated amyloid and a wide range of lipophilicities are reported. Radiolabeling with high specific activity [(11)C]methyl iodide provided derivatives for in vivo evaluation. Brain entry in control mice and baboons was high for nearly all of the analogues at early times after injection, but the clearance rate of radioactivity from brain tissue varied by more than 1 order of magnitude. Upon the basis of its rapid clearance from normal mouse and baboon brain tissues, [N-methyl-(11)C]2-(4'-methylaminophenyl)-6-hydroxybenzothiazole (or [(11)C]6-OH-BTA-1) was selected as the lead compound for further evaluation. The radiolabeled metabolites of [(11)C]6-OH-BTA-1 were polar and did not enter brain. The binding affinities of [N-methyl-(3)H]6-OH-BTA-1 for homogenates of postmortem AD frontal cortex and synthetic Abeta(1-40) fibrils were similar (K(d) = 1.4 nM and 4.7 nM, respectively), but the ligand-to-Abeta peptide binding stoichiometry was approximately 400-fold higher for AD brain than Abeta(1-40) fibrils. Staining of AD frontal cortex tissue sections with 6-OH-BTA-1 indicated the selective binding of the compound to amyloid plaques and cerebrovascular amyloid. The encouraging in vitro and in vivo properties of [(11)C]6-OH-BTA-1 support the choice of this derivative for further evaluation in human subject studies of brain Abeta deposition.
- Mathis, Chester A,Wang, Yanming,Holt, Daniel P,Huang, Guo-Feng,Debnath, Manik L,Klunk, William E
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p. 2740 - 2754
(2007/10/03)
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- Radioiodinated styrylbenzenes and thioflavins as probes for amyloid aggregates
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We report for the first time that small molecule-based radiodiodinated ligands, showing selective binding to Aβ aggregates, cross the intact blood-brain barrier by simple diffusion. Four novel ligands showing preferential labeling of amyloid aggregates of Aβ(1-40) and Aβ(1-42) peptides, commonly associated with plaques in the brain of people with Alzheimer's disease (AD), were developed. Two 125I-labeled styrylbenzenes, (E,E)-1-iodo-2,5-bis(3-hydroxvcarbonyl-4-hydroxy)-styrylbenzene, 12 (ISB), and (E,E)-1-iodo-2,5-bis(3-hydroxycarbonyl-4-methoxy)styrylbenzene, 13 (IMSB), and two 125I-labeled thioflavins, 2-[4′-(dimethylamino)phenyl]-6-iodobenzothiazole, 18a (TZDM), and 2-[4′-(4″-methylpiperazin-1-yl)phenyl]-6-iodobenzothiazole, 18b (TZPI), were prepared at a high specific activity (2200 Ci/mmol). In vitro binding studies of these ligands showed excellent binding affinities with Kd values of 0.08, 0.13, 0.06, and 0.13 nM for aggregates of Aβ(1-40) and 0.15, 0.73, 0.14, and 0.15 nM for aggregates of Aβ(1-42), respectively. Interestingly, under a competitive-binding assaying condition, different binding sites on Aβ(1-40) and Aβ(1-42) aggregates, which are mutually exclusive, were observed for styrylbenzenes and thioflavins. Autoradiography studies of postmortem brain sections of a patient with Down's syndrome known to contain primarily Aβ(1-42) aggregates in the brain showed that both [125I]18a and [125I]18b labeled these brain sections, but [125I] 13, selective for Aβ(1-40) aggregates, exhibited very low labeling of the comparable brain section. Biodistribution studies in normal mice after an iv injection showed that [125I]18a and [125I]18b exhibited excellent brain uptake and retention, the levels of which were much higher than those of [125I]12 and [125I]13. These findings strongly suggest that the new radioiodinated ligands, [125I]12 (ISB), [125I]13 (IMSB), [125I]18a (TZDM), and [125I]18b (TZPI), may be useful as biomarkers for studying Aβ(1-40) as well as Aβ(1-42) aggregates of amyloidogenesis in AD patients.
- Zhuang,Kung,Hou,Skovronsky,Gur,Pl?ssl,Trojanowski,Lee,Kung
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p. 1905 - 1914
(2007/10/03)
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