Synthesis and bioevaluation of [18F]4-fluoro-m- hydroxyphenethylguanidine ([18F]4F-MHPG): A novel radiotracer for quantitative PET studies of cardiac sympathetic innervation
A new cardiac sympathetic nerve imaging agent, [18F]4-fluoro-m- hydroxyphenethylguanidine ([18F]4F-MHPG), was synthesized and evaluated. The radiosynthetic intermediate [18F]4-fluoro-m-tyramine ([18F]4F-MTA) was prepared and then sequentially reacted with cyanogen bromide and NH4Br/NH4OH to afford [ 18F]4F-MHPG. Initial bioevaluations of [18F]4F-MHPG (biodistribution studies in rats and kinetic studies in the isolated rat heart) were similar to results previously reported for the carbon-11 labeled analog [11C]4F-MHPG. The neuronal uptake rate of [18F]4F-MHPG into the isolated rat heart was 0.68 ml/min/g wet and its retention time in sympathetic neurons was very long (T1/2 >13 h). A PET imaging study in a nonhuman primate with [18F]4F-MHPG provided high quality images of the heart, with heart-to-blood ratios at 80-90 min after injection of 5-to-1. These initial kinetic and imaging studies of [18F]4F-MHPG suggest that this radiotracer may allow for more accurate quantification of regional cardiac sympathetic nerve density than is currently possible with existing neuronal imaging agents.
Jang, Keun Sam,Jung, Yong-Woon,Sherman, Phillip S.,Quesada, Carole A.,Gu, Guie,Raffel, David M.
p. 1612 - 1616
(2013/04/10)
Labeling of benzodioxin piperazines with fluorine-18 as prospective radioligands for selective imaging of dopamine D4 receptors
The D4 receptor is of high interest for research and clinical application but puts high demands on appropriate radioligands to be useful tools for investigation. Search for adequate radioligands suitable for in vivo imaging is therefore still in progress. The potential neuroleptic drug 6-(4-[4-fluorobenzyl]piperazin-1-yl)benzodioxin shows high affinity and selectivity to the D4 receptor. Derivatization of this lead structure by adding hydrophilic moieties was carried out in order to lower its lipophilicity what led to three new putative dopamine receptor D4 ligands. A comprehensive description of the syntheses of standard compounds and corresponding labeling precursors is given which were obtained in satisfactory yields. Furthermore, the radiosyntheses by direct 18F-labeling and build-up synthesis were compared. All derivatives of 6-(4-[4-fluorobenzyl]- piperazin-1-yl)benzodioxin were successfully synthesized in 18F- labeled form with radiochemical yields of 9-35% and molar activities of 30-60 GBq/μmol using one-pot procedures. 2013 John Wiley & Sons, Ltd. Derivatives of the lead structure 6-(4-[4-fluorobenzyl]-piperazine-1-yl) benzodioxin were successfully synthesized, labeled via direct 18F-substitution or build-up synthesis leading to new putative radioligands for imaging of the dopamine D4 receptor. Reductive amination proved as the method of choice for preparation of substituted benzyl-derivatives of piperazine as precursors and standards, and also superior for build-up radiofluorination (RCY = 9 - 35;%) in comparison to direct 18F- labeling (RCY = 1 - 5;%).
Kuegler, Fabian,Ermert, Johannes,Coenen, Heinz H.
p. 609 - 618
(2013/12/04)
Synthesis of high-specific-radioactivity 4- and 6-[18F]fluorometaraminol- PET tracers for the adrenergic nervous system of the heart
Fluorine-18 (t12:109.8min)-labeled analogues of metaraminol, 4-[18F]FMR ((1R,2S)-2-amino-1-(4-[18F]fluoro-3-hydroxy phenyl)-1-propanol) and 6-[18F]FMR ((1R,2S)-2-amino-1-(2-[18F]fluoro-5-hydroxyphenyl)-1-propanol), were synthesized as new positron-emission-tomography (PET) tracers for mapping cardiac adrenergic nerve terminals. Copyright