Synthesis and characterization of the two enantiomers of a chiral sigma-1 receptor radioligand: (S)-(+)- and (R)-(-)-[18F]FBFP
Synthesis and characterization of the two enantiomers of a chiral sigma-1 receptor radioligand: (S)-(+)- and (R)-(-)-[18F]FBFP
Wang, T.; Zhang, Y.; Zhang, X.; Chen, L.; Zheng, M.-Q.; Zhang, J.; Brust, P.; Deuther-Conrad, W.; Huang, Y.; Jia, H.
Racemic [18F]FBFP ([18F]1) proved to be a potent σ1 receptor radiotracer with superior imaging properties. The pure enantiomers of unlabeled compounds (S)- and (R)-1 and the corresponding iodonium ylide precursors were synthesized and characterized. The two enantiomers (S)-1 and (R)-1 exhibited comparable high affinity for σ1 receptors and selectivity over σ2 receptors. The Ca2+ fluorescence assay indicated that (R)-1 behaved as an antagonist and (S)-1 as an agonist for σ1 receptors. The 18F-labeled enantiomers (S)- and (R)-[18F]1 were obtained in > 99% enantiomeric purity from the corresponding enantiopure iodonium ylide precursors with radiochemical yield of 24.4% ± 2.6% and molar activity of 86 – 214 GBq/μmol. In ICR mice both (S)- and (R)-[18F]1 displayed comparable high brain uptake, brain-to-blood ratio, in vivo stability and binding specificity in the brain and peripheral organs. In micro-positron emission tomography (PET) imaging studies in rats, (S)-[18F]1 exhibited faster clearance from the brain than (R)-[18F]1, indicating different brain kinetics of the two enantiomers. Both (S)- and (R)-[18F]1 warrant further evaluation in primates to translate a single enantiomer with more suitable kinetics for imaging the σ1 receptors in humans.
Keywords: σ1 receptor; Enantiomer; Radiotracer; Positron emission tomography; Fluorine-18
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Chinese Chemical Letters 33(2022)7, 3543-3548
Online First (2022) DOI: 10.1016/j.cclet.2022.03.099
Cited 6 times in Scopus
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