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- Title
An improved radiosynthesis of O-(2-[<sup>18</sup>F]fluoroethyl)-O-( p-nitrophenyl)methylphosphonate: A first-in-class cholinesterase PET tracer.
- Authors
Neumann, Kiel D.; Thompson, Charles M.; Blecha, Joseph E.; Gerdes, John M.; VanBrocklin, Henry F.
- Abstract
O-(2-Fluoroethyl)-O-( p-nitrophenyl) methylphosphonate 1 is an organophosphate cholinesterase inhibitor that creates a phosphonyl-serine covalent adduct at the enzyme active site blocking cholinesterase activity in vivo. The corresponding radiolabeled O-(2-[18F]fluoroethyl)-O-(p-nitrophenyl) methylphosphonate, [ 18 F]1, has been previously prepared and found to be an excellent positron emission tomography imaging tracer for assessment of cholinesterases in live brain, peripheral tissues, and blood. However, the previously reported [ 18 F]1 tracer synthesis was slow even with microwave acceleration, required high-performance liquid chromatography separation of the tracer from impurities, and gave less optimal radiochemical yields. In this paper, we report a new synthetic approach to circumvent these shortcomings that is reliant on the facile reactivity of bis-(O,O-p-nitrophenyl) methylphosphonate, 2, with 2-fluoroethanol in the presence of DBU. The cold synthesis was successfully translated to provide a more robust radiosynthesis. Using this new strategy, the desired tracer, [ 18 F]1, was obtained in a non-decay-corrected radiochemical yield of 8 ± 2% (n = 7) in >99% radiochemical and >95% chemical purity with a specific activity of 3174 ± 345 Ci/mmol (EOS). This new facile radiosynthesis routinely affords highly pure quantities of [ 18 F]1, which will further enable tracer development of OP cholinesterase inhibitors and their evaluation in vivo.
- Subjects
PHOSPHONATES; ORGANIC synthesis; NITROPHENYL compounds; CHOLINESTERASES; POSITRON emission tomography; RADIOLABELING
- Publication
Journal of Labelled Compounds & Radiopharmaceuticals, 2017, Vol 60, Issue 7, p337
- ISSN
0362-4803
- Publication type
Article
- DOI
10.1002/jlcr.3511