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Labeling of aliphatic carboxylic acids using [11C]carbon monoxide

Abstract

Here we present a protocol for labeling aliphatic carboxylic acids with the positron-emitting radionuclide 11C (t1/2 = 20.4 min) at the carboxyl position using [11C]carbon monoxide via photoinitiated free radical-mediated carbonylation. A solution of an alkyl iodide in a homogenous binary organic solvent–water mixture is introduced into a high-pressure photochemical reactor containing [11C]carbon monoxide. Then the reactor contents are pressurized to 40 MPa and irradiated with ultraviolet light for 6 min. The labeled product is purified using HPLC. All manipulations with radioactivity including the labeling synthesis are carried out on an automated Synthia system. In a typical case, 3.19 GBq of purified [1-11C]1,10-decanedicarboxylic acid (with a specific radioactivity of 188 GBq/μmol) can be obtained within 35 min after the end of a 10-μAh bombardment. Compared to previous labeling methods, this protocol is compatible with a wider range of functional groups, utilizes less-sensitive precursors, and is less subject to isotopic dilution.

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Figure 1
Figure 2
Figure 3: The Carbon Monoxide Synthia system for production and use of [11C]carbon monoxide in photoinitiated free radical-mediated carbonylation reactions.
Figure 4: Structures of labeled compounds.

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Acknowledgements

We thank T. Ferm for his skillful technical assistance. Financial support from the Swedish Research Council and Uppsala University Amersham Fund is gratefully acknowledged.

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Correspondence to Oleksiy Itsenko or Bengt Långström.

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Itsenko, O., Kihlberg, T. & Långström, B. Labeling of aliphatic carboxylic acids using [11C]carbon monoxide. Nat Protoc 1, 798–802 (2006). https://doi.org/10.1038/nprot.2006.112

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