title: An evaluation of a high-pressure (11)CO carbonylation apparatus.
abstract: [(11)C]Carbon monoxide ((11)CO) is a versatile building block for the synthesis of Positron Emission Tomography (PET) radioligands. However, the difficulty of trapping (11)CO in a small solvent volume has limited its utility. We here report an evaluation of a simple, fully automated high-pressure synthesizer prototype for the use in (11)C-carbonylation reactions. [(11)C]Carbon monoxide was easily prepared by online reduction of [(11)C]carbon dioxide using either Mo(s) or Zn(s) as the reducing agent. The conversion yield of (11)CO was >99% when zinc was used as the reducing agent, and the corresponding value for Mo was approximately 71%. When the Zn or Mo column was constantly kept under inert atmosphere, no significant decrease in reducing properties was observed for more than 100 (11)CO productions. However, in our hands, Mo reductant was much easier to service. A total of nine functional groups were successfully radiolabeled using the (11)CO synthesizer prototype. All measured radiochemical yields exceeded 37%, and the (11)CO trapping efficiency was generally above 90%, except for the Suzuki coupling where the trapping efficiency was 80%. This high-pressure synthesizer using [(11)C]carbon monoxide as the labeling precursor is easy to operate allowing for (11)C-carbonylation reactions to be performed in a high yield and in a routinely fashion.
authors.affiliation: Centre for Psychiatric Research and Education, Department of Clinical Neuroscience, Karolinska Institutet, S-171 76, Stockholm, Sweden.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Dahl
authors.forename: Oleksiy
authors.initials: O
authors.lastname: Itsenko
authors.forename: Obaidur
authors.initials: O
authors.lastname: Rahman
authors.forename: Johan
authors.initials: J
authors.lastname: Ulin
authors.forename: Carl-Olof
authors.initials: CO
authors.lastname: Sjöberg
authors.forename: Peter
authors.initials: P
authors.lastname: Sandblom
authors.forename: Lars-Anders
authors.initials: LA
authors.lastname: Larsson
authors.forename: Magnus
authors.initials: M
authors.lastname: Schou
authors.forename: Christer
authors.initials: C
authors.lastname: Halldin
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry; D002248:Carbon Monoxide / Q000737:chemistry; D002250:Carbon Radioisotopes / Q000737:chemistry*; D060326:Chemistry Techniques, Synthetic / Q000295:instrumentation*; D008982:Molybdenum / Q000737:chemistry; D010084:Oxidation-Reduction; D011312:Pressure; D011854:Radiochemistry / Q000295:instrumentation*; D019275:Radiopharmaceuticals / Q000138:chemical synthesis*; D015032:Zinc / Q000737:chemistry
chemical_list: D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D002245:Carbon Dioxide; D002248:Carbon Monoxide; D008982:Molybdenum; D015032:Zinc
keywords: carbon-11; carbonylation; isotopic labeling; prototype; radiochemistry