P.E.T. Radiopharmaceuticals Via Reductive Carboxylation

  • Siya Ram


Positron Emission Tomography (PET) is a powerful imaging diagnostic tool which uniquely provides qualitative and quantitative measurement of metabolic processes in vivo in normal and pathological tissue via application of appropriate radiotracers. Recently, there has been great interest in the development of fast and efficient new synthetic methodologies for positron emitting radiolabeled pharmaceuticals which can be used as tracers for P.E.T. studies. In the last decade, a variety of N-[11C] labeled radiopharmaceuticals1–2 have been synthesized via methylation of the appropriate desmethyl precursors with [11C]CH3I or reductive methylation with [11C]HCHO/NaBH3CN. In principle, both of these reagents [11C]CH3I or [11C]HCHO have been prepared from the more readily available [11C]CO2 via reduction to [11C]CH3OH, followed by iodination or oxidation as illustrated in Scheme-1. Further examination of the N-[11C] radiopharmaceuticals reveals that these bioactive molecules can be easily prepared directly from [11C] carbon dioxide under appropriate conditions. We have, therefore, investigated the use of [11C]CO2 as a radiolabeled precursor in the preparation of a variety of [11C] labeled compounds. In order to develop new synthetic methodologies for direct incorporation of [11C]CO2 into bioactive molecules, synthesis should be short and efficient and should be complete within three half-lives of the radioisotope. In general, literature synthetic procedures3 using [12C] or [14C]CO2 are not applicable for the synthesis of [11C] labeled radiopharmaceuticals because of the short 20.4 min half-life of the [11C] isotope. Hence, either extremely modified or entirely new procedures are desirable. A general reaction of [11C]CO2 with organometallics has been widely used for the preparation of [11C] carboxylic acid derivatives.


Positron Emission Tomography High Pressure Liquid Chromatography Bioactive Molecule Direct Incorporation Synthetic Methodology 
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Copyright information

© Springer Science+Business Media New York 1991

Authors and Affiliations

  • Siya Ram
    • 1
  1. 1.P.E.T. Facility/Nuclear Medicine Division Department of RadiologyDuke University Medical CenterDurhamUSA

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