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A new procedure for labeling alkylbenzenes with [18F]fluoride
D R Hwang1, C S Dence, J L Gong
1Edward Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110.
International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes
|January 1, 1991
Summary
A novel method enables labeling alkylbenzenes with no-carrier-added [18F]fluoride. This technique facilitates the synthesis of [18F]fluorinated compounds for potential applications in radiopharmaceutical development.
Area of Science:
- Radiochemistry
- Organic Synthesis
- Nuclear Medicine
Background:
- Developing efficient methods for incorporating fluorine-18 (18F) into organic molecules is crucial for positron emission tomography (PET) imaging.
- Traditional methods for 18F labeling often require activating groups on aromatic rings, limiting their applicability.
Purpose of the Study:
- To report a new procedure for synthesizing no-carrier-added (nca) [18F]fluorinated alkylbenzenes.
- To enable the labeling of aromatic compounds lacking activating groups using [18F]fluoride.
Main Methods:
- A two-step procedure involving [18F]fluoride-for-nitro displacement on nitrophenones followed by reduction of the resulting [18F]fluorophenones.
- Utilized triethylsilane and trifluoroacetic acid for the reduction step to yield alkylfluorobenzenes.
Main Results:
- Successfully synthesized 18F-labeled alkylbenzenes in 1 hour with a 20% radiochemical yield.
- Applied the method to create 18F-labeled alkylating agents like 4-[18F]fluorophenethyl bromide and 4-[18F]fluorophenbutyl chloride.
- Investigated the labeling of amines using 4-[18F]fluorophenethyl bromide, observing low yields (<5%) due to competing styrene formation (>85%) under basic conditions.
Conclusions:
- The developed procedure offers a straightforward approach for labeling alkylbenzenes with 18F.
- While effective for alkylbenzene synthesis, challenges remain in directly labeling amines due to side reactions.