"Hydrous ¹⁸F-fluoroethylation" - Leaving off the azeotropic drying.

Area of Science:

• Radiochemistry
• Organic synthesis
• Nuclear medicine

Background:

• Conventional ¹⁸F-fluoroethylation methods often involve azeotropic drying, which can lead to fluoride loss and extended reaction times.
• Optimizing radiolabeling efficiency is crucial for developing novel PET imaging agents.

Purpose of the Study:

• To develop a simplified and efficient method for ¹⁸F-fluoroethylation by omitting the azeotropic drying step.
• To evaluate the performance of the new method using various COX-2 inhibitors as precursors.

Main Methods:

• Elution of a [¹⁸F]fluoride loaded QMA column with a K₂CO₃/K₂₂₂/acetonitrile solution containing 2-3% water directly to the precursor.
• Formation of the labeling agent 2-[¹⁸F]fluoroethyl tosylate ([¹⁸F]FETs) in situ.
• Application of the method to the ¹⁸F-fluoroethylation of three different COX-2 inhibitors.

Main Results:

• The hydrous ¹⁸F-fluoroethylation yielded 76-96% non-isolated radiochemical yield of [¹⁸F]FETs.
• Isolated radiochemical yields of final radiotracers were increased fivefold compared to conventional methods.
• The method demonstrated minimal loss of [¹⁸F]fluoride and significantly shortened overall reaction time.

Conclusions:

• The developed "hydrous ¹⁸F-fluoroethylation" offers a more efficient and streamlined approach for synthesizing ¹⁸F-labeled compounds.
• This simplified method improves radiochemical yields and reduces reaction times, making it advantageous for PET tracer development.