NCA nucleophilic radiofluorination on substituted benzaldehydes for the preparation of [18F]fluorinated aromatic amino acids

Nucleophilic aromatic substitution is a challenging task in radiochemistry. Therefore, a thorough evaluation and optimisation of this step is needed to provide a satisfactory tool for the routine preparation of [18F]fluorinated aromatic amino acids. Two methods, already proposed elsewhere, were evaluated and improved. The yields for the radiofluorination were increased whereas activity loss during solid phase extraction was observed. Radiochemical yields for the two methods were 92.7±5.5% (method 1) and 92.1±12.3% (method 2) for conversion and 11.1±2.8% (method 1) and 34.8±0.6% (method 2) for purification, respectively. In total, we demonstrate an optimised method for the preparation of this important class of [18F]fluorinated synthons for PET.