Solid-Phase Synthesis of 2-[¹⁸F]Fluoropropionyl Peptides

The 2-[¹⁸F]fluoropropionic (2-[¹⁸F]FPA) acid is used as a prosthetic group for radiolabeling proteins and peptides for targeted imaging using positron emission tomography (PET). Radiolabeling of compounds with more than one acylable functional group can lead to complex mixtures of products; however, peptides can be labeled regioselectively on the solid phase. We investigated the use of a solid-phase approach for the preparation of 2-[¹⁸F]fluoropropionyl peptides. [¹⁸F]FPA was prepared and conjugated to the peptides attached to the solid phase support. The ¹⁸F-labeled peptides were obtained in 175 min with decay corrected yields of 10% (related to [¹⁸F]fluoride) and with a purity of 76−99% prior HPLC purification. The suitability of various coupling reagents and solid supports were tested for radiolabeling of several peptides of various lengths.