Synthesis and application of 4-[F-18] fluorobenzylamine: A versatile building block for the preparation of PET radiotracers

A novel synthesis of 4-[F-18]fluorobenzylamine ([F-18]FBA) by means of transition metal-assisted sodium borohydride reduction of 4-[F-18]fluorobenzonitrile ([F-18]FBN) is described. This approach could successfully be extended to borohydride exchange resin (BER) enabling a viable option for use in automated syntheses. [F-18]FBA was used for the synthesis of 4-[F-18]fluorobenzylamine-based thiol group-reactive prosthetic groups 4-[F-18]fluorobenzyl-2-bromoacetamide ([F-18]FBBA) and 4-[F-18]fluorobenzylamidopropionyl maleimide ([F-18]FBAPM). [F-18]FBBA and [F-18]FBAPM were obtained in radiochemical yields of 75% and 55%, respectively. Feasibility of using [F-18]FBAPM as novel prosthetic group for peptide and protein labelling was demonstrated with cysteine-containing tripeptide glutathione (GSH). [F-18]FBBA was used for labelling of a fully phosphorothioated 20mer oligodesoxynucleotide (ODN).