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

Abstract

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