Radiosynthesis of 4-[¹⁸F]fluoromethyl-L-phenylalanine and [¹⁸F]FET via a same strategy and automated synthesis module

Currently there is still a need for more potent amino acid analogues as tumour imaging agents for peripheral tumour imaging with PET as it was recently reported that the success of O-(2'-[F-18]fluoroethyl)-L-tyrosine ([F-18]FET) is limited to brain, head and neck tumours. As the earlier described 2-Amino-3-(2-[F-18]fluoromethyl-phenyl)-propionic acid (2-[F-18]FMP) suffered from intramolecular-catalysed defluorination, we synthesized 2-Amino-3-(4-[F-18]fluoromethyl-phenyl)-propionic acid (4-[F-18]FMP) as an alternative for tumour imaging with PET. Radiosynthesis of 4-[F-18]FMP, based on Br for [F-18] aliphatic nucleophilic exchange, was performed with a customized modular Scintomics automatic synthesis hotbox(three) system in a high overall yield of 30% and with a radiochemical purity of \gt 99%. 4-[F-18]FMP was found to be stable in its radiopharmaceutical formulation, even at high radioactivity concentrations. Additionally, for a comparative study, [F-18]FET was synthesized using the same setup in 40% overall yield, with a radiochemical purity \gt 99%. The described automated radiosynthesis allows the production of two different amino acid analogues with minor alternations to the parameter settings of the automated system, rendering this unit versatile for both research and clinical practice.