Synthesis and in vitro evaluation of 18F labeled tyrosine derivatives as potential positron emission tomography (PET) imaging agents

Three new 18F labeled fluoroalkyl tyrosine derivatives, O-(2-[18F]fluoroethyl)-α-methyltyrosine (FEMT, [18F]2), O-(2-[18F]fluoroethyl)-2-l-azatyrosine (FEAT, [18F]3), O-(2-[18F]fluoroethyl)-l-tyrosineamide (FETA, [18F]4) have been synthesized and radiofluorinated with 5-34% decay-corrected yield. In vitro studies were carried out in U-138 MG human glioblastoma. Cellular uptake of new tracers was compared to clinically utilized imaging agent O-(2-[18F]fluoroethyl)-l-tyrosine (FET, [18F]1). The uptake of tracers followed the order of FET ([18F]1) > FEAT([18F]3) > FEMT ([18F]2) ≈ FETA ([18F]4).