Syntheses of F-18 labeled fluoroalkyltyrosine derivatives and their biological evaluation in rat bearing 9L tumor

We hereby report the synthesis of four fluorine-18 labeled tyrosine derivatives, 3-(2-[18F]fluoroethyl)tyrosine ([18F]1, [18F]ortho-FET), 3-(3-[18F]fluoropropyl)tyrosine ([18F]2, [18F]ortho-FPT) O-methyl-[3-(2-[18F]fluoroethyl)]tyrosine ([18F]3, [18F]MFET), and O-methyl-[3-(3-[18F]fluoropropyl)]tyrosine ([18F]4, [18F]MFPT). The fluorine-18 labeled tyrosine derivatives were prepared by the displacement reaction of the ethyl and propyl tosylates with K[18F]/K2.2.2 in acetonitrile under no-carrier-added (NCA) conditions, followed by hydrolysis with 4 N HCl. The biological properties of labeled compounds were evaluated in rats bearing 9L tumor after an intravenous injection and PET image was obtained. The tumor/blood and tumor/brain ratios were 2.06, 2.92 for [18F]1, 2.25, 4.05 for [18F]2, 2.88, 1.90 for [18F]3, and 2.00, 2.60 for [18F]4 at 60 min post injection, respectively. The PET image showed localized accumulation of PET tracers in 9L glioma of the rat.