Syntheses of [18F]5-fluoro-3-nitro-l-tyrosine

The detection of 3-nitro-l-tyrosine has been used as a biomarker of “reactive nitrogen species” in biological matrices and has been an ongoing challenge in analytical chemistry. In this work, fluorine-18 labelled 5-fluoro-3-nitro-l-tyrosine (FNT) was synthesized as a potential radiotracer to probe the biological fate of 3-nitro-l-tyrosine. The synthesis of [18F]FNT was carried out by reaction of [18F]3-fluoro-l-tyrosine with NaNO3 in TFA solvent for 5 min at 4 °C. The radiochemical yield (RCY) of [18F]FNT was 96±2% and [18F]3-fluoro-l-tyrosine, was 29±1%, relative to [18F]3-fluoro-l-tyrosine and [18F]F2, respectively. The syntheses of [18F]FNT were also accomplished by direct fluorination of 3-nitro-l-tyrosine with [18F]F2 and by nitration of l-tyrosine with NaNO3, followed by fluorination, in TFA (4 °C) or anhydrous HF (−65 °C) solvent. The latter two synthetic routes produced [18F]FNT in 13.5±1.5% RCY, within 1 h. Products were characterized by use of 1H, 13C and 19F NMR spectroscopy and mass spectrometry.