3.3.2. Radiosynthesis of [18F]**1**

No carrier added [18F]fluoride in 1.5 mL water was trapped on a Sep-Pak Accell Plus QMA Carbonate Plus light cartridge (Waters GmbH, Eschborn, Germany). The activity was eluted with 400 μL of an aqueous solution of potassium carbonate (K2CO3, 1.8 mg, 13 μmol) into a 4 mL V-shape vial prefilled with Kryptofix® 2.2.2 (K2.2.2, 11 mg, 29 μmol) in 1 mL ACN. The aqueous [18F]fluoride was azeotropically dried under vacuum and nitrogen flow within 7–10 min using a single mode microwave (75 W, at 50–60 ◦C, power cycling mode; Discover PETWave from CEM GmbH, Kamp-Lintfort, Germany) [60]. Two aliquots of ACN (2 × 1.0 mL) were added during the drying procedure and the final complex was obtained in a dried form. A solution of 1.0 mg of the nitro precursor **15** in 750 μL

DMSO was added, and the 18F-labeling was performed at 130 ◦C. To determine the radiochemical yields of the labeling process, samples were taken at different time points (5, 10, 15, and 20 min) and analyzed by radio-HPLC and radio-TLC.

After cooling to < 30 ◦C, the reaction mixture was diluted with 2.0 mL aqueous NH4HCO2 (adjusted to pH 4 with formic acid) and 2.0 mL MeOH/water (1:/1) and directly applied to an isocratic semi-preparative RP-HPLC for isolation of [18F]**1**. The collected radiotracer fraction was diluted with 40 mL water to perform final purification by sorption on a Sep-Pak® C18 light cartridge (Waters, GmbH, Eschborn, Germany) and successive elution with 1.3 mL of ethanol. The ethanolic solution was concentrated under a gentle argon stream at 70 ◦C to a final volume of 10–50 μL. Afterwards, the radiotracer was diluted in isotonic saline to obtain a final product containing 10% of EtOH (*v*/*v*).
