Scheme 6. cGMP Synthesis of [¹⁸F]5-Fluorouracil (>10 mCi) for Use in Human PET Imaging.

Based on decay-corrected measurement of trapped activity on a microcartridge, relative to initial [¹⁸F]fluoride in [¹⁸O]water.

Three elutions were applied, with 0.5 μmol of K₃PO₄ and 3.0 μmol of 18-crown-6 ([18c6]) in 6.2 μL of MeCN/H₂O (4/1, v/v) per elution.

Based on decay-corrected measurement of eluted activity relative to trapped activity.

Yield (not decay corrected) based on [¹⁸F]fluoride (range: 7–14 mCi) in 2.4 mL of water at the start of synthesis. Starting from 1.7 Ci of [¹⁸F]fluoride, the yield (not decay corrected) was 79%.

SPE: solid phase extraction; see Supporting Information for full purification details.

Isolated yield (not decay corrected) is based on activity of [¹⁸F]fluoride (range: 1.4–1.8 Ci) in [¹⁸O]water at the start of synthesis.