Two-step radiosynthesis of [¹⁸F]N-succinimidyl-4-fluorobenzoate ([¹⁸F]SFB)

The acylation reagent [¹⁸F]N-succinimidyl-4-fluorobenzoate (¹⁸F-SFB) has been prepared using a new two-step approach. The starting material p-[¹⁸F]fluorobenzaldehyde (¹⁸F-FBA) was obtained by an improved radiosynthesis with a decay-corrected radiochemical yield of 66±6 % (n = 3). Reaction of ¹⁸F-FBA with (diacetoxyiodine)benzene and N-hydroxysuccinimide and preparative HPLC purification furnished ¹⁸F-SFB in an r.c.y. of 49±6 % (n = 3), based on the starting radioactivity of ¹⁸F-FBA. The radiochemical purity of ¹⁸F-SFB was >99%. Alternatively, purification by solid phase extraction gave ¹⁸F-SFB with an r.c.y. of 77±9% (n = 4) and a radiochemical purity of 89±5% (n = 4). This radiochemical synthesis only used non-aqueous solvents, which simplifies the method and facilitates subsequent applications of ¹⁸F-SFB.