Facile synthesis of N‐succinimidyl 4‐[18F]fluorobenzoate ([18F]SFB) for protein labeling

An efficient preparation of N‐succinimidyl 4‐[¹⁸F]fluorobenzoate ([¹⁸F]SFB) based on a convenient three‐step, one‐pot procedure is described. [¹⁸F]Fluorination of the precursor ethyl 4‐(trimethylammonium triflate)benzoate gave ethyl 4‐[¹⁸F]fluorobenzoate. Saponification of the ethyl 4‐[¹⁸F]fluorobenzoate with aqueous tetrapropylammonium hydroxide yielded the corresponding 4‐[¹⁸F]fluorobenzoate salt ([¹⁸F]FBA), which was then treated with N,N,N,N′‐tetramethyl‐O‐(N‐succinimidyl)uronium hexafluorophosphate. The purified [¹⁸F]SFB was used for the labeling of Avastin^? (Bevacizumab) through [¹⁸F]fluorobenzoylation of the Avastin's α‐amino groups. The decay‐corrected radiochemical yields of [¹⁸F]SFB were as high as 44% (based on [¹⁸F]fluoride (n=10) with a synthesis time of less than 60 min. [¹⁸F]Avastin was produced in decay‐corrected radiochemical yields of up to 42% (n=5) within 30 min (based on [¹⁸F]SFB). The radiochemical purities of [¹⁸F]SFB and [¹⁸F]Avastin were greater than 95%. Copyright © 2008 John Wiley & Sons, Ltd.