Synthesis and evaluation of 18F-labeled 4-nitrobenzyl derivatives for imaging tumor hypoxia with positron emission tomography: Comparison of 2-[18F]fluoroethyl carbonate and 2-[18F]fluoroethyl carbamate

Two 4-nitrobenzyl derivatives, 2-fluoroethyl 4-nitrobenzyl carbonate 1 and 4-nitrobenzyl N-2-fluoroethyl carbamate 2, were radiolabeled with F-18 and evaluated for imaging tumor hypoxia with positron emission tomography. Although good tumor uptake was observed for [F-18] 1 and [F-18] 2 (>2.5% ID/g at 3-h post-injection), the tracers cleared slowly from nontarget tissues (>1.5% ID/g) and exhibited extensive defluorination in vivo (>4.0% ID/g for bone). Therefore, [F-18] 1 and [F-18] 2 are not suitable for imaging tumor hypoxia due to suboptimal tumor-to-background contrasts. (C) 2015 Elsevier Ltd. All rights reserved.