<p>In the last few years click chemistry reactions, and in particular copper-catalyzed cycloadditions have been used extensively for the preparation of new bioconjugated molecules such as F-18-radiolabeled radiopharmaceuticals for positron emission tomography (PET). This study is focused on the synthesis of the Siemens imaging biomarker [F-18]RGD-K5. This cyclic peptide contains an amino acid sequence which is a well known binding motif for integrin alpha(v)beta(3) involved in cellular-adhesion to the extracellular matrix. We developed an improved "click" chemistry method using Cu(I)-Monophos as catalyst to conjugate [F-18]fluoropentyne to the RGD-azide precursor yielding [F-18]RGD-K5. A comparison is made with the registered Siemens method with respect to synthesis, purification and quality control. [F-18]RGD-K5 was obtained after 75 min overall synthesis time with an overall radiochemical yield of 35% (EOB). The radiochemical purity was >98% and the specific radioactivity was 100-200 GBq/mu mol at the EOS. (C) 2013 Elsevier Inc. All rights reserved.</p>
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