• Journal of Radiopharmaceuticals and Molecular Probes
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• v.3 no.1
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• pp.44-51
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• 2017

Herein we report an efficient radiolabeling method based on a rapid condensation reaction between N-terminal cysteine and 2-cyanobenzothiazole (CBT). Radioiodination of 2-cyano-6-hydroxybenzothiazole 2 was carried out using chloramine-T to give $^{125}I$-labeled CBT ([$^{125}I$]1) with a high radiochemical yield ($90{\pm}6%$ isolated yield, n=3) and radiochemical purity (>99%). To evaluate the radiolabeling efficiency of $^{125}I$-labeled CBT, model compounds, L-cysteine and N-terminal cysteine conjugated cRGD peptide were reacted with [$^{125}I$]1 under mild conditions. The radiolabeling reactions rapidly provided the $^{125}I$-labeled products [$^{125}I$]5 and [$^{125}I$]6 with excellent radiochemical yields and radiochemical purity. Therefore, we demonstrate that [$^{125}I$]1 will be a useful prosthetic group for radioactive iodine labeling of N-terminal cysteine bearing biomolecules.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.7 no.2
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• pp.153-159
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• 2021

This article provides an efficient ¹⁸F-labeling protocol based on a rapid condensation reaction between 2-cyanobenzothiazole (CBT) and N-terminal cysteine-containing biomolecules. The ¹⁸F-labeled CBT (¹⁸F-1) was prepared by radiofluorination of the tosylated precursor 4 with 18-crown-6/K+/[¹⁸F]F- complex. Using the purified ¹⁸F-1, ¹⁸F-labeled peptide (¹⁸F-7) and protein (¹⁸F-8) could be synthesized efficiently under mild conditions. This strategy would provide a convenient approach for rapid and site-specific ¹⁸F-labeling of various peptides and proteins for in vivo imaging and biomedical applications.