title: A novel 2-cyanobenzothiazole-based (18)F prosthetic group for conjugation to 1,2-aminothiol-bearing targeting vectors.
abstract: In a bid to find an efficient means to radiolabel biomolecules under mild conditions for PET imaging, a bifunctional (18)F prosthetic molecule has been developed. The compound, dubbed [(18)F]FPyPEGCBT, consists of a 2-substituted pyridine moiety for [(18)F]F(-) incorporation and a 2-cyanobenzothiazole moiety for coupling to terminal cysteine residues. The two functionalities are separated by a mini-PEG chain. [(18)F]FPyPEGCBT could be prepared from its corresponding 2-trimethylammonium triflate precursor (100 °C, 15 min, MeCN) in preparative yields of 11% ± 2 (decay corrected, n = 3) after HPLC purification. However, because the primary radiochemical impurity of the fluorination reaction will not interact with 1,2-aminothiol functionalities, the (18)F prosthetic could be prepared for bioconjugation reactions by way of partial purification on a molecularly imprinted polymer solid-phase extraction cartridge. [(18)F]FPyPEGCBT was used to (18)F-label a cyclo-(RGDfK) analogue which was modified with a terminal cysteine residue (TCEP·HCl, DIPEA, 30 min, 43 °C, DMF). Final decay-corrected yields of (18)F peptide were 7% ± 1 (n = 9) from end-of-bombardment. This novel integrin-imaging agent is currently being studied in murine models of cancer. We argue that [(18)F]FPyPEGCBT holds significant promise owing to its straightforward preparation, 'click'-like ease of use, and hydrophilic character. Indeed, the water-tolerant radio-bioconjugation protocol reported herein requires only one HPLC step for (18)F peptide purification and can be carried out remotely using a single automated synthesis unit over 124-132 min.
authors: University Hospitals of Geneva, Cyclotron Unit, Geneva, Switzerland. Yann.Seimbille@unige.ch.
authors: James A H
authors: JA
authors: Inkster
authors: Didier J
authors: DJ
authors: Colin
authors: Yann
authors: Y
authors: Seimbille
mesh_terms: D052160:Benzothiazoles / Q000138:chemical synthesis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D005462:Fluorine Radioisotopes; D009570:Nitriles / Q000138:chemical synthesis / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D019275:Radiopharmaceuticals; D012015:Reference Standards; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: C578355:2-cyanobenzothiazole; D052160:Benzothiazoles; D005462:Fluorine Radioisotopes; D009570:Nitriles; D010455:Peptides; D011725:Pyridines; D019275:Radiopharmaceuticals; D013438:Sulfhydryl Compounds; C023666:pyridine