Synthesis and biological evaluation of a lipophilic, fluorine-18-labeled 5-ethynyl-2′-deoxyuridine derivative
The synthesis and preliminary biological evaluation of a lipophilic, fluorine-18-labeled 5-ethynyl-2′-deoxyuridine derivative [ 18F]-3 is described. Initially, 5-ethynyl-2′-deoxyuridine 5 was synthesized by coupling trimethylsilyl protected acetylene to 5-iodo-2′-deoxyuridine 4, followed by deprotection in alkaline conditions. Compound 5 was then reacted with 4-(4′-iodophenyl)phenol to give 5-[4(4′-hydroxyphenyl)phenyl]ethynyl-2′-deoxyuridine 6. Compound 6 was reacted with BrCH2CH219/18F as alkylating agent to give stable or radiolabeled 3. The crude products were purified using reversed phase-high performance liquid chromatography to obtain compound 3 and [18F]-3 in 33 and 7.4% yield (decay corrected), respectively. The synthesis time to obtain pure [18F]-3 was about 60min (starting from BrCH2CH218F). The specific radioactivity of the tracer was between 74 and 222 GBq/μmol. The log P7.4 of [ 18F]-3 was found to be 2.4. However, biodistribution study in normal mice showed low uptake of the tracer in the brain. The affinity of compounds 6 and 3 for varicella-zoster virus thymidine kinase enzyme (VZV-TK) was examined in vitro and the results revealed that the fluorinated analog 3 has a poor affinity for the enzyme in contrast to the phenol precursor 6. Copyright © 2007 John Wiley & Sons, Ltd.
Chitneni, SK; De Ruymaeker, T; Balzarini, J; Verbruggen, AM; Bormans, GM
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