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UBC Theses and Dissertations

Studies on radiotracer precursor components : stabilities of phenylboronic acids and erroneous sources of fluoride Lozada, Jerome


The use of aryltrifluoroborate radiotracers previously developed in the Perrin lab at the University of British Columbia has been prolific in showcasing boron as an ¹⁸F-fluoride capturing agent. Their in-vivo use for PET-Imaging has been widely discussed and supported with radioimages, publications, and applications in PET including advantages for higher specific activity than other tracers currently in use. However the final synthesis of these ArBF₃-radiotracers include synthetic challenges, peptide-arylboronic acids were observed to deboronate giving rise to low radiochemical yields along with low effective specific activity for the final tracer. The interest and study in determining conditions, where deboronation of arylboronic acids may occur, and where increased ¹⁸F production or conversely limitations on ¹⁹F contaminants, would potentially increase the value of aryltrifluoroborates use in PET-imaging with fundamental improvements in transition from lab bench to clinical settings. The stabilities of ayrlboronic acids under alkaline conditions have not been previously explored in literature. Previous reports indicate that electron rich arylboronic acids decomposing under acidic media but does not address alkalinity. Chapter 2 details the kinetic data concerning a set of electronically withdrawing arylboronates that are evaluated in basic aqueous-organic conditions. It was discovered that only subsets of electron deficient diortho substituted arylboronates undergo deboronation under base-typical solutions. These findings were then related to insights towards reactions concerning C-C bond formation through the stabilities and their uses as aryltrifluoroborates in cancer imaging. Apart from the use of ArBF₃s as radioprosthetics, specific activity is of primary concern. Cyclotrons around the world use ¹⁸O-H₂O, for the nuclear production of ¹⁸F. It has widely been acknowledged that ¹⁹F pervades within the system. Chapter 3 identifies some of the potential sources of ¹⁹F-fluoride in order to enhance radiofluoridation yields of ¹⁸F-fluoride with the aryltrifluoroborates. This fundamental analysis has led to the discovery of increased ¹⁹F-fluoride following irradiation, as well as possible leaching from the tubing and channels used for primary transfer. This work re-opens the discussion of the basics of the scientific research where acceptable standards of low specific activity may yet be in question and improved upon.

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