Objectives: Arsenic-77 is a beta emitting radionuclide with nuclear properties suitable for radiotherapy (β max = 0.683 MeV, γ = 0.239 MeV (1.65%), half-life = 38.8 h). A fast chromatography method is under development to acquire high specific activity no-carrier-added 77As. The separated 77As radiolabeling chemistry is being evaluated to synthesize no-carrier-added [77As]dithiolarylarsines. Methods: No-carrier-added 77As was produced by neutron irradiation of an enriched 76GeO2 target. The target was dissolved in NaOH and H2O2 and neutralized with HCl. The 77As was separated as arsenate (77AsO43-) from the Ge using silica gel chromatography with ethanol-HCl eluents. The arsenate was reduced to 77As(III) with a monothiol, followed by a modified Bart reaction to afford [77As]p-ethoxyphenylarsonic acid, which was further reduced and complexed with dithiol ligands to generate [77As]dithiolarylarsines. The various parameters (reactant concentrations, temperature, time) were optimized to achieve higher yields. Radio-TLC and macroscopic standards were used to evaluate yields. Results: At the macroscopic level, various dithiolarylarsines have been synthesized and characterized. Using the macroscopic standards and chromatography, various reaction conditions (e. g., solvent, aryl donor, dithiol ligand, temperature, time) were evaluated to optimize the radiolabeling yield at the no carrier added (NCA) level of 77As. Conclusions: NCA synthesis of dithiolarylarsines was accomplished with the highest yield to date observed for [77As] p-ethoxyphenyl-1,2-ethanedithiolatoarsine at 95%. Further optimization studies are underway. Acknowledgments: Department of Energy (DOE) DE-SC0010283/SC0003851 grant; Department of Chemistry; the MURR; the NMR facility; the X-Ray facility, University of Missouri. References: [1] Jurisson, S. S., et al. Chemical Reviews 93.3 (1993): 1137-1156. [2] Cutler, Cathy S., et al. Chem. Rev 113.2 (2013): 858-883. [3] Hamilton, C. S. and Morgan J. F. Organic Reactions (1944)

77As complexes for potential PET and radiotherapy

251st National Meeting (2016)

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