RPRD | Comparison of various solvents for the radio-synthesis yield of [11C]P…

Yong-Hyun Cho, Jae Min Jeong*, Yun-Sang Lee, Hak Jeong Lee, Hong-Jae Lee, Hyun-Ju Kim, Dong Soo Lee

Pet center, Department of Nuclear Medicine, Seoul National University Hospital, Seoul, Korea

Purpose

[11C]PIB ([N-methyl-11C]2-(4'-methylaminophenyl)-6-hydroxybenzothiazole) is widely used for -amyloid plaque imaging. Radio-synthesis yields of [11C]PIB were reported to be less than 20% (end of synthesis, EOS) from recent reports. To improve the 11C- radiolabeling yield, we compared the yield of [11C]PIB synthesis using 5 different solvents; dimethylformamide (DMF), methylethylketone (MEK), diethylketone (DEK), t-butanol (t-BuOH) and cyclohexanone (c-HXO).

Materials and Methods

The [11C]CH3OTf was synthesized by the reported method and then captured in a HPLC loop, which contained 1 mg of desmethyl-PIB in each solvent, DMF, MEK, DEK, t- BuOH and c-HXO. After 1 min, the reaction mixture was purified with HPLC. The 11C- labeling yield in each solvent was calculated from the decay corrected radioactivity of [11C]CH3OH and final purified product.

Results

The decay corrected yield of [11C]PIB were 5% with DMF, 6.7% with MEK, 0.6% with DEK, 4.7% with t-BuOH and 38 % with c-HXO, respectively. When we used c-HXO as a solvent, we obtained [11C]PIB with mean radioactivity of 1.66  0.78 GBq and the specific activity of 42.5541.89 GBq/mol;(n=106).

Conclusion

We found c-HXO was the most adequate solvent for synthesis of [11C]PIB.