Radiosynthesis of ¹¹C-PK11195 by Using ¹¹CMethyl Triflate

The purpose of this study was to establish a new synthetic method of ¹¹C-PK11195. The automated radiosynthesis of ¹¹C-PK11195 was accomplished by ¹¹C-N-methylation of the corresponding desmethyl precursors (nor-PK11195) with ¹¹C-methyl triflate (¹¹C-CH₃-Triflate) by the domestic-made synthesizer. The effects on labeling yield by N-methylation were evaluated. The results showed that the labeling yield of ¹¹C-PK11195 was 51.7%±5.6％ under optimized synthesis conditions which were 0.5-1.0 mg nor-PK11195, 90 ℃ and 5 min. The radiochemical purity and chemical purity were higher than 98％, and the specific activity was above 0.21 TBq/g based on the HPLC UV analysis. ¹¹C-PK11195 with a higher labeling yield can be prepared from the methylated reaction of ¹¹C-CH₃-Triflate with nor-PK11195. The results indicated that the ¹¹C-N-methylation of nor-PK11195 with ¹¹C-CH₃-Triflate was an ideal synthetic method which required less nor-PK11195.