Preparation of some NCA [1-11C]acid chlorides as labelling agents

The [11C]carbonation of simple Grignard reagents (RMgX, R = Et, Pr, cyclo-Bu; X= Br) with cyclotron-produced [11C]carbon dioxide followed by direct treatment of the 11C adducts with phthaloyl dichloride and 2,6-di-t-butylpyridine affords [1-11C]acid chlorides in useful radiochemical yields (> 10-30%, decay-corrected from 11CO2), as assessed by HPLC and TLC of the labelled amides formed by reaction with 1,2,3,4-tetrahydroisoquinoline. With suitable precautions these [1-11C]acid chlorides can be isolated at high specific activity within 15 min from radionuclide production as labelling agents for potential radiopharmaceuticals for PET. The preparation of [1-11C]benzoyl chloride without isolation has also been demonstrated. (author)