N-[11C]methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB):: synthesis, quality control and biodistribution

N-[C-11]methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine ([C-11]MBDB) 3 was prepared by methylation of the demethyl precursor BDB with [C-11]CHI. The radiosynthesis was optimized with regard to temperature, reaction time and amount of precursor, best results (i.e., 84% radiochemical yield, based on [C-11]CH3I activity) were obtained using 3 mg BDB at a reaction temperature of 130 degrees C in 8 minutes. With respect to a facilitated workup routine, productions were performed with 0.6 mg BDB at 110 degrees C for 10 minutes, yielding more than 50% of 3. The radiochemical purity of the final tracer solution was >98%, the specific activity was determined to be 300 GBq/mu mol (8000 Ci/mmol). Biodistribution studies in rats showed two major metabolic pathways as indicated by an increasing liver uptake (9.1% ID/organ at 5 minutes to 21% ID/organ at 30 minutes) and a high urine activity (up to 16% ID/g). In brain tracer uptake was more than 1%, with a brain to blood ratio of almost 12 resulting from a very rapid blood clearance of 3.