Synthesis of a PET tau tracer [11C]PBB3 for imaging of Alzheimer's disease

The authentic standard PBB3 and its precursor N-desmethyl-PBB3 as well as TBS-protected N-desmethyl-PBB3 precursor for radiolabeling were synthesized from 5-bromo-2-nitropyridine, acrolein diethyl acetal, 6-methoxy-2-methylbenzothiazole, and diethylchlorophosphate with overall chemical yield 1% in six steps, 2% in five steps, and 1% in six steps, respectively. [C-11]PBB3 was prepared from either desmethyl-PBB3 or TBS-protected desmethyl-PBB3 with [C-11]CH3OTf through N-[C-11] methylation and isolated by HPLC combined with SPE in 20-25% and 15-20% radiochemical yield, respectively, based on [C-11]CO2 and decay corrected to end of bombardment (EOB). The radiochemical purity was > 99%, and the specific activity at EOB was 370-1110 GBq/mu mol with a total synthesis time of similar to 40-min from EOB. (C) 2015 Elsevier Ltd. All rights reserved.