Radiosynthesis of carbon-11 labeled 6-methyldopamine ([11C]MeDA)

A rapid and efficient n.c.a. radiosynthesis of 6-[11C]methyldopamine ([11C]MeDA) using the Stille cross-coupling reaction as a key step was developed. The labeling conditions for the formation of the intermediate compound (protected [11C]MeDA, [11C]7) were determined with respect to reaction temperature and time. The radiochemical yield 89±1.4% (decay-corrected) of the protected intermediate [11C]7 was obtained at a reaction temperature of 60 °C and a reaction time of 5 min using Pd2(dba)3/P(o-tolyl)3 and CsF/CuBr as a co-catalyst system. The overall yield after deprotection with 45% HBr at 140 °C for 10 min was 64±3.9% (decay-corrected) within a total preparation time of 40 min, including hydrolysis, HPLC purification and formulation.

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► Rapid and efficient radiomethylation of DA via Stille reaction was developed.
► Protected [11C]Me-DA was obtained with 89±1.4% RCY at 60 °C for 5 min.
► Overall yield of [11C]Me-DA after acidic deprotection was 64±3.9%.
► Total preparation time was 40 min, including HPLC purification and formulation.