Background
The radiochemists’ synthetic possibilities are limited, due to a lack of variation in building blocks for PET tracer synthesis. N-formamides are important building blocks for the synthesis of a large variety of biological active compounds1. As such they are also interesting for PET tracer synthesis upon labelling with carbon-11.
Aims
The aim was to develop a fast and easy synthesis method for 11C-labelled N-formamides and apply this in the synthesis of the long-acting β2 agonist: N-[formyl-11C]formoterol2.
Methods
11C-labelled N-formamides were prepared in one-pot starting by reduction of cyclotron produced [11C]CO2 to [11C]formic acid3, followed by N-11C-formylation of an amine. The N-11C-formylation reaction was achieved using the coupling agent BOP in pyridine. The synthesis route was developed using benzylamine as model substrate and was extended to other amines.
Results and Conclusion
N-[formyl-11C]benzylformamide could be isolated in 40±9% radiochemical yield, with 87±10% radiochemical purity and a molar activity higher than 100GBq/µmol in less than 26 min from EOB (n=3). A small series of 11C-labelled N-formamides was obtained with similar yields. This method will now be applied in the synthesis of N-[formyl-11C]formoterol.