[11C]-labeling of some caffeine derivatives for mapping adenosine A2a receptors by PET technique

[C-11]-labeled form of ten A(2a) adenosine receptor specific 8-styryl-7-methyl-xanthine derivatives ([C-11]-caffeines) were synthesised by N-methylation of the corresponding 8-styryl-xanthine derivatives using [C-11]-methyl iodide in optimized reaction conditions. The results show that the [C-11]-methylations take place with excellent radiochemical yields (35-93%), and can be utilised easily in online preparations. These labeled ligands may facilitate the positron emission tomographic (PET) investigation of adenosine A(2a) receptors.