Synthesis of two dopamine D4 receptor ligands: C-11 labelled chromeno[3,4-c]pyridin-5-ones

The synthesis of two C-11 labelled chromeno[3,4-c]pyridin-5-ones for the vi sualisation of the dopamine D4 receptor subtype has been developed. The pro duction entailed an O-methylation of the O-desmethyl precursor with [C-11]i odomethane in the presence of tetrabutylammonium hydroxide. Subsequent puri fication by RPHPLC and formulation by tracer enrichment on a C18 Sep Pak pr ovided a solution which was suitable for human iv injection. Specific activ ity of the tracer averaged 37 GBq/mu mol at EOS and the radiochemical yield s were 65% (decay-corrected, based [C-11]CH3I). Total activity obtained was 5.6 - 7.4 GBq preparations have been demonstrated to be chemically radioch emically pure by HPLC.