Synthesis of [11C]SCH 23390 for dopamine D1 receptor studies.

The optimal conditions for the synthesis of 11C-labelled SCH 23390 by radio-methylation of its desmethyl precursor, SCH 24518, with [11C]iodomethane are described. Isocratic reversed phase HPLC was used for the purification of [11C]SCH 23390. The specific activity range in 30 runs was 10-235 Ci/mmol and average radiochemical yield was 72% based on [11C]iodomethane. Mean synthesis time was 40-60 min from the end of bombardment. Preliminary animal studies indicate that [11C]SCH 23390 would be useful in visualizing D1 receptors in a living brain by positron tomography.