Synthesis of N‐[¹¹C]‐methyl‐L‐DOPA

The radiochemical synthesis of N‐[¹¹C‐methyl]‐L‐DOPA was accomplished by N‐methylation of the methyl and ethyl esters of L‐N‐tert‐butyl‐oxycarbonyl‐[β‐(3,4‐dimethoxyphenyl)] alaninate with [¹¹C]iodomethane using sodium hydride in tetrahydrofuran and deprotection of the N‐methyl intermediate with hydriodic acid. A catalytic influence of Kryptofix on the methylation reaction was observed. Using the ethyl ester precursor, the average specific activity at the end‐of‐synthesis was 972 mCi/μmole. The synthesis was completed in an average of 45 minutes following the end‐of‐bombardment.