CA2345838C — Method for the synthesis of radiolabeled compounds

USPTO Abstract

A new method of [11C]-methylation is described which attains the goals of simplicity, high radiochemical yields, speed, versatility, and automation. A standard HPLC injection loop on a standard HPLC injection valve is loaded with a solution of precursor in DMF or DMSO (+ base if required). At ambient temperature [11C]-iodomethane is passed through the loop for 3-4 min with >90% trapping of activity. After a further 1-5 min, the contents of the loop are quantitatively injected onto the HPLC column for purification. Radiochemical yields are equal to or superior to conventional solution methods in all cases, even though no heat is applied. [11C]-Labelled radiotracers which have been prepared by this method for human or animal studies include Raclopride, Nmethylspiperone, Ro 15-1788, FLB 457, RTI-32, Rolipram, SCH 23390, and SKF 82957. Since no vials, transfer lines, cooling, heating, or sealing valves are required, no transfer losses occur, yields are high, and clean-up is minimal, this "loop method" is ideal for most radiopharmaceuticals prepared from [11C]-iodomethane.