COMPARISON OF 2 SYNTHETIC METHODS TO OBTAIN [F-18] N-(2-AMINOETHYL)-5-FLUOROPYRIDINE-2-CARBOXAMIDE, A POTENTIAL MAO-B IMAGING TRACER FOR PET

The compound Ro 19-6327, N-(2-aminoethyl)-5-chloropyridine-2-carboxamide is known to inhibit reversibly and site specifically the enzyme monoamine oxidase B (MAO-B). The I-123-labelled iodo-analogue N-(2-aminoethyl)-5-iodopyridine-2-carboxamide (Ro 43-0463) was investigated successfully in human volunteers by means of SPET (Single Photon Emission Tomography). We developed therefore the synthesis and radiolabelling of the corresponding fluoro-analogue N-(2-aminoethyl)-5-fluoropyridine-2-carboxamide with F-18 in order to carry out PET (Positron Emission Tomography) investigations of MAO-B related neuropsychiatric diseases. For this purpose two synthetic approaches leading to the electrophilic and the nucleophilic methods of F-18 radiolabelling were undertaken. The nucleophilic approach appeared to be superior when factors such as precursor synthesis, beam time, specific activity and radiochemical purity of the product are considered.