Synthesis of 3,3-bis(3-fluorophenyl)-[2,3-<SUP>3</SUP>H<INF>2</INF>]-1-propanamine hydrochloride ([<SUP>3</SUP>H<INF>2</INF>]-NPS 846·HCl): a novel ligand for the NMDA receptor

3,3-Bis(3-fluorophenyl)-1-propanamine hydrochloride (NPS 846·HCl, 1a) is representative of a new class of diphenylpropylamine NMDA receptor antagonists. The corresponding radiolabelled ligand was prepared by catalytic tritiation of its precursor olefin (4), which was synthesized in a three-step reaction sequence starting from 3,3'-difluorobenzophenone (2). Catalytic tritiation of 4 was performed in a two-component solvent system ([3:1] 1,4-dioxane/methanol). The percentage of isotope incorporation was found to be dependent on the nature of the reaction solvent. Experiments with deuterium gas indicate that higher radiochemical incorporation can be obtained by reduction in either neat 1,4-dioxane or methyl alcohol-d. © 1998 John Wiley & Sons, Ltd.