Abstract Monoamine oxidase B metabolizes 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP; 1) first to 1-methyl-4-phenyl-2, 3-dihydropyridinium salt (MPDP+; 5), and then to 1- methyl-4-phenylphridinium salt (MPP+; 7). Chemical synthesis of MPDP+ and its 5-methyl ...