Synthesis, structural reassignment, and biological activity of type B MAO inhibitors based on the 5H-indeno[1,2-c]pyridazin-5-one core

The synthesis and enzyme inhibitor properties of reversible type B monoamine oxidase inhibitors are described. These compounds belong to the 5H-indeno[ 1,2-c] pyridazine family and possess a hydrophobic benzyloxy or 4,4,4-trifluorobutoxy side chain which, in contrast to a previous assignment, has been unambiguously located at C( 8) of the heterocyclic moiety. Investigation of the regioisomeric structures establishes that substitution of the 5H-indeno[ 1,2-c] pyridazin-5-one core at C( 7) vs C( 8) dramatically influences the MAO-inhibiting properties of these compounds.