1-Benzylcyclopropylamine and 1-(phenylcyclopropyl)methylamine: an inactivator and a substrate of monoamine oxidase.

1-Benzylcyclopropylamine (1) and 1-(phenylcyclopropyl)methylamine (2), cyclopropane analogues of phenethylamine, were tested as inactivators for monoamine oxidase (MAO). Compound 1 is a potent competitive reversible inhibitor of the oxidation of benzylamine and also is a mechanism-based inactivator. It requires 2.3 equiv of 1 to inactivate 1 equiv of MAO. The excess equivalents of 1 are converted into benzyl vinyl ketone. A one-electron mechanism of inactivation is proposed. Compound 2 is a substrate for MAO and is converted into 1-phenylcyclopropanecarboxaldehyde without inactivation of the enzyme. Mechanistic consequences are discussed as a result of this observation.