Six amino acid derivatives of 1-(4-aminophenyl)-2-aminopropanes and their parent amines were synthezised and tested for their potency and selectivity in inhibiting monoamine oxidase (MAO) in vitro and in vivo. The amino acid derivatives were 300–1000 times less potent than the parent amines in inhibiting the MAO-A activity in a rat brain mitochondrial preparation in vitro. All compounds, except the (R)-valinamide derivative (22), were potent ...