Abstract: A novel optically pure (−)-1-(Benzofuran-2-yl)-2-propylaminopentane as represented by the following formula, which contains no (+)-isomer, and the pharmaceutically acceptable acid salt thereof. These compounds have excellent CAE effect (catecholaminergic activity enhancer effect) which is the enhancing action of neurotransmitter catecholamine release, and are useful as psychotropic composition, antidepressants, composition for treating Parkinson's disease and/or Alzheimer's disease.

Abstract: Ethylamine derivatives of the formula (I): (wherein R1 is hydrogen, hydroxyl, lower alkoxy or halogen; R2 is alkyl having 2 to 5 carbon atoms; R3 is hydrogen, alkyl having 2 to 5 carbon atoms, alkylcarbonyl having 2 to 5 carbon atoms, aryl having 6 to 10 carbon atoms or arylalkyl having 7 to 11 carbon atoms; the ring is a bicyclic compound which consists of at least one benzene ring and may comprise a saturated or unsaturated five- or six-membered ring which may or may not have heteroatoms, providing that when the ring is indole or 1,3-benzodioxole, R2 and R3 do not constitute, at the same time, two carbon atoms members, and when R3 is hydrogen, the ring is a bicyclic compound which is not indole, benzothiophene or benzodioxole and R2 is alkyl having 3 to 5 carbon atoms and pharmaceutically acceptable acid addition salts thereof. These compounds are promising as psychotropic drugs, antidepressants, drugs for Parkinson's disease and/or drugs for Alzeimer's disease.