There is disclosed a compound shown by a formula of ##STR1## wherein R.sub.1 is a hydrogen atom alkyl group having 1-4 carbon atoms or acyl group having 1-4 carbon atoms: R.sub.2 and R.sub.3 are a hydrogen atom, alkyl group having 1-4 carbon atoms, phenyl radical, halogen atom, cyano radical, acyl group having 1-4 carbon atoms, nitro radical, alkoxy group having 1 or 2 carbon atoms, or substituted or non-substituted amino group, respectively; n is an integer of 1-3; and dotted line means a possible ring, and a salt thereof. The compound and salt bind with muscarinic receptor in brain to develop a powerful actuation thereof and thus those can be used as an effective ingredient for preventing and curing senile dementias, and more particularly Alzheimer's disease.