Isoxazole derivatives

An isoxazole represented by the formula ##STR7## or salts thereof wherein Ar represents a phenyl group which may optionally be substituted with a halogen atom or a lower alkoxy group, or a pyridyl group, R.sup.1 represents a hydrogen atom, a lower alkyl or a group represented by a group Ar, R.sup.2 represents a hydrogen atom, or alternatively R.sup.1 and R.sup.2 are bound together and form a carbon-carbon bond, and Am represents an amino residue selected from the group consisting of the following residues:

• ##STR8## wherein R.sup.3 represents a hydrogen atom or a lower alkyl group, X.sup.1 and X.sup.2 each represent a hydrogen atom, a halogen atom or a trifluoromethyl group and Y represents O or S.