A pharmaceutically acceptable salt of a compound of formula wherein Z is in which R is a hydrogen, a straight-chained or branched alkyl group or a cyclic organyl group, or an aralkyl or heteroaralkyl group; n is 1; X 1 is NH or N(lower alkyl) group and X 2 is methylene, or X 1 is methylene and X 2 is a bond; Y 1 is methylene and Y 2 is methylene, vinylene, ethylene, or a bond; Ar 1 and Ar 2 independently are unsubstituted or substituted phenyl groups, wherein at least one of Ar 1 and Ar 2 is p-substituted with a substituent selected from halogen, lower alkoxy, lower alkyl, and trifluoromethyl; and W is oxygen; and wherein the pharmaceutically acceptable salt is selected from the group consisting of acetate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, calcium, carbonate, chloride, clavulanate, citrate, dihydrochloride, fumarate, gluconate, glutamate, hydrobromide, hydrochloride, hydroxynaphthoate, iodide, isothionate, lactate, lactobionate, laurate, maleate, mandelate, mesylate, methylbromide, methylnitrate, methylsulfate, nitrate, N-methylglucamine ammonium salt, oleate, oxalate, phosphate/diphosphate, salicylate, stearate, sulfate, succinate, tannate, tartrate, tosylate, triethiodide and valerate salt; wherein: "cyclic organyl group" means an aliphatic, alicyclic group in which carbon atoms form a ring; "lower alkyl (group)" means a C 1-6 cyclic, straight-chained or branched aliphatic group connected via a carbon atom; "lower alkoxy (group)" means a C 1-6 cyclic or acyclic organyl group connected via an oxygen atom; "aralkyl group" means an aryl group connected via a lower alkylene group, wherein the aryl group of the aralkyl group may be substituted or unsubstituted; "heteroaralkyl group" means a heteroaryl group connected via a lower alkylene group, wherein the heteroaryl group of heteroaralkyl group may be substituted or unsubstituted; "aryl group" means an aromatic, preferably benzenoid or naphthoid, group connected via one of the ring-forming carbon atoms, and optionally carrying one or more substituents selected from halo, hydroxy, amino, cyano, nitro, alkylamido, acyl, lower alkoxy, lower alkyl, lower hydroxyalkyl, lower aminoalkyl, lower alkylamino, alkylsulfenyl, alkylsulfinyl, alkylsulfonyl, sulfamoyl, or trifluoromethyl; and "heteroaryl group" means an aromatic C 2-6 cyclic group containing one O or S atom or up to four N atoms, or a combination of one O or S atom with up to two N atoms, and their substituted as well as benzo- and pyrido-fused derivatives, preferably connected via one of the ring-forming carbon atoms, wherein the heteroaryl group may carry one or more substituents selected from halo, hydroxy, amino, cyano, nitro, alkylamido, acyl, lower alkoxy, lower alkyl, lower hydroxyalkyl, lower aminoalkyl, lower alkylamino, alkylsulfenyl, alkylsulfinyl, alkylsulfonyl, sulfamoyl, or trifluoromethyl. Z is in which R is a hydrogen, a straight-chained or branched alkyl group or a cyclic organyl group, or an aralkyl or heteroaralkyl group; n is 1; X 1 is NH or N(lower alkyl) group and X 2 is methylene, or X 1 is methylene and X 2 is a bond; Y 1 is methylene and Y 2 is methylene, vinylene, ethylene, or a bond; Ar 1 and Ar 2 independently are unsubstituted or substituted phenyl groups, wherein at least one of Ar 1 and Ar 2 is p-substituted with a substituent selected from halogen, lower alkoxy, lower alkyl, and trifluoromethyl; and W is oxygen; and "cyclic organyl group" means an aliphatic, alicyclic group in which carbon atoms form a ring; "lower alkyl (group)" means a C 1-6 cyclic, straight-chained or branched aliphatic group connected via a carbon atom; "lower alkoxy (group)" means a C 1-6 cyclic or acyclic organyl group connected via an oxygen atom; "aralkyl group" means an aryl group connected via a lower alkylene group, wherein the aryl group of the aralkyl group may be substituted or unsubstituted; "heteroaralkyl group" means a heteroaryl group connected via a lower alkylene group, wherein the heteroaryl group of heteroaralkyl group may be substituted or unsubstituted; "aryl group" means an aromatic, preferably benzenoid or naphthoid, group connected via one of the ring-forming carbon atoms, and optionally carrying one or more substituents selected from halo, hydroxy, amino, cyano, nitro, alkylamido, acyl, lower alkoxy, lower alkyl, lower hydroxyalkyl, lower aminoalkyl, lower alkylamino, alkylsulfenyl, alkylsulfinyl, alkylsulfonyl, sulfamoyl, or trifluoromethyl; and "heteroaryl group" means an aromatic C 2-6 cyclic group containing one O or S atom or up to four N atoms, or a combination of one O or S atom with up to two N atoms, and their substituted as well as benzo- and pyrido-fused derivatives, preferably connected via one of the ring-forming carbon atoms, wherein the heteroaryl group may carry one or more substituents selected from halo, hydroxy, amino, cyano, nitro, alkylamido, acyl, lower alkoxy, lower alkyl, lower hydroxyalkyl, lower aminoalkyl, lower alkylamino, alkylsulfenyl, alkylsulfinyl, alkylsulfonyl, sulfamoyl, or trifluoromethyl.