The invention provides compounds having the formula (1): ##STR00001## wherein R1 is hydrogen, fluoro or methoxyl, R1 being in position 2, 3, 4 or 5 of the aromatic carbocycle; R2 is hydrogen or methyl; R3 is hydrogen, methyl or ethyl; and their pharmaceutically acceptable acid addition salts, hydrates of their pharmaceutically acceptable acid addition salts as well as the isomers and the tautomers thereof.