The application describes new compounds of the formula
wherein
R1 is hydrogen, C1-C7 alkyl, or C4-C8 cycloalkylmethyl;
R2 is a single or multiple substitution of hydrogen, hydroxyl, C1-C7 alkoxy, or C1-C7 alkyl; and
R3 is a single or multiple substitution of hydrogen, hydroxyl, halogen, C1-C7 alkoxy, phenoxy, C1-C7 alkyl, or trifluoromethyl;
all stereoisomeric forms and mixtures thereof, and pharmaceutically acceptable addition salts thereof.