A compound of the formula ##STR10## wherein R.sub.1 is hydrogen, alkyl, alkoxycarbonyl, phenyl or phenyl substituted with at least one substituent selected from halogen, alkyl, alkoxy, alkylthio, nitro and amino,
- R.sub.2 is (a) alkoxy, Co) cycloalkyloxy, (c) cycloalkyloxy substituted with at least one alkyl, (d) cycloalkylalkyloxy, (e) phenylalkyloxy, (f) polyfluoroalkyloxy, (g) cinnamyloxy or (h) --NR.sub.5 R.sub.6,
- R.sub.3 is (a) phenylamino, (b) phenylamino wherein the phenyl is substituted with at least one substituent selected from halogen, alkyl, alkoxy, alkylthio, carboxyl, hydroxyl, mono- or polyhydroxyalkyl, nitro, amino, acyl, cyano, sulphamoyl, carbamoyl, benzoyl, trifluoromethylsulphonamido, alkoxycarbonyl, phenylhydroxymethyl, piperidino, hydroxyiminoalkyl, alkoxyiminoalkyl, alkylsulphinyl, hydroxyaminocarbonyl, alkoxyaminocarbonyl, 5-tetrazolyl, 5-tetrazolylalkyl, sulpho, --alk-O-CO-alk, ---alk-O-alk, --alk-COOX, --O-alk-COOX, --alk'-COOX, --CH.dbd.CH-COOX, --CO-COOX, --alk-SO.sub.3 H, --CH.dbd.CH-alk', --C(.dbd.NOH)-COOX and --S-alk-COOX, (c) phenyl, (d) phenyl substituted with at least one substituent selected from halogen, alkyl, alkoxy and alkylthio, (e) naphthyl, (f) indolyl or (g) quinolyl,
- R.sub.4 is phenyl substituted with at least one substituent selected from halogen atoms, alkyl, alkoxy, hydroxyl, polyfluoroalkyl, nitro, alkylthio, alkoxycarbonyl, carboxyl, acylamino, methylenedioxy, polyfluoroalkoxy, trifluoromethylthio, phenoxy, phenyl, benzyl, phenylamino and --CO-NR.sub.5 R.sub.6,
- R.sub.5 and R.sub.6, which may be identical or different, are (a) hydrogen, (b) alkyl, (c) phenyl, (d) phenyl substituted with at least one substituent selected from halogen, alkyl, alkoxy and alkylthio, (e) indanyl, (f) cycloalkylalkyl, (g) cycloalkyl or (h) phenylalkyl, or alternatively R.sub.5 and R.sub.6, together with the nitrogen atom to which they are attached, form (a) a saturated or unsaturated mono- or polycyclic heterocycle containing 4 to 9 carbon atoms and at least one hetero atom selected from O, N, S, (b) a saturated or unsaturated mono- or polycyclic heterocycle containing 4 to 9 carbon atoms and at least one heteroatom selected from O, N, S substituted with at least one alkyl, alkoxy, alkoxycarbonyl, dialkylcarbamoyl, phenyl, 4- or 5-membered spiromonocyclic ring formed with a carbon atom of the heterocycle or 4- or 5-membered spiromonocyclic ring formed with a carbon atom of the heterocycle and containing at least one hetero atom selected from O, S, N,
- alk is alkyl or alkylene,
- alk' is hydroxyalkylene or hydroxyalkyl,
- X is hydrogen or alkyl, wherein the alkyl, alkylene and alkoxy radicals and alkyl, alkylene and alkoxy portions contain 1 to 4 carbon atoms in the straight or branched chain, and wherein the cycloalkyl radicals and portions contain 3 to 6 carbon atoms, wherein the acyl radicals contain 2 to 4 carbon atoms, as well as its racemates and its enantiomers when it contains at least one asymmetric centers.