Compounds of the formula I in which R 1, R 2 each, independently of one another, denote H, A, (CH 2) n Het or (CH 2)nAr, R 1 and R 2, together with the N atom to which they are bonded, also denote a saturated, unsaturated or aromatic mono- or bicyclic heterocycle, which may contain a further 1 to 3 N, O and/or S atoms and which is unsubstituted or mono-, di- or trisubstituted by Hal, A, (CH 2) n Het, (CH 2) n Ar, (CH 2) n OH, (CH 2) n OA, (CH 2) n NH 2, (CH 2) n COOH, (CH 2) n COOA, NHCOA, NA'COA, CONH 2, CONHA, CONAA', OC(=O)(CH 2) p NH 2 and/or =O (carbonyl oxygen), R 3 and R 4, together with the C atom to which they are bonded, also denote a saturated or unsaturated monocyclic C3-C10-carbocycle, which may contain a further 1 to 3 N, O and/or S atoms and which is unsubstituted or mono-, di- or trisubstituted by Hal, A, (CH 2) n OH, (CH 2) n OA, (CH 2) n NH 2, (CH 2) n COOH, (CH 2) n COOA, NHCOA, NA'COA, CONH 2, CONHA, CONAA', OC(=O)(CH 2) p NH 2 and/or =O (carbonyl oxygen), X denotes NR 5 R 6, CONR 5 R 6, CH 2 NR 5 R 6, COOR 5, -OR 5, CH 2 OR 5, COHet, Het, CONH(CH 2) p CN or CONH(CH 2) p NR 5 R 6, R 5, R 6 each, independently of one another, denote H, A, (CH 2) n Het or (CH 2) n Ar, Ar denotes phenyl, naphthyl, tetrahydronaphthyl or biphenyl, each of which is unsubstituted or mono-, di-, tri-, tetra- or pentasubstituted by A, Hal, (CH 2) n OA, (CH 2) n OH, (CH 2) n CN, SA, SOA, SO 2 A, NO 2, C≡CH, (CH 2) n COOH, CHO, (CH 2) n COOA, CONH 2, CONHA, CONAA', NHCOA, CH A, (CH 2) n NH 2, (CH 2) n NHA, (CH 2) n NAA', (CH 2) n NHSO 2 A, SO 2 NH(CH 2) n NH 2, SO 2 NH 2, SO 2 NHA, SO 2 NAA', CONH(CH 2) n COOA, CONH(CH 2) n COOH, NHCO(CH 2) n COOA, NHCO(CH 2) n COOH, CONH(CH 2) n NH 2, CONH(CH 2) n NHA, CONH(CH 2) n NAA', CONH(CH 2) n CN and/or (CH 2) n CH(NH 2)COOH, Het denotes a mono- or bicyclic saturated, unsaturated or aromatic heterocycle having 1 to 4 N, O and/or S atoms, which may be unsubstituted or mono-, di- or trisubstituted by A, OA, OH, phenyl, SH, S m A, Hal, NO 2, CN, COA, COOA, COObenzyl, CONH 2, CONHA, CONAA', SO 2 NH 2, NH 2, NHA, NAA', NHCOA, NHSO 2 A and/or =O (carbonyl oxygen), A, A' each, independently of one another, denote unbranched or branched alkyl having 1-10 C atoms, in which 1-3 non-adjacent CH 2 groups may be replaced by O, S, SO, SO 2, NH, NMe or NEt, and/or, in addition, 1-5 H atoms may be replaced by F and/or Cl, or cyclic alkyl having 3-8 C atoms, Hal denotes F, Cl, Br or I, n denotes 0, 1, 2, 3 or 4, p denotes 1, 2, 3 or 4, and pharmaceutically usable salts and stereoisomers thereof, including mixtures thereof in all ratios. R 1, R 2 each, independently of one another, denote H, A, (CH 2) n Het or (CH 2)nAr, R 1 and R 2, together with the N atom to which they are bonded, also denote a saturated, unsaturated or aromatic mono- or bicyclic heterocycle, which may contain a further 1 to 3 N, O and/or S atoms and which is unsubstituted or mono-, di- or trisubstituted by Hal, A, (CH 2) n Het, (CH 2) n Ar, (CH 2) n OH, (CH 2) n OA, (CH 2) n NH 2, (CH 2) n COOH, (CH 2) n COOA, NHCOA, NA'COA, CONH 2, CONHA, CONAA', OC(=O)(CH 2) p NH 2 and/or =O (carbonyl oxygen), R 3 and R 4, together with the C atom to which they are bonded, also denote a saturated or unsaturated monocyclic C3-C10-carbocycle, which may contain a further 1 to 3 N, O and/or S atoms and which is unsubstituted or mono-, di- or trisubstituted by Hal, A, (CH 2) n OH, (CH 2) n OA, (CH 2) n NH 2, (CH 2) n COOH, (CH 2) n COOA, NHCOA, NA'COA, CONH 2, CONHA, CONAA', OC(=O)(CH 2) p NH 2 and/or =O (carbonyl oxygen), X denotes NR 5 R 6, CONR 5 R 6, CH 2 NR 5 R 6, COOR 5, -OR 5, CH 2 OR 5, COHet, Het, CONH(CH 2) p CN or CONH(CH 2) p NR 5 R 6, R 5, R 6 each, independently of one another, denote H, A, (CH 2) n Het or (CH 2) n Ar, Ar denotes phenyl, naphthyl, tetrahydronaphthyl or biphenyl, each of which is unsubstituted or mono-, di-, tri-, tetra- or pentasubstituted by A, Hal, (CH 2) n OA, (CH 2) n OH, (CH 2) n CN, SA, SOA, SO 2 A, NO 2, C≡CH, (CH 2) n COOH, CHO, (CH 2) n COOA, CONH 2, CONHA, CONAA', NHCOA, CH A, (CH 2) n NH 2, (CH 2) n NHA, (CH 2) n NAA', (CH 2) n NHSO 2 A, SO 2 NH(CH 2) n NH 2, SO 2 NH 2, SO 2 NHA, SO 2 NAA', CONH(CH 2) n COOA, CONH(CH 2) n COOH, NHCO(CH 2) n COOA, NHCO(CH 2) n COOH, CONH(CH 2) n NH 2, CONH(CH 2) n NHA, CONH(CH 2) n NAA', CONH(CH 2) n CN and/or (CH 2) n CH(NH 2)COOH, Het denotes a mono- or bicyclic saturated, unsaturated or aromatic heterocycle having 1 to 4 N, O and/or S atoms, which may be unsubstituted or mono-, di- or trisubstituted by A, OA, OH, phenyl, SH, S m A, Hal, NO 2, CN, COA, COOA, COObenzyl, CONH 2, CONHA, CONAA', SO 2 NH 2, NH 2, NHA, NAA', NHCOA, NHSO 2 A and/or =O (carbonyl oxygen), A, A' each, independently of one another, denote unbranched or branched alkyl having 1-10 C atoms, in which 1-3 non-adjacent CH 2 groups may be replaced by O, S, SO, SO 2, NH, NMe or NEt, and/or, in addition, 1-5 H atoms may be replaced by F and/or Cl, or cyclic alkyl having 3-8 C atoms, Hal denotes F, Cl, Br or I, n denotes 0, 1, 2, 3 or 4, p denotes 1, 2, 3 or 4,