The present invention relates to compounds according to the general formula wherein the dotted lines denote a single bond which is optionally present, with 2 dotted lines denoting a double bond; and wherein the symbols in particular have the following meanings: R1 and R2 are independently from each other selected from the group consisting of: H; OH; (=O); halogens; pseudohalogens; NH2; S(O)mR5; SO2NH2; C(O)R8; C(O)OR9; CONH2; C1-C2-alkyl substituted by NH2, OH, S(O)mR5, SO2NH2, C(O)R8, C(O)OR9, CONH2; C1-C2-alkoxy substituted by NH2, OH, S(O)mR5, SO2NH2, C(O)R8, C(O)OR9, CONH2; Ar denotes an unsubstituted mononuclear aryl group having 6 or 7 members, which aryl group is annulated to the neighbouring 5-membered cycle, and which may carry 1, 2 or 3 heteroatoms from the group N, O and S in its cycle; Y, Z denote independently from each other a nitrogen atom or a methylene group; X is a nitrogen atom or a methylene group; A is selected from the group consisting of: H; halogens and pseudohalogens; OH; =N(OH); NR12R13; OSO3-; S(O)mR14; SO2NR15R16; C(O)R17; C(O)OR18; CONR19R20; C(S)R21, C(S)OR22; unsubstituted and at least monosubstituted C1-C6-alkyl which can carry in its chain one or more non-adjacent heteroatoms from the group nitrogen and oxygen, and which, if substituted, carry at least one substituent which is preferably selected from the group consisting of: halogens, pseudohalogens, OH, NR12R13, OSO3-, S(O)mR14, SO2NR15R16, C(O)R17, C(O)OR18, CONR19R20, C(S)R21, C(S)OR22, and substituted and non-substituted aryl and substituted and non-substituted heteroaryl which, if substituted, carry at least one substituent from the group consisting of C1-C3-alkyl, C1-C3-alkoxy, halogens, pseudohalogens, and CF3. These compounds lend themselves for the manufacture of drugs. They are useful in the inhibition of DNA methylation, the inhibition of DNA methyltransferases, and may therefore be useful for the manufacture of pharmaceuticals for the treatment of developmental disorders such as Prader-Willi-Syndrome, Angelman-Syndrome (Happy Puppet Syndrome), Beckwith-Wiedemann-Syndrome, and proliferative diseases, such as coronary restenosis and neoplastic diseases, particularly colon carcinoma, familiary adenomatous polyposis carcinoma and hereditary non-polyposis colorectal cancer, prostate carcinoma, melanoma, non-Hodgkin lymphoma, acute lymphatic leukemia (ALL), chronic lymphatic leukemia (CLL), acute myeolid leukemia (AML), chronic myeloid leukemia (CML), or hepatocellular carcinoma. These compounds may also be used for other applications including the induction of cellular differentiation, diagnosis, and the use in screening assays.