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  Immunosuppresive effects of pteridine derivativesUSPTO Application #: 20070043000Title: Immunosuppresive effects of pteridine derivatives Abstract: Novel poly-substituted pteridinediones (lumazines), and mono- or polysubstituted 2-thiolumazines, 4-thiolumazines or 2,4-dithiolumazines, having disclosed substituents in positions 1, 3, 6 and 7 of the pteridine ring, and pharmaceutically acceptable salts thereof, are useful as biologically active ingredients in preparing pharmaceutical compositions especially for the treatment or prevention of a CNS disorder, a cell proliferative disorder, a viral infection, an immune or auto-immune disorder or a transplant rejection. Combinations of the pteridine derivatives of the invention with an immunosuppressant or immunomodulator drug, an antineoplastic drug or an antiviral agent, providing potential synergistic effects, are also disclosed. (end of abstract) Agent: Clark & Elbing LLP - Boston, MA, US Inventors: Mark Jozef Albert Waer, Piet Andre Maurits Maria Herdewijn, Wolfgang Eugen Pfleiderer USPTO Applicaton #: 20070043000 - Class: 514081000 (USPTO) Related Patent Categories: Drug, Bio-affecting And Body Treating Compositions, Designated Organic Active Ingredient Containing (doai), Phosphorus Containing Other Than Solely As Part Of An Inorganic Ion In An Addition Salt Doai, Nitrogen Containing Hetero Ring, Polycylo Ring System Having A Ring Nitrogen In The System, Nonshared Hetero Atoms In At Least Two Rings Of The Polycyclo Ring System The Patent Description & Claims data below is from USPTO Patent Application 20070043000. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention relates to a class of novel poly-substituted pteridine-2,4-diones (lumazines), as well as novel mono- and polysubstituted 2-thiolumazines, 4-thiolumazines and 2,4-dithiolumazines. The invention further relates to pharmaceutical compositions including a broad class of poly-substituted pteridine-2,4-diones (lumazines), as well as mono- and polysubstituted 2-thiolumazines, 4-thiolumazines and 2,4-dithiolumazines especially for the prevention and/or the treatment of pathologic conditions such as, but not limited to, immune and autoimmune disorders, organ and cells transplant rejections, cell proliferative disorders, cardiovascular disorders, disorders of the central nervous system and viral diseases. [0002] The invention further relates to combined pharmaceutical preparations comprising one or more polysubstituted pteridine-2,4-diones (lumazines), as well as mono- and polysubstituted 2-thiolumazines, 4-thiolumazines and 2,4-dithiolumazines and one or more known immunosuppressant drugs or antineoplastic drugs or anti-viral drugs. [0003] This invention also relates to a method for the prevention and/or treatment of pathologic conditions such as, but not limited to, immune and autoimmune disorders, organ and cells transplant rejections, cell proliferative disorders, cardiovascular disorders, disorders of the central nervous system and viral diseases by the administration of an effective amount of a polysubstituted pteridine-2,4-dione (lumazine), or a mono- or polysubstituted 2-thiolumazine, 4-thiolumazine or 2,4-dithio-lumazine optionally combined with one or more known immunosuppressant drugs or antineoplastic drugs or anti-viral drugs. Finally the invention relates to a method for selecting or classifying biologically active polysubstituted pteridine-2,4-diones (lumazines), as well as mono- and polysubstituted 2-thiolumazines, 4-thiolumazines and 2,4dithiolumazines based on the determination of two or more in vitro tests such as TNF-.alpha. and IL-1 .beta. assays. BACKGROUND OF THE INVENTION [0004] 2,4-dioxo-1,2,3,4-tetrahydropteridine is well known in the art under the name lumazine. Gabriel and Sonn first disclosed in Ber. Deut. Chem. Ges. (1907) 40:4850 making lumazine from pyrazin-bicarboxamide. Timmis in Nature (1949) 164:139 disclosed the synthesis of 1,3-dimethyl-6-phenyllumazine and 1,3-dimethyl-7-phenyl-lumazine by condensing a 6-amino-5-nitroso-pyrimidine with benzaldehyde or methylphenylketone respectively. Zondler et al. in J. Heterocyclic Chem. (1967) 4:124 and Taylor et al. in Heterocycles (1978) 10:37 disclosed 1,3,6-trimethyllumazine and 1,3-dimethyl-6-ethyllumazine. Yoneda and Higuchi in J. Chem. Soc. Perkin (1977) 1336 disclosed the preparation of various 1,3-dimethyl-6-aryllumazines starting from 6-amino-1,3-dimethyl-5-aryliden-aminouracil. Kang et al. in J. Heterocycl. Chem. (1987) 24:597-601 disclosed reacting 5,6-diamino-1,3-dimethyluracil either with propanetrione-1,3-dioxime followed by cyclization to form 1,3-dimethyllumazine-6-carboxaldoxime, or with oximinoacetone followed by cyclization to form 1,3,6-trimethyllumazine, or else with methylglyoxal to form 1,3,7-trimethyllumazine. Both latter compounds may easily, through acid hydrolysis in the presence of formaldehyde, be converted into the corresponding 1,3-dimethyllumazine-carboxaldehydes which, due to their high carbonyl reactivity, may in turn be converted into other lumazine derivatives. Blicke et al. in J.A.C.S (1954) 76:2798-2800 disclosed 1,3-dimethyl-7-aminolumazine, 1,3,6,7-tetramethyllumazine, 1,3-dimethyl6,7-dihydroxy-lumazine and 1,3-dimethyl-6,7-diphenylumazine; Pfleiderer in Chem. Ber. (1957) 90:2588 disclosed 1,3-dimethyl-6-hydroxylumazine and 1,3-dimethyl-7-hydroxylumazine; Pfleiderer et al. in Chem. Ber. (1973) 106:3149-3174 disclosed 1,3-dimethyl6-hydroxy-7-phenyllumazine, 1,3-dimethyl-6-phenyl-7-hydroxy-lumazine and 1,3-dimethyl-6,7-diisopropylumazine; Hutzenlaub et al. in Chem. Ber. (1973) 106:3203-3215 disclosed 1,3-dimethyl-7-methoxylumazine, 1,3,6-trimethyl-7-hydroxy-lumazine and 1,3,6-trimethyl-7-methoxylumazine; Steppan et al. in Liebigs Ann. Chem. (1982) 2135-2145 disclosed 1,3dimethyl-6-aminolumazine, 1,3-dimethyl-6-chlorolumazine, 1,3-dimethyl-7-chlorolumazine and 1,3-dimethyl-7-methylaminolumazine; Kasimierczuk et al. in Chem. Ber. (1979) 112:1499-1513 disclosed 1,3-dimethyl-7-mercaptolumazine and 1,3-dimethyl-7-methylthio-lumazine as well as a few substituted 2- or 4-thiolumazines and 2,4-dithiolumazines, starting from substituted 6-amino-2-thiouracil or 6-amino-2,4-dithiouracil; Eisele et al. in Pteridines (1993) 4:178-186 disclosed 1,3,6-trimethyllumazine-7-carboxylic acid and its methyl and ethyl esters. Perez-Rubalcaba et al. in Liebigs Ann. Chem. (1983) 852-859 disclosed substituted 3-methyllumazines wherein one of the 6- and 7-substituents is phenyl whereas the other is chloro. Finally, Weisenfeldt (1987) disclosed a series of tetra-substituted lumazines wherein the 1- and 3-substituents are methyl and one of the 6- and 7-substituents is chloro. Further, Fink et al. in Chem. Berichte (1963) 96:2950-2963, as well as Pfleiderer, Perez-Rubalcaba and Eisele (all cited supra) disclosed bi- and tri-substituted lumazines wherein only one of the 1- and 3-nitrogen atoms is substituted. Interestingly, none of the above-cited substituted lumazines, 2-thiolumazines and 2,4-dithiolumazines was ever said to have any kind of biological activity. [0005] A few other substituted pteridine-2,4-diones (lumazines) are already known in the art as being useful in the preparation of medicines. For instance, U.S. Pat. No. 3,071,587 teaches cyanoethylpteridinediones having central nervous system (hereinafter referred as CNS) activity and anti-depressant properties. WO 94/06431 teaches a 1-methyl-3-(10,11-epoxyundecyl)pteridine-dione being able to inhibit IL-1 receptors, decrease proliferation of tumor & other cells, stimulate hematopoeisis, suppress T-cell activation, secretion of antibodies by B-cells and activation of macrophage or endothelial cells by endotoxins, tumor necrosis factor (hereinafter TNF), IL-1 or GM-CSF and enhance resistance of mesenchymal cells to TNF. WO 94/11001 teaches 1-methyl-3-(hydroxy- and dihydroxy-C.sub.9-25 alkyl) pteridinediones being able to inhibit lysophosphatidic acid transferase as well as immune or cellular response to stimuli, and therefore can be used to treat tumor progression or invasion, autoimmune diseases, acute allergic reactions mediated by TNF or IL-1, rheumatoid arthritis, osteoarthritis, multiple sclerosis, diabetes, atherosclerosis, restenosis, stroke, HIV infection, inflammatory response, septic shock, CNS and bone diseases. Cottam et al. in J. Med. Chem. (1996) 39:2-9 and WO 98/52948 both disclose a 1-methyl-3-n-hexyl-6-carboxymethyl-7-carboxymethyl pteridine-dione which, although included in a biological evaluation study of inhibitors of TNF-.alpha., was not tested for TNF-.alpha. activity. WO 96/20710 teaches substituted pteridinediones which inhibit cellular responses to ceramide metabolites of the sphingomyelin signal transduction pathway, inhibit inflammatory response associated with TNF-.alpha. and fibroblast proliferation or UV-induced cutaneous immune suppression and therefore can be used to treat cirrhosis, cell senescence and apoptosis. [0006] WO 00/45800 discloses the immunosuppressive effects of pharmaceutical compositions for the treatment of autoimmuno disorders and/or for the treatment or prevention of transplant rejections comprising a pteridine derivative of general formula: wherein: [0007] R.sub.1 and R.sub.2 are independently hydrogen; aliphatic saturated or unsaturated, straight or branched carbon chains with 1 to 7 carbon atoms; substituted or unsubstituted aryl or alkylaryl substituents, whereby the carbon atoms may be oxidized represented by alcohol or carbonyl function or carboxylic acids and their esters; [0008] R.sub.3 and R.sub.4 are independently hydrogen, hydroxyl, halogen, alkyl, haloalkyl, alkoxy, wherein the alkyl group may be branched or straight and contains one or four carbon atoms, formyl and derivatives such as hydroxylamino conjugates and acetals, cyano, carboxylic acids and carboxyl acid derivatives such as esters and amides, sulfhydryl, amino, alkylamino, cycloalkylamino, alkenylamino, alkynyl-amino, benzylamino, hydroxylalkylamino, morpholinoalkylamino, phenylhydra-zino, morpholino, piperidino, mercaptobenzyl, mercaptoalkyl, cysteinyl ester, styryl, aromatic ring; aromatic or heterocyclic substituent substituted with an aliphatic spacer between the pteridine ring and the aromatic substituent of 1 to 4 carbon atoms, whereby said spacer may contain an alcohol function, carbonyl function, halogen, ether, and may be saturated or unsaturated; branched or straight, saturated or unsaturated aliphatic chain of 1 to 7 carbon atoms which may contain one or more functions chosen from the group comprising carbonyl, alcohol, ether, carboxyester nitro, thioalkyl, halogen; and [0009] Y.sub.1 and Y.sub.2 are both oxygen, or a pharmaceutical salt thereof, and a pharmaceutically acceptable carrier. [0010] WO 00/45800 also discloses a compound, 1,3-dimethyl-6-benzoyl-7-(4-methoxyphenyl)lumazine, which has poor results in a Mixed Lymphocyte Reaction test as well as in CD3 and CD 28 assays. [0011] WO 03/067257 discloses making 3-methyl6-iminouracil in a three-steps procedure starting from O-methylisourea hydrochloride and methylcyanoacetate with a combined yield of 29%, followed by conversion into 5,6-diamino-3-methyluracil. C. Muller et al. in J. Med. Chem. (2002) 45:3440-3450 discloses 5,6-diamino-1-benzyluracil and a procedure for making it. [0012] Nevertheless, there still is a need in the art for specific and highly therapeutically active compounds, such as, but not limited to, drugs for treating immune and autoimmune disorders, organ and cells transplant rejections, cell proliferative disorders, cardiovascular disorders, disorders of the central nervous system and viral diseases. In particular, there is a need in the art to provide immunosuppressive compounds or antineoplastic drugs or anti-viral drugs which are active in a minor dose in order to replace existing drugs having significant side effects and to decrease treatment costs. [0013] Currently used immunosuppressive drugs include antiproliferative agents, such as methotrexate, azathioprine, and cyclophosphamide. Since these drugs affect mitosis and cell division, they have severe toxic effects on normal cells with high turn-over rate such as bone marrow cells and the gastrointestinal tract lining. Accordingly, marrow depression and liver damage are common side effects. [0014] Anti-inflammatory compounds used to induce immunosuppression include adrenocortical steroids such as dexamethasone and prednisolone. The common side effects observed with the use of these compounds are frequent infections, abnormal metabolism, hypertension, and diabetes. [0015] Other immunosuppressive compounds currently used to inhibit lymphocyte activation and subsequent proliferation include cyclosporine, tacrolimus and rapamycin. Cyclosporine and its relatives are among the most commonly used immunosuppressant drugs. Cyclosporine is typically used for preventing or treating organ rejection in kidney, liver, heart, pancreas, bone marrow, and heart-lung transplants, as well as for the treatment of autoimmune and inflammatory diseases such as Crohn's disease, aplastic anemia, multiple sclerosis, myasthenia gravis, uveitis, biliary cirrhosis, etc. However, cyclosporines suffer from a small therapeutic dose window and severe toxic effects including nephrotoxicity, hepatotoxicity, hypertension, hirsutism, cancer, and neurotoxicity. Another such drug, mitoxantrone, is known to induce heart and kidney toxicity. [0016] Additionally, monoclonal antibodies with immunosuppressant properties, such as OKT3, have been used to prevent and/or treat graft rejection. Introduction of such monoclonal antibodies into a patient, as with many biological materials, induces several side-effects, such as dyspnea. Within the context of many life-threatening diseases, organ transplantation is considered a standard treatment and, in many cases, the only alternative to death. The immune response to foreign cell surface antigens on the graft, encoded by the major histo-compatibility complex (hereinafter referred as MHC) and present on all cells, generally precludes successful transplantation of tissues and organs unless the transplant tissues come from a compatible donor and the normal immune response is suppressed. Other than identical twins, the best compatibility and thus, long term rates of engraftment, are achieved using MHC identical sibling donors or MHC identical unrelated cadaver donors. However, such ideal matches are difficult to achieve. Further, with the increasing need of donor organs an increasing shortage of transplanted organs currently exists. Accordingly, xenotransplantation has emerged as an area of intensive study, but faces many hurdles with regard to rejection within the recipient organism. [0017] The host response to an organ allograft involves a complex series of cellular interactions among T and B lymphocytes as well as macrophages or dendritic cells that recognize and are activated by foreign antigen. Co-stimulatory factors, primarily cytokines, and specific cell-cell interactions, provided by activated accessory cells such as macrophages or dendritic cells are essential for T-cell proliferation. These macrophages and dendritic cells either directly adhere to T-cells through specific adhesion proteins or secrete cytokines that stimulate T-cells, such as IL-12 and IL-15. Accessory cell-derived co-stimulatory signals stimulate activation of interleukin-2 (IL-2) gene transcription and expression of high affinity IL-2 receptors in T-cells. IL-2 is secreted by T lymphocytes upon antigen stimulation and is required for normal immune responsiveness. IL-2 stimulates lymphoid cells to proliferate and differentiate by binding to IL-2 specific cell surface receptors (IL-2R). IL-2 also initiates helper T-cell activation of cytotoxic T-cells and stimulates secretion of interferon-.gamma. which in turn activates cytodestructive properties of macrophages. Furthermore, IFN-.gamma. and IL-4 are also important activators of MHC class II expression in the transplanted organ, thereby further expanding the rejection cascade by enhancing the immunogenicity of the grafted organ The current model of a T-cell mediated response suggests that T-cells are primed in the T-cell zone of secondary lymphoid organs, primarily by dendritic cells. The initial interaction requires cell to cell contact between antigen-loaded MHC molecules on antigen-presenting cells (hereinafter referred as APC) and the T-cell receptor/CD3 complex on T-cells. Engagement of the TCR/CD3 complex induces CD154 expression predominantly on CD4 T-cells that in turn activate the APC through CD40 engagement, leading to improved antigen presentation. This is caused partly by upregulation of CD80 and CD86 expression on the APC, both of which are ligands for the important CD28 co-stimulatory molecule on T-cells. However, engagement of CD40 also leads to prolonged surface expression of MHC-antigen complexes, expression of ligands for 4-1BB and OX40 (potent co-stimulatory molecules expressed on activated T-cells). Furthermore, CD40 engagement leads to secretion of various cytokines (e.g., IL-12, IL-15, TNF-.alpha., IL-1, IL-6, and IL-8) and chemokines, all of which have important effects on both APC and T-cell activation and maturation. Similar mechanisms are involved in the development of auto-immune disease, such as type I diabetes. In humans and non-obese diabetic mice, insulin-dependent diabetes mellitus results from a spontaneous T-cell dependent auto-immune destruction of insulin-producing pancreatic .beta. cells that intensifies with age. The process is preceded by infiltration of the islets with mononuclear cells (insulitis), primarily composed of T lymphocytes. A delicate balance between auto-aggressive T-cells and suppressor-type immune phenomena determine whether expression of auto-immunity is limited to insulitis or not. Therapeutic strategies that target T-cells have been successful in preventing further progress of the auto-immune disease. These include neonatal thymectomy, administration of cyclosporine, and infusion of anti-pan T-cell, anti-CD4, or anti-CD25 (IL-2R) monoclonal antibodies. The aim of all rejection prevention and auto-immunity reversal strategies is to suppress the patient's immune reactivity to the antigenic tissue or agent, with a minimum of morbidity and mortality. Accordingly, a number of drugs are currently being used or investigated for their immunosuppressive properties. As discussed above, the most commonly used immunosuppressant is cyclosporine, which however has numerous side effects. Accordingly, in view of the relatively few choices for agents effective at immunosuppression with low toxicity profiles and manageable side effects, there exists a need in the art for identification of alternative immunosuppressive agents and for agents acting as complement to calcineurin inhibition. [0018] There is also a need in the art to improve therapeutic efficiency by providing pharmaceutical compositions or combined preparations exhibiting a synergistic effect as a result of combining two or more immunosuppressant drugs, or antineoplastic drugs or anti-viral drugs. SUMMARY OF THE INVENTION [0019] In a first embodiment, the present invention relates to a group of novel poly-substituted pteridine-2,4-diones (lumazines), as well as novel mono- and poly-substituted 2-thiolumazines, 4-thiolumazines and 2,4-dithiolumazines and their pharmaceutically acceptable salts and enantiomers. These compounds may be represented by the general formula (I): wherein: [0020] a) if Y.sub.1 and Y.sub.2 are both oxygen and R.sub.4 is hydrogen, then: [0021] R.sub.1 is a radical selected from the group consisting of hydrogen; C.sub.1-5 alkyl; C.sub.2-7 alkenyl; aryl; alkylaryl; .omega.-hydroxy C.sub.1-7 alkyl; .omega.-epoxy C.sub.1-7 alkyl; .omega.-carboxy C.sub.1-7 alkyl (wherein the carboxy group may be acid, ester, thioester, acid halide or amide); .omega.-cyano C.sub.1-7 alkyl; arylalkyl; arylalkenyl; heterocyclic-substituted alkyl; heterocyclic-substituted alkenyl; groups having the formula --S--R (i.e. wherein a sulfur atom is attached to the nitrogen atom of the pteridine ring) wherein R is a monovalent group selected from the group consisting of C.sub.1-7 alkyl, aryl and C.sub.3-10 cycloalkyl and wherein the said monovalent group is optionally substituted with one or more substituents selected from the group consisting of amino, amino-acid, alkylamino, arylamino, cycloalkylamino, carboxylic acid, carboxylic ester, sulfonic acid and phosphonic acid; and optionally substituted heterocyclic radicals preferably selected from the group consisting of diazepinyl, oxadiazinyl, thiadiazinyl, dithiazinyl, triazolonyl, diazepinonyl, triazepinyl, triazepinonyl, tetrazepinonyl, benzoquinolinyl, benzothiazinyl, benzothiazinonyl, benzoxathiinyl, benzodioxinyl, benzodithiinyl, benzoxazepinyl, benzothiazepinyl, benzodiazepinyl, benzodioxepinyl, benzodithiepinyl, benzoxazocinyl, benzothiazocinyl, benzodiazocinyl, benzoxathiocinyl, benzodioxocinyl, benzotrioxepinyl, benzoxathiazepinyl, benzoxadiazepinyl, benzothiadiazepinyl, benzotriazepinyl, benzoxathiepinyl, benzotriazinonyl, benzoxazolinonyl, azetidinonyl, azaspiroundecyl, dithiaspirodecyl, selenazinyl, selenazolyl, selenophenyl, hypoxanthinyl, azahypoxanthinyl, bipyrazinyl, bipyridinyl, oxazolidinyl, diselenopyrimidinyl, benzopyrenyl, benzopyranonyl, benzophenazinyl, benzoquinolizinyl, dibenzocarbazolyl, dibenzoacridinyl, dibenzophenazinyl, dibenzothiepinyl, dibenzooxepinyl, dibenzopyranonyl, dibenzoquinoxalinyl, dibenzothiazepinyl, dibenzoisoquinolinyl, tetraazaadamantyl, thiatetraazaadamantyl, oxauracil, oxazinyl, dibenzothiophenyl, dibenzofuranyl, oxazolinyl, oxazolonyl, azaindolyl, azolonyl, thiazolinyl, thiazolonyl, thiazolidinyl, thiazanyl, pyrimidonyl, thiopyrimidonyl, thiamorpholinyl, azlactonyl, naphtindazolyl, naphtindolyl, naphtothiazolyl, naphtothioxolyl, naphtoxindolyl, naphtotriazolyl, naphtopyranyl, indolinyl, indolizidinyl, oxabicycloheptyl, azabenzimidazolyl, azacycloheptyl, azacyclooctyl, azacyclononyl, azabicyclononyl, tetrahydropyranyl, tetrahydropyronyl, tetrahydroquinoleinyl, tetrahydrothienyl and dioxide thereof, dihydrothienyl dioxide, dioxindolyl, dioxinyl, dioxenyl, dioxazinyl, thioxanyl, thioxolyl, thiourazolyl, thiotriazolyl, thiopyranyl, thiopyronyl, coumarinyl, quinoleinyl, oxyquinoleinyl, quinuclidinyl, xanthinyl, dihydropyranyl, benzodihydrofuryl, benzothiopyronyl, benzothiopyranyl, benzoxazinyl, benzoxazolyl, benzodioxolyl, benzodioxanyl, benzothiadiazolyl, benzotriazinyl, benzothiazolyl, benzoxazolyl, phenothioxinyl, phenothiazolyl, phenothienyl, phenopyronyl, phenoxazolyl, pyridinyl, dihydropyridinyl, tetrahydropyridinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, benzotriazolyl, tetrazolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, pyrrolyl, furyl, dihydrofuryl, furoyl, hydantoinyl, dioxolanyl, dioxolyl, dithianyl, dithienyl, dithiinyl, thienyl, indolyl, indazolyl, benzofuryl, benzothienyl, quinolyl, quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenothiazinyl, xanthenyl, purinyl, benzothienyl, naphtothienyl, thianthrenyl, pyranyl, pyronyl, benzo-pyronyl, isobenzofuranyl, chromenyl, phenoxathiinyl, indolizinyl, quinolizinyl, isoquinolyl, phthalazinyl, naphthiridinyl, cinnolinyl, pteridinyl, carbolinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, imidazo-linyl, imidazolidinyl, benzimidazolyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, piperazinyl, uridinyl, thymidinyl, cytidinyl, azirinyl, aziridinyl, diazirinyl, diaziridinyl, oxiranyl, oxaziridinyl, dioxiranyl, thiiranyl, azetyl, dihydroazetyl, azetidinyl, oxetyl, oxetanyl, thietyl, thietanyl, oxetanonyl, diaza-bicyclooctyl, diazetyl, diaziridinonyl, diaziridinethionyl, chromanyl, chroma-nonyl, thiochromanyl, thiochromanonyl, thiochromenyl, benzofuranyl, benzisothiazolyl, benzocarbazolyl, benzochromonyl, benzisoalloxazinyl, benzocoumarinyl, thiocoumarinyl, phenometoxazinyl, phenoparoxazinyl, phentriazinyl, thiodiazinyl, thiodiazolyl, indoxyl, thioindoxyl, benzodiazinyl (e.g. phtalazinyl), phtalidyl, phtalimidinyl, phtalazonyl, alloxazinyl, dibenzo-pyronyl (i.e. xanthonyl), xanthionyl, isatyl, isopyrazolyl, isopyrazolonyl, urazolyl, urazinyl, uretinyl, uretidinyl, succinyl, succinimido, benzylsultimyl, and benzylsultamyl; [0022] R.sub.2 is a radical selected from the group consisting of hydrogen; C.sub.1-5 alkyl; C.sub.2-7 alkenyl; aryl; alkylaryl; .omega.-hydroxy C.sub.1-7 alkyl; .omega.-epoxy C.sub.1-7 alkyl; .omega.-carboxy C.sub.1-7 alkyl (wherein the carboxy group may be acid, ester, thioester, acid halide or amide); .omega.-cyano C.sub.1-7 alkyl; arylalkyl; arylalkenyl; heterocyclic-substituted alkyl; heterocyclic-substituted alkenyl; groups having the formula --S--R (i.e. wherein a sulfur atom is attached to the nitrogen atom of the pteridine ring) wherein R is a monovalent group selected from the group consisting of C.sub.1-7 alkyl, aryl and C.sub.3-10 cycloalkyl and wherein the said monovalent group is optionally substituted with one or more substituents selected from the group consisting of amino, amino-acid, alkylamino, arylamino, cycloalkylamino, carboxylic acid, carboxylic ester, sulfonic acid and phosphonic acid; and optionally substituted heterocyclic radicals preferably other than tetrahydrofuryl, i.e. preferably selected from the group consisting of diazepinyl, oxadiazinyl, thiadiazinyl, dithiazinyl, triazolonyl, diazepinonyl, triazepinyl, triazepinonyl, tetrazepinonyl, benzoquinolinyl, benzothiazinyl, benzothiazinonyl, benzoxathiinyl, benzodioxinyl, benzodithiinyl, benzoxazepinyl, benzothiazepinyl, benzodiazepinyl, benzodioxepinyl, benzodithiepinyl, benzoxazocinyl, benzothiazocinyl, benzodiazocinyl, benzoxathiocinyl, benzodioxocinyl, benzotrioxepinyl, benzoxathiazepinyl, benzoxadiazepinyl, benzothiadiazepinyl, benzotriazepinyl, benzoxathiepinyl, benzotriazinonyl, benzoxazolinonyl, azetidinonyl, azaspiroundecyl, dithiaspirodecyl, selenazinyl, selenazolyl, selenophenyl, hypoxanthinyl, azahypoxanthinyl, bipyrazinyl, bipyridinyl, oxazolidinyl, diselenopyrimidinyl, benzodioxocinyl, benzopyrenyl, benzopyranonyl, benzophenazinyl, benzoquinolizinyl, dibenzocarbazolyl, dibenzoacridinyl, dibenzophenazinyl, dibenzothiepinyl, dibenzooxepinyl, dibenzopyranonyl, dibenzoquinoxalinyl, dibenzothiazepinyl, dibenzoisoquinolinyl, tetraazaadamantyl, thiatetraazaadamantyl, oxauracil, oxazinyl, dibenzothiophenyl, dibenzofuranyl, oxazolinyl, oxazolonyl, azaindolyl, azolonyl, thiazolinyl, thiazolonyl, thiazolidinyl, thiazanyl, pyrimidonyl, thiopyrimidonyl, thiamorpholinyl, aziactonyl, naphtindazolyl, naphtindolyl, naphtothiazolyl, naphtothioxolyl, naphtoxindolyl, naphtotriazolyl, naphtopyranyl, indolinyl, indolizidinyl, oxabicycloheptyl, azabenzimidazolyl, azacycloheptyl, azacyclooctyl, azacyclononyl, azabicyclononyl, tetrahydropyranyl, tetrahydropyronyl, tetrahydroquinoleinyl, tetrahydrothienyl and dioxide thereof, dihydrothienyl dioxide, dioxindolyl, dioxinyl, dioxenyl, dioxazinyl, thioxanyl, thioxolyl, thio-urazolyl, thiotriazolyl, thiopyranyl, thiopyronyl, coumarinyl, quinoleinyl, oxyquinoleinyl, quinuclidinyl, xanthinyl, dihydropyranyl, benzodihydrofuryl, benzothiopyronyl, benzothiopyranyl, benzoxazinyl, benzoxazolyl, benzodioxolyl, benzodioxanyl, benzothiadiazolyl, benzotriazinyl, benzothiazolyl, benzoxazolyl, phenothioxinyl, phenothiazolyl, phenothienyl, phenopyronyl, phenoxazolyl, pyridinyl, dihydropyridinyl, tetrahydropyridinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, benzotriazolyl, tetrazolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, pyrrolyl, furyl, dihydrofuryl, furoyl, hydantoinyl, dioxolanyl, dioxolyl, dithianyl, dithienyl, dithiinyl, thienyl, indolyl, indazolyl, benzofuryl, benzothienyl, quinolyl, quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenothiazinyl, xanthenyl, purinyl, benzothienyl, naphtothienyl, thianthrenyl, pyranyl, pyronyl, benzopyronyl, isobenzofuranyl, chromenyl, phenoxathiinyl, indolizinyl, quinolizinyl, isoquinolyl, phthalazinyl, naphthiridinyl, cinnolinyl, pteridinyl, carbolinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, imidazolinyl, imidazolidinyl, benzimidazolyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, piperazinyl, uridinyl, thymidinyl, cytidinyl, azirinyl, aziridinyl, diazirinyl, diaziridinyl, oxiranyl, oxaziridinyl, dioxiranyl, thiiranyl, azetyl, dihydroazetyl, azetidinyl, oxetyl, oxetanyl, thietyl, thietanyl, oxetanonyl, diaza-bicyclooctyl, diazetyl, diaziridinonyl, diaziridinethionyl, chromanyl, chroma-nonyl, thiochromanyl, thiochromanonyl, thiochromenyl, benzofuranyl, benzisothiazolyl, benzocarbazolyl, benzochromonyl, benzisoalloxazinyl, benzocoumarinyl, thiocoumarinyl, phenometoxazinyl, phenoparoxazinyl, phentriazinyl, thiodiazinyl, thiodiazolyl, indoxyl, thioindoxyl, benzodiazinyl (e.g. phtalazinyl), phtalidyl, phtalimidinyl, phtalazonyl, alloxazinyl, dibenzo-pyronyl (i.e. xanthonyl), xanthionyl, isatyl, isopyrazolyl, isopyrazolonyl, urazolyl, urazinyl, uretinyl, uretidinyl, succinyl, succinimido, benzylsultimyl, and benzylsultamyl; [0023] at most one of R.sub.1 and R.sub.2 is hydrogen; and [0024] R.sub.3 is an atom or radical selected from the group consisting of fluorine; iodine; C.sub.3-4 alkyl; C.sub.2-7 alkenyl; C.sub.2-7 alkynyl; C.sub.3-4 haloalkyl; C.sub.1-2 haloalkyl wherein halo is fluoro or chloro; C.sub.1-4 alkoxy; C.sub.3-10 cycloalkoxy; aryloxy; arylalkyloxy; oxyheterocyclic; heterocyclic-substituted alkyloxy; thio C.sub.1-7 alkyl; thio C.sub.3-10 cycloalkyl; thioaryl; thioheterocyclic; arylalkylthio; heterocyclic-substituted alkylthio; hydroxylamino; acetal; carboxylic acid esters, thioesters and amides; thiocarboxylic acid; thiocarboxylic acid esters, thioesters and amides; sulfhydryl; C.sub.2-7 alkylamino; cycloalkylamino; alkenylamino; cycloalkenylamino; alkynylamino; arylamino; arylalkylamino; hydroxyalkylamino; mercaptoalkyl-amino; heterocyclic amino; heterocyclic-substituted alkylamino; oximino; alkyloximino; hydrazino; alkylhydrazino; phenylhydrazino; cysteinyl acid, esters or amides; aryl substituted with one or more substituents selected from the group consisting of halogen, C.sub.1-4 alkyl, C.sub.3-7 alkenyl, C.sub.2-7 alkynyl, C.sub.1-4 haloalkyl, C.sub.2-4 alkoxy, hydroxyl, sulfhydryl, amino, C.sub.3-10 cycloalkoxy, aryloxy, arylalkyloxy, oxyheterocyclic, heterocyclic-substituted alkyloxy, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, thioaryl, thioheterocyclic, arylalkylthio, heterocyclic-substituted alkylthio, formyl, hydroxylamino, cyano, carboxylic acid or esters or thioesters or amides thereof, thiocarboxylic acid or esters or thioesters or amides thereof, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxylalkyl-amino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino and phenylhydrazino; optionally substituted heterocyclic radicals; aryl or heterocyclic radicals substituted with an aliphatic spacer (linking group) between the pteridine ring and the aryl or heterocyclic radical, whereby said aliphatic spacer is a branched or straight, saturated or unsaturated aliphatic chain of 2 to 4 carbon atoms which may contain one or more functions, atoms or radicals selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkyl-amino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen, or whereby said aliphatic spacer is a methylene group containing a function, atom or radical chosen from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkyl-amino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen; branched or straight, saturated or unsaturated aliphatic chain of 3 to 7 carbon atoms containing one or more functions selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid ester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxylalkylamino, mercaptoalkyl-amino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen; hydroxyethyl; oximinoethyl; alkyl-oximinoethyl; and methyl or ethyl or ethenyl containing one or more atoms, functions or radicals selected from the group consisting of ether, acetal, amino, imino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cyclo-alkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido, fluoro and chloro; [0025] b) if Y.sub.1 and Y.sub.2 are both oxygen and R.sub.3 is hydrogen, then: [0026] R.sub.1 is a radical selected from the group consisting of hydrogen; C.sub.1-5 alkyl; C.sub.2-7 alkenyl; aryl; alkylaryl; .omega.-hydroxy C.sub.1-5 alkyl; .omega.-epoxy C.sub.1-5 alkyl; .omega.-carboxy C.sub.1-5 alkyl (wherein the carboxy group may be acid, ester, thioester, acid halide or amide); .omega.-cyano C.sub.1-7 alkyl; arylalkyl; arylalkenyl; heterocyclic-substituted alkyl; heterocyclic-substituted alkenyl; groups having the formula --S--R (i.e. wherein a sulfur atom is attached to the nitrogen atom of the pteridine ring) wherein R is a monovalent group selected from the group consisting of C.sub.1-7 alkyl, aryl and C.sub.3-10 cycloalkyl and wherein the said monovalent group is optionally substituted with one or more substituents selected from the group consisting of amino, amino-acid, alkylamino, arylamino, cycloalkylamino, carboxylic acid, carboxylic ester, sulfonic acid and phosphonic acid; and optionally substituted heterocyclic radicals preferably selected from the group consisting of diazepinyl, oxadiazinyl, thiadiazinyl, dithiazinyl, triazolonyl, diazepinonyl, triazepinyl, triazepinonyl, tetrazepinonyl, benzoquinolinyl, benzothiazinyl, benzothiazinonyl, benzoxathiinyl, benzodioxinyl, benzodithiinyl, benzoxazepinyl, benzothiazepinyl, benzodiazepinyl, benzodioxepinyl, benzodithiepinyl, benzoxazocinyl, benzothiazocinyl, benzodiazocinyl, benzoxathiocinyl, benzodioxocinyl, benzotrioxepinyl, benzoxathiazepinyl, benzoxadiazepinyl, benzothiadiazepinyl, benzo-triazepinyl, benzoxathiepinyl, benzotriazinonyl, benzoxazolinonyl, azetidinonyl, azaspiroundecyl, dithiaspirodecyl, selenazinyl, selenazolyl, selenophenyl, hypoxanthinyl, azahypoxanthinyl, bipyrazinyl, bipyridinyl, oxazolidinyl, diselenopyrimidinyl, benzopyrenyl, benzopyranonyl, benzophenazinyl, benzoquinolizinyl, dibenzocarbazolyl, dibenzoacridinyl, dibenzophenazinyl, dibenzothiepinyl, dibenzooxepinyl, dibenzopyranonyl, dibenzoquinoxalinyl, dibenzothiazepinyl, dibenzoisoquinolinyl, tetraaza-adamantyl, thiatetraazaadamantyl, oxauracil, oxazinyl, dibenzothiophenyl, dibenzofuranyl, oxazolinyl, oxazolonyl, azaindolyl, azolonyl, thiazolinyl, thiazolonyl, thiazolidinyl, thiazanyl, pyrimidonyl, thiopyrimidonyl, thiamorpholinyl, azlactonyl, naphtindazolyl, naphtindolyl, naphtothiazolyl, naphtothioxolyl, naphtoxindolyl, naphtotriazolyl, naphtopyranyl, indolinyl, indolizidinyl, oxabicycloheptyl, azabenzimidazolyl, azacycloheptyl, azacyclooctyl, azacyclononyl, azabicyclononyl, tetrahydropyranyl, tetrahydropyronyl, tetrahydroquinoleinyl, tetrahydrothienyl and dioxide thereof, dihydrothienyl dioxide, dioxindolyl, dioxinyl, dioxenyl, dioxazinyl, thioxanyl, thioxolyl, thio-urazolyl, thiotriazolyl, thiopyranyl, thiopyronyl, coumarinyl, quinoleinyl, oxyquinoleinyl, quinuclidinyl, xanthinyl, dihydropyranyl, benzodihydrofuryl, benzothiopyronyl, benzothiopyranyl, benzoxazinyl, benzoxazolyl, benzodioxolyl, benzodioxanyl, benzothiadiazolyl, benzotriazinyl, benzothiazolyl, benzoxazolyl, phenothioxinyl, phenothiazolyl, phenothienyl, phenopyronyl, phenoxazolyl, pyridinyl, dihydropyridinyl, tetrahydropyridinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, benzotriazolyl, tetrazolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, pyrrolyl, furyl, dihydrofuryl, furoyl, hydantoinyl, dioxolanyl, dioxolyl, dithianyl, dithienyl, dithiinyl, thienyl, indolyl, indazolyl, benzofuryl, benzothienyl, quinolyl, quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenothiazinyl, xanthenyl, purinyl, benzothienyl, naphtothienyl, thianthrenyl, pyranyl, pyronyl, benzopyronyl, isobenzofuranyl, chromenyl, phenoxathiinyl, indolizinyl, quinolizinyl, isoquinolyl, phthalazinyl, naphthiridinyl, cinnolinyl, pteridinyl, carbolinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, imidazolinyl, imidazolidinyl, benzimidazolyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, piperazinyl, uridinyl, thymidinyl,cytidinyl, azirinyl, aziridinyl, diazirinyl, diaziridinyl, oxiranyl, oxaziridinyl, dioxiranyl, thiiranyl, azetyl, dihydroazetyl, azetidinyl, oxetyl, oxetanyl, thietyl, thietanyl, oxetanonyl, diaza-bicyclooctyl, diazetyl, diaziridinonyl, diaziridinethionyl, chromanyl, chroma-nonyl, thiochromanyl, thiochromanonyl, thiochromenyl, benzofuranyl, benzisothiazolyl, benzocarbazolyl, benzochromonyl, benzisoalloxazinyl, benzocoumarinyl, thiocoumarinyl, phenometoxazinyl, phenoparoxazinyl, phentriazinyl, thiodiazinyl, thiodiazolyl, indoxyl, thioindoxyl, benzodiazinyl (e.g. phtalazinyl), phtalidyl, phtalimidinyl, phtalazonyl, alloxazinyl, dibenzo-pyronyl (i.e. xanthonyl), xanthionyl, isatyl, isopyrazolyl, isopyrazolonyl, urazolyl, urazinyl, uretinyl, uretidinyl, succinyl, succinimido, benzylsultimyl, and benzylsultamyl; [0027] R.sub.2 is a radical selected from the group consisting of hydrogen; C.sub.1-5 alkyl; C.sub.2-7 alkenyl; aryl; alkylaryl; .omega.-hydroxy C.sub.1-7 alkyl; .omega.-epoxy C.sub.1-7 alkyl; .omega.-carboxy C.sub.1-7 alkyl (wherein the carboxy group may be acid, ester, thioester, acid halide or amide); .omega.-cyano C.sub.1-7 alkyl; arylalkyl; arylalkenyl; heterocyclic-substituted alkyl; heterocyclic-substituted alkenyl; groups having the formula --S--R (i.e. wherein a sulfur atom is attached to the nitrogen atom of the pteridine ring) wherein R is a monovalent group selected from the group consisting of C.sub.1-7 alkyl, aryl and C.sub.3-10 cycloalkyl and wherein the said monovalent group is optionally substituted with one or more substituents selected from the group consisting of amino, amino-acid, alkylamino, arylamino, cycloalkylamino, carboxylic acid, carboxylic ester, sulfonic acid and phosphonic acid; and optionally substituted heterocyclic radicals preferably selected from the group consisting of diazepinyl, oxadiazinyl, thiadiazinyl, dithiazinyl, triazolonyl, diazepinonyl, triazepinyl, triazepinonyl, tetrazepinonyl, benzoquinolinyl, benzothiazinyl, benzothiazinonyl, benzoxathiinyl, benzodioxinyl, benzodithiinyl, benzoxazepinyl, benzothiazepinyl, benzodiazepinyl, benzodioxepinyl, benzodithiepinyl, benzoxazocinyl, benzothiazocinyl, benzodiazocinyl, benzoxathiocinyl, benzodioxocinyl, benzotrioxepinyl, benzoxathiazepinyl, benzoxadiazepinyl, benzothiadiazepinyl, benzotri-azepinyl, benzoxathiepinyl, benzotriazinonyl, benzoxazolinonyl, azetidinonyl, azaspiroundecyl, dithiaspirodecyl, selenazinyl, selenazolyl, selenophenyl, hypoxanthinyl, azahypoxanthinyl, bipyrazinyl, bipyridinyl, oxazolidinyl, diselenopyrimidinyl, benzopyrenyl, benzopyranonyl, benzophenazinyl, benzoquinolizinyl, dibenzocarbazolyl, dibenzoacridinyl, dibenzophenazinyl, dibenzothiepinyl, dibenzooxepinyl, dibenzopyranonyl, dibenzoquinoxalinyl, dibenzothiazepinyl, dibenzoisoquinolinyl, tetraazaadamantyl, thiatetraazaadamantyl, oxauracil, oxazinyl, dibenzothiophenyl, dibenzofuranyl, oxazolinyl, oxazolonyl, azaindolyl, azolonyl, thiazolinyl, thiazolonyl, thiazolidinyl, thiazanyl, pyrimidonyl, thiopyrimidonyl, thiamorpholinyl, azlactonyl, naphtindazolyl, naphtindolyl, naphtothiazolyl, naphtothioxolyl, naphtoxindolyl, naphtotriazolyl, naphtopyranyl, indolinyl, indolizidinyl, oxabicycloheptyl, azabenzimidazolyl, azacycloheptyl, azacyclooctyl, azacyclononyl, azabicyclononyl, tetrahydropyranyl, tetrahydropyronyl, tetrahydroquinoleinyl, tetrahydrothienyl and dioxide thereof, dihydrothienyl dioxide, dioxindolyl, dioxinyl, dioxenyl, dioxazinyl, thioxanyl, thioxolyl, thio-urazolyl, thiotriazolyl, thiopyranyl, thiopyronyl, coumarinyl, quinoleinyl, oxyquinoleinyl, quinuclidinyl, xanthinyl, dihydropyranyl, benzodihydrofuryl, benzothiopyronyl, benzothiopyranyl, benzoxazinyl, benzoxazolyl, benzodioxolyl, benzodioxanyl, benzothiadiazolyl, benzotriazinyl, benzothiazolyl, benzoxazolyl, phenothioxinyl, phenothiazolyl, phenothienyl, phenopyronyl, phenoxazolyl, pyridinyl, dihydropyridinyl, tetrahydropyridinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, benzotriazolyl, tetrazolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, pyrrolyl, furyl, dihydrofuryl, furoyl, hydantoinyl, dioxolanyl, dioxolyl, dithianyl, dithienyl, dithiinyl, thienyl, indolyl, indazolyl, benzofuryl, benzothienyl, quinolyl, quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenothiazinyl, xanthenyl, purinyl, benzothienyl, naphtothienyl, thianthrenyl, pyranyl, pyronyl, benzopyronyl, isobenzofuranyl, chromenyl, phenoxathiinyl, indolizinyl, quinolizinyl, isoquinolyl, phthalazinyl, naphthiridinyl, cinnolinyl, pteridinyl, carbolinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, imidazolinyl, imidazolidinyl, benzimidazolyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, piperazinyl, uridinyl, thymidinyl,cytidinyl, azirinyl, aziridinyl, diazirinyl, diaziridinyl, oxiranyl, oxaziridinyl, dioxiranyl, thiiranyl, azetyl, dihydroazetyl, azetidinyl, oxetyl, oxetanyl, thietyl, thietanyl, oxetanonyl, diazabicyclooctyl, diazetyl, diaziridinonyl, diaziridinethionyl, chromanyl, chromanonyl, thiochromanyl, thiochromanonyl, thiochromenyl, benzofuranyl, benzisothiazolyl, benzocarbazolyl, benzochromonyl, benzisoalloxazinyl, benzocoumarinyl, thiocoumarinyl, phenometoxazinyl, phenoparoxazinyl, phentriazinyl, thiodiazinyl, thiodiazolyl, indoxyl, thioindoxyl, benzodiazinyl (e.g. phtalazinyl), phtalidyl, phtalimidinyl, phtalazonyl, alloxazinyl, dibenzo-pyronyl (i.e. xanthonyl), xanthionyl, isatyl, isopyrazolyl, isopyrazolonyl, urazolyl, urazinyl, uretinyl, uretidinyl, succinyl, succinimido, benzylsultimyl, and benzylsultamyl; [0028] at most one of R.sub.1 and R.sub.2 is hydrogen; and [0029] R.sub.4 is an atom or radical selected from the group consisting of fluoro; iodo; C.sub.3-4 alkyl; C.sub.2-7 alkenyl; C.sub.2-7 alkynyl; halo C.sub.3-4 alkyl; halo C.sub.1-2 alkyl wherein halo is fluoro or chloro; C.sub.1-4 alkoxy; C.sub.3-10 cycloalkoxy; aryloxy; arylalkyloxy; oxyheterocyclic; heterocyclic-substituted alkyloxy; thio C.sub.1-7 alkyl; thio C.sub.3-10 cycloalkyl; thioaryl; thioheterocyclic; arylalkylthio; heterocyclic-substituted alkylthio; hydroxylamino; acetal; carboxylic acid esters, thioesters and amides; thiocarboxylic acid; thiocarboxylic acid esters, thioesters and amides; sulfhydryl; C.sub.2-7 alkylamino; cycloalkylamino; alkenylamino; cycloalkenylamino; alkynylamino; arylamino; arylalkylamino; hydroxyalkylamino; mercaptoalkyl-amino; heterocyclic amino; heterocyclic-substituted alkylamino; oximino; alkyloximino; hydrazino; alkylhydrazino; phenylhydrazino; cysteinyl acid, esters or amides; aryl substituted with one or more substituents selected from the group consisting of halogen, nitro, C.sub.1-7 alkyl, C.sub.2-7 alkenyl, C.sub.2-7 alkynyl, halo C.sub.1-7 alkyl, methoxy, C.sub.2-7 alkoxy, hydroxyl, sulfhydryl, amino, C.sub.3-10 cycloalkoxy, aryloxy, arylalkyloxy, oxyheterocyclic, heterocyclic-substituted alkyloxy, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, thioaryl, thioheterocyclic, arylalkylthio, heterocyclic-substituted alkylthio, formyl, hydroxylamino, cyano, carboxylic acid or esters or thioesters or amides thereof, thiocarboxylic acid or esters or thioesters or amides thereof, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxylalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino and phenylhydrazino; optionally substituted heterocyclic radicals preferably other than morpholino and piperidino, i.e. preferably selected from the group consisting of diazepinyl, oxadiazinyl, thiadiazinyl, dithiazinyl, triazolonyl, diazepinonyl, triazepinyl, triazepinonyl, tetrazepinonyl, benzoquinolinyl, benzothiazinyl, benzothiazinonyl, benzoxathiinyl, benzodi-oxinyl, benzodithiinyl, benzoxazepinyl, benzothiazepinyl, benzodiazepinyl, benzodioxepinyl, benzodithiepinyl, benzoxazocinyl, benzothiazocinyl, benzodiazocinyl, benzoxathiocinyl, benzodioxocinyl, benzotrioxepinyl, benzoxathiazepinyl, benzoxadiazepinyl, benzothiadiazepinyl, benzotri-azepinyl, benzoxathiepinyl, benzotriazinonyl, benzoxazolinonyl, azetidinonyl, azaspiroundecyl, dithiaspirodecyl, selenazinyl, selenazolyl, selenophenyl, hypoxanthinyl, azahypoxanthinyl, bipyrazinyl, bipyridinyl, oxazolidinyl, diselenopyrimidinyl, benzopyrenyl, benzopyranonyl, benzophenazinyl, benzoquinolizinyl, dibenzocarbazolyl, dibenzoacridinyl, dibenzophenazinyl, dibenzothiepinyl, dibenzooxepinyl, dibenzopyranonyl, dibenzoquinoxalinyl, dibenzothiazepinyl, dibenzoisoquinolinyl, tetraazaadamantyl, thiatetraaza-adamantyl, oxauracil, oxazinyl, dibenzothiophenyl, dibenzofuranyl, oxazolinyl, oxazolonyl, azaindolyl, azolonyl, thiazolinyl, thiazolonyl, thiazolidinyl, thiazanyl, pyrimidonyl, thiopyrimidonyl, thiamorpholinyl, azlactonyl, naphtindazolyl, naphtindolyl, naphtothiazolyl, naphtothioxolyl, naphtoxindolyl, naphtotriazolyl, naphtopyranyl, indolinyl, indolizidinyl, oxabicycloheptyl, azabenzimidazolyl, azacycloheptyl, azacyclooctyl, azacyclononyl, azabicyclononyl, tetrahydrofuryl, tetrahydropyranyl, tetrahydropyronyl, tetrahydroquinoleinyl, tetrahydrothienyl and dioxide thereof, dihydrothienyl dioxide, dioxindolyl, dioxinyl, dioxenyl, dioxazinyl, thioxanyl, thioxolyl, thio-urazolyl, thiotriazolyl, thiopyranyl, thiopyronyl, coumarinyl, quinoleinyl, oxyquinoleinyl, quinuclidinyl, xanthinyl, dihydropyranyl, benzodihydrofuryl, benzothiopyronyl, benzothiopyranyl, benzoxazinyl, benzoxazolyl, benzo-dioxolyl, benzodioxanyl, benzothiadiazolyl, benzotriazinyl, benzothiazolyl, benzoxazolyl, phenothioxinyl, phenothiazolyl, phenothienyl, phenopyronyl, phenoxazolyl, pyridinyl, dihydropyridinyl, tetrahydropyridinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, benzotriazolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, pyrrolyl, furyl, dihydrofuryl, furoyl, dioxolyl, dithienyl, dithiinyl, thienyl, indolyl, indazolyl, benzofuryl, benzothienyl, quinolyl, quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenothiazinyl, xanthenyl, purinyl, benzothienyl, naphtothienyl, thianthrenyl, pyranyl, pyronyl, benzopyronyl, isobenzofuranyl, chromenyl, phenoxathiinyl, indolizinyl, quinolizinyl, isoquinolyl, phthalazinyl, naphthiridinyl, cinnolinyl, pteridinyl, carbolinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, imidazolinyl, benzimidazolyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, piperazinyl, uridinyl, thymidinyl, cytidinyl, azirinyl, aziridinyl, diazirinyl, diaziridinyl, oxiranyl, oxaziridinyl, dioxiranyl, thiiranyl, azetyl, dihydroazetyl, azetidinyl, oxetyl, oxetanyl, thietyl, thietanyl, oxetanonyl, diazabicyclooctyl, diazetyl, diaziridinonyl, diaziridinethionyl, chromanyl, chromanonyl, thiochromanyl, thiochromanonyl, thiochromenyl, benzofuranyl, benzisothiazolyl, benzocarbazolyl, benzochromonyl, benzisoalloxazinyl, benzocoumarinyl, thiocoumarinyl, phenometoxazinyl, phenoparoxazinyl, phentriazinyl, thiodiazinyl, thiodiazolyl, indoxyl, thioindoxyl, benzodiazinyl (e.g. phtalazinyl), phtalidyl, phtalimidinyl, phtalazonyl, alloxazinyl, dibenzopyronyl (i.e. xanthonyl), xanthionyl, isatyl, isopyrazolyl, isopyrazolonyl, urazolyl, urazinyl, uretinyl, uretidinyl, succinyl, succinimido, benzylsultimyl, and benzylsultamyl; aryl or heterocyclic radicals substituted with an aliphatic spacer between the pteridine ring and the aryl or heterocyclic radical, whereby said aliphatic spacer is a branched or straight, saturated or unsaturated aliphatic chain of 2 to 4 carbon atoms which may contain one or more functions, atoms or radicals selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C .sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen, or whereby said aliphatic spacer is a methylene group containing a function, atom or radical chosen from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido, fluoro and chloro; branched or straight, saturated or unsaturated aliphatic chain of 3 to 7 carbon atoms containing one or more functions selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, aminoacid, cyano, carboxylic acid ester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen; hydroxyethyl; oximinoethyl; alkyloximinoethyl; and methyl or ethyl or ethenyl containing one or more functions, atoms or radicals selected from the group consisting of ether, acetal, amino, imino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenyl-amino, alkynylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido, fluoro and chloro; [0030] c) if one or more of Y.sub.1 and Y.sub.2 is sulfur and at most one of Y.sub.1 and Y.sub.2 is oxygen, then: [0031] each of R.sub.1 and R.sub.2 is a radical independently selected from the group consisting of hydrogen; C.sub.1-7 alkyl; C.sub.2-7 alkenyl; aryl; alkylaryl; .omega.-hydroxy C.sub.1-7 alkyl; .omega.-epoxy C.sub.1-7 alkyl; .omega.-carboxy C.sub.1-7 alkyl (wherein the carboxy group may be acid, ester, thioester, acid halide or amide); .omega.-cyano C.sub.1-7 alkyl; arylalkyl; arylalkenyl; heterocyclic-substituted alkyl; heterocyclic-substituted alkenyl; groups having the formula --S--R (i.e. wherein a sulfur atom is attached to the nitrogen atom of the pteridine ring) wherein R is a monovalent group selected from the group consisting of C.sub.1-7 alkyl, aryl and C.sub.3-10 cycloalkyl and wherein the said monovalent group is optionally substituted with one or more substituents selected from the group consisting of amino, amino-acid, alkylamino, arylamino, cycloalkylamino, carboxylic acid, carboxylic ester, sulfonic acid and phosphonic acid; and optionally substituted heterocyclic radicals; [0032] each of R.sub.3 and R.sub.4 is an atom or radical independently selected from the group consisting of hydrogen; halogen; C.sub.2-4 alkyl; C.sub.2-7 alkenyl; C.sub.2-7 alkynyl; halo C.sub.1-4 alkyl; C.sub.2-4 alkoxy; C.sub.3-10 cycloalkoxy; aryloxy; arylalkyloxy; oxyheterocyclic; heterocyclic-substituted alkyloxy; thio C.sub.2-7 alkyl; thio C.sub.3-10 cycloalkyl; thioaryl; thioheterocyclic; arylalkylthio; heterocyclic-substituted alkylthio; hydroxylamino; acetal; formyl; cyano; carboxylic acid; carboxylic acid esters, thioesters and amides; thiocarboxylic acid; thiocarboxylic acid esters, thioesters and amides; amino; alkylamino; cycloalkylamino; alkenylamino; cycloalkenylamino; alkynylamino; arylamino; arylalkylamino; hydroxyalkylamino; mercaptoalkylamino; heterocyclic amino; heterocyclic-substituted alkylamino; oximino; alkyloximino; hydrazino; alkylhydrazino; phenylhydrazino; cysteinyl acid, esters or amides; aryl substituted with one or more substituents selected from the group consisting of halogen, C.sub.1-4 alkyl, C.sub.2-7 alkenyl, C.sub.2-7 alkynyl, halo C.sub.1-4 alkyl, C.sub.1-4 alkoxy, hydroxyl, sulfhydryl, amino, C.sub.3-10 cycloalkoxy, aryloxy, arylalkyloxy, oxyheterocyclic, heterocyclic-substituted alkyloxy, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, thioaryl, thioheterocyclic, arylalkylthio, heterocyclic-substituted alkylthio, formyl, hydroxylamino, cyano, carboxylic acid or esters or thioesters or amides thereof, thiocarboxylic acid or esters or thioesters or amides thereof, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxylalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino and phenylhydrazino; optionally substituted heterocyclic radicals; aryl or heterocyclic radicals substituted with an aliphatic spacer (linking group) between the pteridine ring and the aryl or heterocyclic radical, whereby said aliphatic spacer is a branched or straight, saturated or unsaturated aliphatic chain of 1 to 4 carbon atoms (such as a C.sub.1-4 alkylene) which may contain one or more functions, atoms or radicals selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkyl-amino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen; branched or straight, saturated or unsaturated aliphatic chain of 1 to 7 carbon atoms containing one or more functions selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid ester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxylalkylamino, mercaptoalkyl-amino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen; or R.sub.4 and R.sub.3 together form an aryl radical being optionally substituted with one or more substituents R.sub.a each independently selected from the group consisting of amino, alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino and heterocyclic-substituted alkylamino, wherein each substituent R.sub.a may further comprise one or more functions selected from the group consisting of carbonyl, amino and carboxyl, and wherein two adjacent substituents R.sub.a may together form an heterocyclic radical; and [0033] at most one of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is hydrogen; [0034] d) if Y.sub.1 and Y.sub.2 are both oxygen and none of R.sub.3 and R.sub.4 is hydrogen, then: [0035] R.sub.2 is a radical selected from the group consisting of C.sub.1-7 alkyl; C.sub.2-7 alkenyl; aryl; alkylaryl; .omega.-hydroxy C.sub.1-7 alkyl; .omega.-epoxy C.sub.1-7 alkyl; .omega.-carboxy C.sub.1-7 alkyl (wherein the carboxy group may be acid, ester, thioester, acid halide or amide); .omega.-cyano C.sub.1-7 alkyl; arylalkyl; arylalkenyl; heterocyclic-substituted alkyl; heterocyclic-substituted alkenyl; groups having the formula --S--R (i.e. wherein a sulfur atom is attached to the nitrogen atom of the pteridine ring) wherein R is a monovalent group selected from the group consisting of C.sub.1-7 alkyl, aryl and C.sub.3-10 cycloalkyl and wherein the said monovalent group is optionally substituted with one or more substituents selected from the group consisting of amino, amino-acid, alkylamino, arylamino, cycloalkylamino, carboxylic acid, carboxylic ester, sulfonic acid and phosphonic acid; and optionally substituted heterocyclic radicals; [0036] R.sub.1 is an atom or radical independently defined as R.sub.2, or is hydrogen; [0037] R.sub.4 is an atom or radical selected from the group consisting of halogen (preferably chloro); C.sub.2-7 alkenyl; C.sub.2-7 alkynyl; C.sub.2-7 haloalkyl; fluoromethyl; C.sub.2-4 alkoxy; C.sub.3-10 cycloalkoxy; aryloxy; arylalkyloxy; oxyheterocyclic; heterocyclic-substituted alkyloxy; thio C.sub.1-7 alkyl; thio C.sub.3-10 cycloalkyl; thioaryl; thioheterocyclic; arylalkylthio; heterocyclic-substituted alkylthio; hydroxyl-amino; acetal; carboxylic acid thioesters and amides; thiocarboxylic acid; thiocarboxylic acid esters, thioesters and amides; sulfhydryl; C.sub.2-7 alkylamino; cycloalkylamino; alkenylamino; cycloalkenylamino; alkynylamino; arylamino; arylalkylamino; hydroxyalkylamino; mercaptoalkylamino; heterocyclic amino; heterocyclic-substituted alkylamino; hydrazino; alkylhydrazino; phenylhydrazino; cysteinyl acid, esters or amides; aryl optionally substituted with one or more substituents selected from the group consisting of halogen, C.sub.1-4 alkyl, C.sub.2-7 alkenyl, C.sub.2-7 alkynyl, halo C.sub.1-7 alkyl, C.sub.1-7 alkoxy, hydroxyl, sulfhydryl, amino, C.sub.3-10 cycloalkoxy, aryloxy, arylalkyloxy, oxyheterocyclic, heterocyclic-substituted alkyloxy, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, thioaryl, thioheterocyclic, arylalkylthio, heterocyclic-substituted alkylthio, formyl, hydroxylamino, cyano, carboxylic acid or esters or thioesters or amides thereof, thiocarboxylic acid or esters or thioesters or amides thereof, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxylalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino and phenylhydrazino; optionally substituted heterocyclic radicals preferably selected from the group consisting of diazepinyl, oxadiazinyl, thiadiazinyl, dithiazinyl, triazolonyl, diazepinonyl, triazepinyl, triazepinonyl, tetrazepinonyl, benzoquinolinyl, benzothiazinyl, benzothiazinonyl, benzoxathiinyl, benzodioxinyl, benzodithiinyl, benzoxaze-pinyl, benzothiazepinyl, benzodiazepinyl, benzodioxepinyl, benzodithiepinyl, benzoxazocinyl, benzothiazocinyl, benzodiazocinyl, benzoxathiocinyl, benzodioxocinyl, benzotrioxepinyl, benzoxathiazepinyl, benzoxadiazepinyl, benzothiadiazepinyl, benzotriazepinyl, benzoxathiepinyl, benzotriazinonyl, benzoxazolinonyl, azetidinonyl, azaspiroundecyl, dithiaspirodecyl, selenazinyl, selenazolyl, selenophenyl, hypoxanthinyl, azahypoxanthinyl, bipyrazinyl, bipyridinyl, oxazolidinyl, diselenopyrimidinyl, benzopyrenyl, benzopyranonyl, benzophenazinyl, benzoquinolizinyl, dibenzocarbazolyl, dibenzoacridinyl, dibenzophenazinyl, dibenzothiepinyl, dibenzooxepinyl, dibenzopyranonyl, dibenzoquinoxalinyl, dibenzothiazepinyl, dibenzoiso-quinolinyl, tetraazaadamantyl, thiatetraazaadamantyl, oxauracil, oxazinyl, dibenzothiophenyl, dibenzofuranyl, oxazolinyl, oxazolonyl, azaindolyl, azolonyl, thiazolinyl, thiazolonyl, thiazolidinyl, thiazanyl, pyrimidonyl, thiopyrimidonyl, thiamorpholinyl, azlactonyl, naphtindazolyl, naphtindolyl, naphtothiazolyl, naphtothioxolyl, naphtoxindolyl, naphtotriazolyl, naphtopyranyl, indolinyl, indolizidinyl, tetrahydrofuryl, oxabicycloheptyl, azabenzimidazolyl, azacycloheptyl, azacyclooctyl, azacyclononyl, azabicyclononyl, tetrahydropyranyl, tetrahydropyronyl, tetrahydroquinoleinyl, tetrahydrothienyl and dioxide thereof, dihydrothienyl dioxide, dioxindolyl, dioxinyl, dioxenyl, dioxazinyl, thioxanyl, thioxolyl, thio-urazolyl, thiotriazolyl, thiopyranyl, thiopyronyl, coumarinyl, quinoleinyl, oxyquinoleinyl, quinuclidinyl, xanthinyl, dihydropyranyl, benzodihydrofuryl, benzothiopyronyl, benzothiopyranyl, benzoxazinyl, benzoxazolyl, benzodioxolyl, benzodioxanyl, benzothiadiazolyl, benzotriazinyl, benzothiazolyl, benzoxazolyl, phenothioxinyl, phenothiazolyl, phenothienyl, phenopyronyl, phenoxazolyl, pyridinyl, dihydropyridinyl, tetrahydropyridinyl, piperidinyl, morpholinyl, thiomorpholinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, tetrazinyl, triazolyl, benzotriazolyl, tetrazolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, oxazolyl, oxadiazolyl, pyrrolyl, furyl, dihydrofuryl, furoyl, hydantoinyl, dioxolyl, dithianyl, dithienyl, dithiinyl, thienyl, indolyl, indazolyl, benzofuryl, benzothienyl, quinolyl, quinazolinyl, quinoxalinyl, carbazolyl, phenoxazinyl, phenothiazinyl, xanthenyl, purinyl, benzothienyl, naphtothienyl, thianthrenyl, pyranyl, pyronyl, benzopyronyl, isobenzofuranyl, chromenyl, phenoxathiinyl, indolizinyl, quinolizinyl, isoquinolyl, phthalazinyl, naphthiridinyl, cinnolinyl, pteridinyl, carbolinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, imidazolinyl, imidazolidinyl, benzimidazolyl, pyrazolinyl, pyrazolidinyl, pyrrolinyl, pyrrolidinyl, piperazinyl, uridinyl, thymidinyl,cytidinyl, azirinyl, aziridinyl, diazirinyl, diaziridinyl, oxiranyl, oxaziridinyl, dioxiranyl, thiiranyl, azetyl, dihydroazetyl, azetidinyl, oxetyl, oxetanyl, thietyl, thietanyl, oxetanonyl, diazabicyclooctyl, diazetyl, diaziridinonyl, diaziridinethionyl, chromanyl, chromanonyl, thiochromanyl, thiochromanonyl, thiochromenyl, benzofuranyl, benzisothiazolyl, benzocarbazolyl, benzochromonyl, benzisoalloxazinyl, benzocoumarinyl, thiocoumarinyl, phenometoxazinyl, phenoparoxazinyl, phentriazinyl, thiodiazinyl, thiodiazolyl, indoxyl, thioindoxyl, benzodiazinyl (e.g. phtalazinyl), phtalidyl, phtalimidinyl, phtalazonyl, alloxazinyl, dibenzopyronyl (i.e. xanthonyl), xanthionyl, isatyl, isopyrazolyl, isopyrazolonyl, urazolyl, urazinyl, uretinyl, uretidinyl, succinyl, succinimido, benzylsultimyl, and benzylsultamyl; aryl or heterocyclic radicals substituted with an aliphatic spacer between the pteridine ring and the aryl or heterocyclic radical, whereby said aliphatic spacer is a branched or straight, saturated or unsaturated aliphatic chain of 1 to 4 carbon atoms which may contain one or more functions, atoms or radicals selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid or ester or thioester or amide, nitro, thio C.sub.1-7 alkyl, thio C.sub.3-10 cycloalkyl, C.sub.1-7 alkylamino, cycloalkylamino, alkenylamino, cycloalkenylamino, alkynylamino, arylamino, arylalkylamino, hydroxyalkylamino, mercaptoalkylamino, heterocyclic amino, hydrazino, alkylhydrazino, phenylhydrazino, sulfonyl, sulfonamido and halogen; branched or straight, saturated or unsaturated aliphatic chain of 2 to 7 carbon atoms containing one or more atoms, functions or radicals selected from the group consisting of carbonyl (oxo), alcohol (hydroxyl), ether, acetal, amino, imino, oximino, alkyloximino, amino-acid, cyano, carboxylic acid ester or amide, nitro, thio C Continue reading... 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