Pyrimido›5,4-D!pyrimidines, Medicaments Comprising These Compounds, Their Use and Processes for Their Preparation

1. A pyrimido›5,4-d!pyrimidines of the general formula ##STR8## in which R.sub.a is a hydrogen atom or an alkyl group, R.sub.b is a phenyl group which is substituted by the radicals R.sub.1 to R.sub.3, wherein R.sub.1 and R.sub.2, which can be identical or different, are each a hydrogen, fluorine, chlorine, bromine or iodine atom, a C.sub.1-6 -alkyl, hydroxyl or C.sub.1-6 alkoxy group, a C.sub.3-7 -cycloalkyl or C.sub.4-7 -cycloalkoxy group, each of which can be substituted by one or two alkyl groups or by an aryl group, a C.sub.2-5 -alkenyl or C.sub.3-5 -alkenyloxy group which is optionally substituted by an aryl group, wherein the vinyl part cannot be linked to the oxygen atom, a C.sub.2-5 -alkynyl or C.sub.3-5 -alkynyloxy group which is optionally substituted by an aryl group, wherein the ethynyl part cannot be linked to the oxygen atom, an aryl, aryloxy, aralkyl, aralkoxy, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, alkylsulphonyloxy, trifluoromethylsulphenyl, trifluoromethylsulphinyl, trifluoromethylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl or aralkylsulphonyl group, a methyl or methoxy group which is substituted by 1 to 3 fluorine atoms, a C.sub.2-4 -alkyl or C.sub.2-4 -alkoxy group which is substituted by 1 to 5 fluorine atoms, a nitro, amino, alkylamino, dialkylamino, C.sub.3-7 -cycloalkylamino, N-alkyl-C.sub.3-7 -cycloalkylamino, arylamino, N-alkylarylamino, aralkylamino or N-alkyl-aralkylamino group, a 4- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 5- to 7-membered alkylenimino groups, in each case one or two methylene groups adjacent to the nitrogen atom can in each case be replaced by a carbonyl group, or in the abovementioned 6- to 7-membered alkylenimino groups, a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkyl-carbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, an (alkylenimino)carbonyl or (alkylenimino)sulphonyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, an alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, arylcarbonylamino, N-alkyl-arylcarbonylamino, arylsulphonylamino, N-alkyl-aryl-sulphonylamino, aralkylcarbonylamino, N-alkylaralkylcarbonylamino, aralkylsulphonylamino, N-alkylaralkylsulphonylamino, perfluoroalkylsulphonylamino, N-alkylperfluoroalkylsulphonylamino, alkylcarbonyl, arylcarbonyl, aralkylcarbonyl, aryl-hydroxymethyl, aralkyl-hydroxymethyl, carboxyl, alkoxycarbonyl, aralkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, arylaminocarbonyl, N-alkyl-arylaminocarbonyl, aralkylaminocarbonyl, N-alkylaralkylaminocarbonyl, N-hydroxy-aminocarbonyl, N-hydroxyalkylaminocarbonyl, N-alkoxy-aminocarbonyl, N-alkoxyalkylaminocarbonyl, cyano, azido, N-cyano-amino or N-cyanoalkylamino group, a sulpho, alkoxysulphonyl, aminosulphonyl, alkylaminosulphonyl, dialkylaminosulphonyl, arylaminosulphonyl, N-alkylarylaminosulphonyl, aralkylaminosulphonyl or N-alkylaralkylaminosulphonyl group, a phosphono, O-alkyl-phosphono, O,O'-dialkyl-phosphono, O-aralkyl-phosphono or O,O'-diaralkyl-phosphono group, an alkyl or alkoxy group which is substituted by R.sub.4, wherein R.sub.4 is a hydroxyl, alkoxy, aryloxy, aralkoxy, amino, alkylamino, dialkylamino, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl, aralkylsulphonyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl or cyano group, a 4- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 5- to 7-membered alkylenimino groups, in each case one or two methylene groups adjacent to the nitrogen atom can be replaced by a carbonyl group, or in the abovementioned 6- to 7-membered alkylenimino groups, a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-alkylsulphonylimino, N-aryl-imino or N-aralkyl-imino group, or an (alkylenimino)carbonyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, R.sub.3 is a hydrogen, fluorine, chlorine or bromine atom, an alkyl, alkoxy or trifluoromethyl group or R.sub.2 together with R.sub.3, if these are bonded to adjacent carbon atoms, is a methylenedioxy group which is optionally substituted by one or two alkyl groups, an n-C.sub.3-6 -alkylene group which is optionally substituted by one or two alkyl groups, or a 1,3-butadiene-1,4-diylene group which is optionally substituted by one or two fluorine, chlorine, bromine or iodine atoms or by one or two hydroxyl, alkyl, alkoxy, trifluoromethyl or cyano groups, wherein the substituents can be identical or different, or R.sub.a together with R.sub.1, if R.sub.1 is in the o-position relative to the nitrogen atom which is substituted by R.sub.a, is an n-C.sub.2-4 -alkylene group which is optionally substituted by one or two alkyl groups, and R.sub.c is C.sub.3-7 -cycloalkyl, C.sub.3-7 -cycloalkyl-C.sub.1-3 -alkyl, aralkyl, hydroxyl, aryloxy, aralkoxy, mercapto, C.sub.1-8 -alklsulphenyl, C.sub.1-8 -alkylsulphinyl, C.sub.1-8 -alkylsulphonyl, C.sub.4-7 cycloalkylsulphenyl, C.sub.4-7 -cycloalkylsulphinyl, C.sub.-4-7 -cycloalkylsulphonyl, C.sub.3-7 -cycloalkyl-C.sub.1-3 -alkylsulphenyl, C.sub.3-7 -cycloalkyl-C.sub.1-3 -alkylsulphinyl, C.sub.3-7 -cycloalkyl-C.sub.1-3 -alkylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl or aralkylsulphonyl group, a C.sub.1-8 -alkoxy group substituted by an alkoxycarbonyl, cyano, carboxyl, aminocarbonyl, alkylaminocarbonyl or dialkylaminocarbonyl group, a C.sub.2-8 -alkoxy group substituted by a hydroxyl, alkoxy, hydroxy-C.sub.2-4 -alkylamino, amino, alkylamino, dialkylamino, alkylcarbonylamino, N-alkyl-N-(alkylcarbonyl)amino, alkylsulphonylamino, N-alkyl-N-(alkylsulphonyl)amino, alkoxycarbonylamino or N-alkyl-N-(alkoxycarbonyl)amino group, by a 5- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 5- to 7-membered alkylenimino groups, in each case one or two methylene groups adjacent to the nitrogen atom can be replaced by a carbonyl group, and additionally in the abovementioned 6- to 7-membered alkylenimino groups, a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-formyl-imino, N-dialkylaminocarbonyl-imino, N-alkoxy-carbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, a C.sub.3-8 -alkoxy group substituted by two hydroxyl or alkoxy groups, a C.sub.1-8 -alkoxy group substituted by a C.sub.3-7 -cycloalkyl group wherein in each case the cycloalkyl residue can be substituted by 1 to 4 alkyl groups, and wherein, in the abovementioned C.sub.4-7 -cycloalkyl residues, in each case a methylene group can be replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonylimino, N-alkoxycarbonyl-imino, N-alkylsulphonyl-imino, N-arylimino or N-aralkyl-imino group, a C.sub.4-7 -cycloalkoxy group which is optionally substituted by one or two hydroxyl groups or by an alkoxy, alkoxycarbonyl, cyano, carboxyl, amino-carbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, hydroxy-C.sub.2-4 -alkylamino, amino, alkylamino, dialkylamino, alkylcarbonyl-amino, N-alkyl-N-(alkylcarbonyl)amino, alkylsulphonylamino, N-alkyl-N-(alkylsulphonyl)amino, alkoxycarbonylamino or N-alkyl-N-(alkoxycarbonyl)amino group, wherein, in the abovementioned C.sub.5-7 -cycloalkoxy groups, in each case a methylene group can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-alkoxycarbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, a C.sub.3-8 -alkenyloxy group which is optionally substituted by an aryl group or C.sub.3-7 -cycloalkyl group, wherein the vinyl part cannot be linked to the oxygen atom, a C.sub.3-8 -alkynyloxy group which is optionally substituted by an aryl group or C.sub.3-7 -cycloalkyl group, wherein the ethynyl part cannot be linked to the oxygen atom, a 4- to 8-membered alkylenimino group which is option-ally substituted by 1 to 4 alkyl groups or 1 to 2 aryl groups, and which can additionally be substituted by the radical R.sub.5, wherein R.sub.5 is an aryl, aralkyl, carboxyl, alkoxycacarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, cyano, hydroxyl, alkoxy, aryloxy, aralkoxy, alkylcarbonyloxy, arylcarbonyloxy, amino, alkylamino, hydroxy-C.sub.2-4 -alkylamino, dialkylamino, cyano-amino, formylamino, N-(alkyl)-N-(hydroxy-C.sub.2-4 -alkyl)amino or bis-(hydroxy-C.sub.2-4 -alkyl)amino group, an (alkylenimino)carbonyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkyl-carbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, a 4- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups or a hydroxy-alkyl group, wherein, in the abovementioned 5- to 7-membered alkylenimino groups, in each case one or two methylene groups adjacent to the nitrogen atom can be replaced by a carbonyl group, a 6- or 7-membered alkyleneimino group which is optionally substituted by 1 to 4 alkyl groups or a hydroxyalkyl group, whereby in each case a methylene group in the 4-position of the alkyleneimino residue is replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-alkyl-sulphonylimino, N-aryl-imino or N-aralkyl-imino group, and additionally in the alkyleneimino residue of the abovementioned groups in each case one or two of the methylene groups adjacent to the nitrogen atoms can be replaced by a carbonyl group, a 4- to 7-membered alkylenimino group which is substituted by a hydroxyl, alkoxy, amino, alkylamino, dialkylamino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonyl-amino or hydroxyalkyl group, an alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, arylcarbonylamino, N-alkyl-arylcarbonylamino, arylsulphonylamino, N-alkyl-arylsulphonylamino, aralkylcarbonylamino, N-alkyl-aralkylcarbonylamino, aralkylsulphonylamino, N-alkyl-aralkylsulphonylamino, alkoxycarbonylamino, N-alkyl-alkoxycarbonylamino, aralkoxycarbonylamino or N-alkyl-aralkoxycarbonylamino group, a (NR.sub.7 R.sub.8)CONR.sub.6 -- or (NR.sub.7 R.sub.8)SO.sub.2 NR.sub.6 -- group, in which R.sub.6, R.sub.7 and R.sub.8, which can be identical or different, are each a hydrogen atom or an alkyl group or R.sub.6 and R.sub.7 together are an n-C.sub.2-4 -alkylene group and R.sub.8 is a hydrogen atom or an alkyl group, a carboxyalkyl, alkoxycarbonylalkyl, aminocarbonyl-alkyl, alkylaminocarbonylalkyl or dialkylaminocarbonylalkyl group, an (alkylenimino)carbonylalkyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino or N-alkyl-imino group, a (carboxyalkyl)oxy, (alkoxycarbonylalkyl)oxy, (aminocarbonylalkyl)oxy, (alkylaminocarbonylalkyl)oxy or (dialkylaminocarbonylalkyl)oxy group, an ›(alkylenimino)carbonylalkyl!oxy group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino or N-alkyl-imino group, a cyanoalkyl, hydroxyalkyl, alkoxyalkyl, aryloxyalkyl, aminoalkyl, alkylaminoalkyl or dialkylaminoalkyl group, an (alkylenimino)alkyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino or N-alkyl-imino group, an alkylcarbonylaminoalkyl, N-alkyl-alkylcarbonylaminoalkyl, alkylsulphonylaminoalkyl, N-alkyl-alkylsulphonylaminoalkyl, arylcarbonylaminoalkyl, N-alkyl-arylcarbonylaminoalkyl, arylsulphonylaminoalkyl, N-alkyl-arylsulphonylaminoalkyl, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl, aralkylsulphonyl, alkylsulphenylalkyl, alkylsulphinylalkyl, alkylsulphonylalkyl, arylsulphenylalkyl, arylsulphinylalkyl or arylsulphonylalkyl group or a C.sub.3-7 -cycloalkyl group, wherein, in a C.sub.5-7 -cycloalkyl group, a methylene group can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino or N-alkylimino group, or R.sub.c is a 6- to 8-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups or an aryl group and can additionally be substituted by the radical R.sub.5, wherein, in the abovementioned alkylenimino groups, in each case a methylene group in the 4-position is replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, N-oxido-N-alkylimino or R.sub.9 N group, wherein R.sub.9 is a hydrogen atom, an alkyl, hydroxy-C.sub.2-4 -alkyl, alkoxy-C.sub.2-4 -alkyl, amino-C.sub.2-4 -alkyl, alkylamino-C.sub.2-4 -alkyl, dialkylamino-C.sub.2-4 -alkyl, (hydroxy-C.sub.2-4 -alkoxy)-C.sub.2-4 -alkyl, aminocarbonylalkyl, alkylaminocarbonylalkyl, dialkylaminocarbonylalkyl, aryl, aralkyl, formyl, alkylcarbonyl, alkylsulphonyl, arylcarbonyl, arylsulphonyl, aralkylcarbonyl, aralkylsulphonyl, alkoxycarbonyl, cyano, aminocarbonyl, alkylaminocarbonyl or dialkylaminocarbonyl group or an (alkylenimino)carbonyl group which has in each case 4 to 7 ring atoms in the alkylenimino part, wherein, in a 6- to 7-membered alkylenimino part, a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino or N-alkyl-imino group, or R.sub.c is a 1-pyrrolidinyl group which is optionally substituted by 1 to 4 alkyl groups and in which two hydrogen atoms on the carbon skeleton are replaced by a straight-chain alkylene bridge, wherein this bridge contains 2 to 6 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 1 to 5 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 to 4 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by an atom, wherein the abovementioned 1-pyrrolidinyl groups can additionally be substituted by the radical R.sub.5, which is defined as mentioned above, a 1-piperidinyl or 1-azacyclohept-1-yl group which is optionally substituted by 1 to 4 alkyl groups and in which two hydrogen atoms on the carbon skeleton are replaced by a straight-chain alkylene bridge, wherein this bridge contains 2 to 6 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 1 to 5 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 1 to 4 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by an atom, or contains 1 to 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by two atoms, wherein the abovementioned 1-piperidinyl and 1-azacyclohept-1-yl groups can additionally be substituted by the radical R.sub.5, which is defined as mentioned above, a 1-pyrrolidinyl group which is optionally substituted by 1 to 4 alkyl groups and in which two hydrogen atoms in the 3-position are substituted by a --O--CH.sub.2 CH.sub.2 --O-- or --O--CH.sub.2 CH.sub.2 CH.sub.2 --O-- group, a 1-piperidinyl or 1-azacyclohept-1-yl group which is optionally substituted by 1 to 4 alkyl groups and in which, in the 3-position or in the 4-position, in each case two hydrogen atoms are replaced by a --O--CH.sub.2 CH.sub.2 --O-- or --O--CH.sub.2 CH.sub.2 CH.sub.2 --O-- group, a group of the formula ##STR9## in which m and n, which can be identical or different, are the numbers 1 to 3 or m is the number 0 and n is the number 2, 3 or 4, wherein, additionally, the above benzo part can be mono- or disubstituted by fluorine, chlorine, bromine or iodine atoms or by alkyl, trifluoromethyl, hydroxyl, alkoxy or cyano groups and the above saturated cyclic imino part can be mono- or disubstituted by 1 or 2 alkyl groups, wherein the substituents can in each case be identical or different, or an (R.sub.10 NR.sub.11) group, in which R.sub.10 and R.sub.11, which can be identical or different, are each a hydrogen atom, a C.sub.1-16 -alkyl group, which can be substituted by 1 or 2 aryl or C.sub.3-7 -cycloalkyl groups, by a carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, hydroxy-C.sub.2-4 -alkylaminocarbonyl, cyano, hydroxyl, alkoxy, aryloxy, aralkoxy, C.sub.2-4 -alkylenedioxy, alkylcarbonyloxy, arylcarbonyloxy, formylamino, amino, alkylamino or dialkylamino group, by an (alkylenimino)carbonyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in a 6- or 7-membered alkylenimino residue, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkylimino, N-alkylcarbonyl-imino, N-alkylsulphonyl-imino, N-arylimino or N-aralkyl-imino group, by a 4- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- or 7-membered alkylenimino groups, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl or R.sub.9 N group, wherein R.sub.9 is as defined above, and additionally in the abovementioned 5- to 7-membered alkylenimino groups, in each case one or two methylene groups adjacent to the nitrogen atoms can be replaced by a carbonyl group, by an alkylsulphonylamino, N-alkyl-alkylsulphonylamino, arylcarbonylamino, N-alkyl-arylcarbonyl-amino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, arylsulphonylamino, N-alkyl-arylsulphonylamino, aralkylcarbonylamino, N-alkylaralkylcarbonylamino, aralkylsulphonylamino, N-alkyl-aralkylsulphonylamino, alkoxycarbonylamino, N-alkyl-alkoxycarbonylamino, aralkoxycarbonylamino or N-alkyl-aralkoxycarbonylamino group, by an (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- or (R.sub.8 NR.sub.7)--SO.sub.2 --NR.sub.6 -- group, wherein R.sub.6, R.sub.7 and R.sub.8 are as defined above, by an alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, arylsulphenyl, arylsulphinyl. arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl or aralkylsulphonyl group, by a C.sub.4-7 -cycloalkyl group which is substituted by R.sub.5 and optionally additionally by 1 to 4 alkyl groups, wherein R.sub.5 is as defined above, by a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which a methylene group is replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, or NR.sub.9 group, or by a fluorine, chlorine, bromine or iodine atom, a C.sub.2-10 -alkyl group substituted by 2 or 3 fluorine atoms, a C.sub.3-10 -alkyl group substituted by 4 or 5 fluorine atoms, a methyl group which is substituted by a 1,4,7,10-tetraoxacyclododecyl, 1,4,7,10,13-pentaoxacyclopentadecyl or a 1,4,7,10,13,16-hexaoxacyclooctadecyl group, a C.sub.3-10 -alkyl group which is substituted by 2 to 5 hydroxyl or alkoxy groups, a C.sub.2-6 -alkyl group which is substituted by an aryl group and a hydroxyl group and can additionally be substituted by an amino, alkylamino, dialkylamino, hydroxyl or alkoxy group, a C.sub.3-6 -alkyl group which is substituted by an amino, alkylamino, dialkylamino, alkylcarbonylamino or alkoxycarbonylamino group and additionally by a hydroxyl or alkoxy group, an alkenyl or alkynyl group which has in each case 3 to 6 carbon atoms and is optionally substituted by an aryl group or C.sub.3-7 -cycloalkyl group, wherein the vinyl or ethynyl part cannot be linked to the nitrogen atom, a C.sub.2-4 -alkyl group which is substituted by a C.sub.2-4 -alkoxy group which is substituted in the .omega.-position by a hydroxyl or alkoxy group, an aryl group, a cyclopropyl group which can be substituted by 1 or 2 alkyl groups, by an aryl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl or dialkylaminocarbonyl group or by an (alkylenimino)carbonyl group which has in each case 4 to 7 ring atoms in the alkylenimino part and is optionally substituted by 1 to 4 alkyl groups, wherein, in the abovementioned 6- or 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, imino, N-alkylimino, N-alkylcarbonyl-imino, N-alkylsulphonyl-imino, N-aryl-imino or N-aralkyl-imino group, a C.sub.4-7 -cycloalkyl group which is optionally substituted by 1 to 4 alkyl groups and can additionally be substituted by R.sub.5, which is as defined above, a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 to 2 alkyl groups and is additionally substituted by an N,N-dialkyl-N-oxido-amino group, a C.sub.5-7 -cycloalkenyl group which is optionally substituted by 1 to 4 alkyl groups, wherein the vinyl part cannot be linked to the nitrogen atom of the (R.sub.11 NR.sub.10)-- group, a C.sub.4-7 -cycloalkyl group which is optionally substituted by 1 to 4 alkyl groups and can additionally be substituted by R.sub.5, wherein, in the cycloalkyl part, a methylene group is replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, N-alkyl-N-oxido-imino or R.sub.9 N group, wherein R.sub.5 and R.sub.9 are as defined above, a C.sub.5-7 -cycloalkyl or C.sub.5 -C.sub.7 -cycloalkylalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which in each case a methylene group in the cycloalkyl part is replaced by a carbonyl group, a cyclopentyl or cyclopentylalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which in each case two hydrogen atoms in the cyclopentyl part are replaced by a straight-chain alkylene bridge, wherein this bridge contains 2 to 6 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 1 to 5 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 to 4 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by a carbon atom, wherein the abovementioned rings can additionally be substituted by the radical R.sub.5, which is as defined above, a cyclohexyl, cyclohexylalkyl, cycloheptyl or cycloheptylalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which in each case two hydrogen atoms in the cycloalkyl part are replaced by a straight-chain alkylene bridge, wherein this bridge contains 2 to 6 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 1 to 5 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 1 to 4 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by a carbon atom, or contains 1 to 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by two carbon atoms, wherein the abovementioned rings can additionally be substituted by the radical R.sub.5, which is as defined above, a 3-cyclohexen-1-yl or 3-cyclohexen-1-yl-alkyl group which is optionally substituted by 1 to 4 alkyl groups and in which two hydrogen atoms in the 2,5-position in the cyclohexenyl part are replaced by an n-C.sub.1-3 -alkylene bridge, a 3-quinuclidinyl, 4-quinuclidinyl, 2-quinuclidinyl-alkyl, 3-quinuclidinyl-alkyl, 4-quinuclidinyl-alkyl, azabicyclo›2.2.1!hept-4-yl, azabicyclo›2.2.1!hept-4-yl-alkyl or adamantyl group, or R.sub.10 is a hydrogen atom or an alkyl group and R.sub.11 is a hydroxyl, alkoxy or cyano group, their tautomers, their stereoisomers and their salts, wherein, unless mentioned otherwise, the aryl parts mentioned in the definition of the abovementioned radicals is to be understood as meaning a phenyl group which can be in each case be monosubstituted by R.sub.12, mono-, di- or trisubstituted by R.sub.13 or monosubstituted by R.sub.12 and additionally mono- or disubstituted by R.sub.13, wherein the substituents can be identical or different, and R.sub.12 is a cyano, carboxyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkoxycarbonyl, alkylcarbonyl, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, alkylsulphonyloxy, perfluoroalkyl, perfluoroalkoxy, nitro, amino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylamino, dialkylamino, hydroxy-C.sub.2-4 -alkylamino, N-alkyl-(hydroxy-C.sub.2-4 -alkyl)amino, bis-(hydroxy-C.sub.2-4 -alkyl)amino, phenylalkylcarbonylamino, phenylcarbonylamino, alkylsulphonylamino, phenylalkylsulphonylamino, phenylsulphonylamino, N-alkyl-phenylalkylcarbonylamino, N-alkyl-phenylcarbonylamino, N-alkyl-alkylsulphonylamino, N-alkyl-phenylalkylsulphonylamino, N-alkyl-phenylsulphonylamino, aminosulphonyl, alkylaminosulphonyl, dialkylaminosulphonyl, (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- or (R.sub.8 NR.sub.7)--SO.sub.2 --NR.sub.6 -- group, wherein R.sub.6, R.sub.7 and R.sub.8 are as defined above, a 5- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups or a hydroxyalkyl group, wherein, in the abovementioned 6- to 7-membered alkylenimino groups, in each case a methylene group in the 4-position can be replaced by an oxygen atom or an R.sub.9 N group, wherein R.sub.9 is as defined above, a 5- to 7-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups or a hydroxyalkyl group, wherein in each case one or two methylene groups adjacent to the nitrogen atom are in each case replaced by a carbonyl group, and R.sub.13 is an alkyl, hydroxyl or alkoxy group or a fluorine, chlorine, bromine or iodine atom, wherein two radicals R.sub.13, if these are bonded to adjacent carbon atoms, can also be an alkylene group having 3 to 6 carbon atoms, a 1,3-butadiene-1,4-diylene group or a methylenedioxy group, and, unless mentioned otherwise, the abovementioned alkyl, alkylene and alkoxy parts in each case contain 1 to 4 carbon atoms.

2. Pyrimido›5,4-d!pyrimidines of the general formula I according to claim 1, with the proviso that, unless mentioned otherwise, each carbon atom in the alkylene or cycloalkylene parts mentioned in claim 1 which is bonded to a nitrogen, oxygen or sulphur atom cannot be bonded to a further halogen, nitrogen, oxygen or sulphur atom, their tautomers, their stereoisomers and their salts.

3. Pyrimido›5,4-d!pyrimidines according to claim 1 or 2, in which R.sub.a is a hydrogen atom or an alkyl group, R.sub.b is a phenyl group which is substituted by the radicals R.sub.1 to R.sub.3, wherein R.sub.1 is a hydrogen, fluorine, chlorine, bromine or iodine atom, a C.sub.1-6 -alkyl, hydroxyl or C.sub.1-6 -alkoxy group, a C.sub.3-6 -cycloalkyl or C.sub.5-6 -cycloalkoxy group, a C.sub.2-5 -alkenyl or C.sub.3-5 -alkenyloxy group, wherein the vinyl part cannot be linked to the oxygen atom, a C.sub.2-5 -alkynyl or C.sub.3-5 -alkynyloxy group, wherein the ethynyl part cannot be linked to the oxygen atom, an aryl, aryloxy, aralkyl, aralkoxy, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, alkylsulphonyloxy, trifluoromethylsulphenyl, trifluoromethylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl or aralkylsulphonyl group, a methyl or methoxy group which is substituted by 1 to 3 fluorine atoms, a C.sub.2-4 -alkyl or C.sub.2-4 -alkoxy group which is substituted by 1 to 5 fluorine atoms, a nitro, amino, alkylamino, dialkylamino, C.sub.3-6 -cycloalkylamino, N-alkyl-C.sub.3-6 -cycloalkylamino, arylamino, N-alkylarylamino, aralkylamino or N-alkyl-aralkylamino group, a 5- to 7-membered alkylenimino group, wherein in each case one or two methylene groups adjacent to the nitrogen atom can in each case be replaced by a carbonyl group or, in the abovementioned 6- to 7-membered alkylenimino groups, a methylene group in the 4-position can be replaced by an oxygen atom or by an imino or N-alkyl-imino group, an (alkylenimino) carbonyl or (alkylenimino) sulphonyl group having in each case 5 to 7 ring atoms in the alkylenimino part, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen atom or by an imino or N-alkyl-imino group, an alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, arylcarbonylamino, N-alkyl-arylcarbonylamino, arylsulphonylamino, N-alkyl-arylsulphonylamino, aralkylcarbonylamino, N-alkyl-aralkylcarbonylamino, aralkylsulphonylamino, N-alkyl-aralkylsulphonylamino, trifluoromethylsulphonylamino, N-alkyl-trifluoromethylsulphonylamino, alkylcarbonyl, arylcarbonyl, aralkylcarbonyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, arylaminocarbonyl, N-alkyl-arylaminocarbonyl, aralkylaminocarbonyl, N-alkyl-aralkyl-aminocarbonyl, N-hydroxy-aminocarbonyl, N-hydroxy-alkyl-aminocarbonyl, N-alkoxy-aminocarbonyl, N-alkoxy-alkyl-aminocarbonyl, cyano, azido, N-cyano-amino or N-cyano-alkylamino group, a sulpho, aminosulphonyl, alkylaminosulphonyl, dialkylaminosulphonyl, arylaminosulphonyl, N-alkyl-arylaminosulphonyl, aralkylaminosulphonyl or N-alkyl-aralkylaminosulphonyl group, a phosphono, O-alkyl-phosphono, O,O'-dialkyl-phosphono or O,O'-diaralkyl-phosphono group, an alkyl or alkoxy group which is substituted by R.sub.4, wherein R.sub.4 is a hydroxyl, alkoxy, aryloxy, amino, alkylamino, dialkylamino, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl or cyano group or an (alkylenimino)carbonyl group having in each case 5 to 7 ring atoms in the alkylenimino part, wherein, in the abovementioned 6- to 7-membered alkylenimino parts, in each case a methylene group in the 4-position can be replaced by an oxygen atom or by an imino or N-alkyl-imino group, R.sub.2 is a hydrogen, fluorine, chlorine or bromine atom or an alkyl, trifluoromethyl, hydroxyl, alkoxy, amino, alkylamino, dialkylamino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino N-alkyl-alkylsulphonylamino, trifluoromethylsulphonylamino, N-alkyl-trifluoromethylsulphonylamino or cyano group and R.sub.3 is a hydrogen, fluorine, chlorine or bromine atom or an alkyl, trifluoromethyl or alkoxy group, or R.sub.2 together with R.sub.3, if these are bonded to adjacent carbon atoms, is a methylenedioxy group which is optionally substituted by one or two alkyl groups, an n-C.sub.3-6 -alkylene group which is optionally substituted by one or two alkyl groups, or a 1,3-butadiene-1,4-diylene group which is optionally substituted by a fluorine, chlorine or bromine atom or by a hydroxyl, alkyl, alkoxy, trifluoromethyl or cyano group, or R.sub.a together with R.sub.1, if R.sub.1 is in the o-position relative to the nitrogen atom substituted by R.sub.a, is an n-C.sub.2-3 -alkylene group, and R.sub.c is an aralkyl, mercapto, alkylsulphenyl, alkylsulphinyl or alkylsulphonyl group, a hydroxyl, aryloxy or aralkoxy group, a C.sub.1-6 -alkoxy group, which is substituted by an alkoxycarbonyl, cyano, carboxyl, aminocarbonyl, alkylaminocarbonyl or dialkylaminocarbonyl group, a C.sub.2-6 -alkoxy group substituted by a hydroxyl, alkoxy, hydroxy-C.sub.2-4 -alkylamino, amino, alkylamino, dialkylamino, alkylcarbonylamino, alkylsulphonylamino or alkoxycarbonylamino group, or by a 5- to 7-membered alkylenimino group which is optionally substituted by 1 to 2 alkyl groups, wherein, in the abovementioned 5- to 7-membered alkylenimino groups, in each case one or two methylene groups adjacent to the nitrogen atom can in each case be replaced by a carbonyl group, or in the abovementioned 6- to 7-membered alkylenimino groups, a methylene group in the 4-position can be replaced by an oxygen atom or by a carbonyl, imino, alkyl-imino, alkylcarbonyl-imino, alkoxycarbonyl-imino, alkylsulphonyl-imino, formyl-imino, dialkylaminocarbonyl-imino, aryl-imino or aralkyl-imino group, a C.sub.3-6 -alkoxy group substituted by two hydroxyl or alkoxy groups, an alkoxy group which is substituted by a C.sub.3-7 -cycloalkyl group wherein the cycloalkyl residue in each case can be substituted by one or two alkyl groups and wherein, in the abovementioned C.sub.4-7 -cycloalkyl residues, in each case a methylene group can be replaced by an oxygen atom, or by an imino, N-alkyl-imino, N-alkylcarbonyl-imino, N-alkoxycarbonyl-imino or N-aryl-imino group, a C.sub.4-7 -cycloalkoxy group which is optionally substituted by a hydroxyl, alkoxy, alkoxycarbonyl, cyano, carboxyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, hydroxy-C.sub.2-4 -alkylamino, amino, alkylamino, dialkylamino, alkylcarbonyl-amino, alkylsulphonylamino or alkoxycarbonylamino group, a C.sub.5-7 -cycloalkoxy group, wherein, in the abovementioned cyclopentyloxy group, in each case a methylene group in the 3-position, and in the abovementioned C.sub.6-7 -cycloalkoxy groups, in each case a methylene group in the 3- or 4-position is replaced by an oxygen atom or by an imino, alkyl-imino, alkylcarbonyl-imino, alkoxycarbonyl-imino, alkylsulphonyl-imino, aryl-imino or aralkyl-imino group, a C.sub.3-6 -alkenyloxy group, wherein the vinyl part cannot be linked to the oxygen atom, a C.sub.3-6 -alkynyloxy group, wherein the ethynyl part cannot be linked to the oxygen atom, a 4- to 8-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups or an aryl group and can additionally be substituted by the radical R.sub.5, wherein R.sub.5 is an aryl, aralkyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl , piperidinocarbonyl, morpholinocarbonyl, piperazinocarbonyl, 4-alkyl-piperazinocarbonyl, cyano, hydroxyl, alkoxy, aryloxy, amino, alkylamino, dialkylamino, hydroxy-C.sub.2-4 -alkylamino, N-alkyl-hydroxy-C.sub.2-4 -alkylamino, di-(hydroxy-C.sub.2-4 -alkyl)amino, formylamino, cyanoamino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkoxycarbonylamino, N-alkyl-alkoxycarbonyl-amino, alkylsulphonylamino, N-alkyl-alkyl-sulphonylamino, arylcarbonylamino, N-alkyl-arylcarbonylamino, arylsulphonyl-amino, N-alkyl-arylsulphonylamino, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, alkylaminocarbonylalkyl, dialkylaminocarbonylalkyl, pyrrolidinocarbonylalkyl; piperidinocarbonylalkyl, morpholinocarbonylalkyl, piperazinocarbonylalkyl, 4-alkyl-piperazinocarbonylalkyl, cyanoalkyl, hydroxyalkyl, alkoxyalkyl, aryloxyalkyl, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, alkylcarbonylaminoalkyl, N-alkyl-alkylcarbonylaminoalkyl, alkylsulphonylaminoalkyl, N-alkyl-alkylsulphonylaminoalkyl, arylcarbonylaminoalkyl, N-alkyl-arylcarbonylaminoalkyl, arylsulphonylaminoalkyl, N-alkyl-arylsulphonylaminoalkyl, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, alkylsulphenylalkyl, alkylsulphinylalkyl, alkylsulphonylalkyl, arylsulphenylalkyl, arylsulphinylalkyl, arylsulphonylalkyl, carboxyalkoxy, alkoxycarbonylalkoxy, aminocarbonylalkoxy, alkylaminocarbonylalkoxy, dialkylaminocarbonylalkoxy, pyrrolidinocarbonyl-alkoxy, piperidinocarbonylalkoxy, morpholinocarbonylalkoxy or an (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- group, wherein, R.sub.6, R.sub.7 and R.sub.8, which can be identical or different, are each a hydrogen atom or an alkyl group, or R.sub.6 and R.sub.7 together are an n-C.sub.2-3 -alkylene group and R.sub.8 is a hydrogen atom or an alkyl group, a pyrrolidino, piperidino, morpholino, piperazino, 4-alkylpiperazino or 4-alkoxycarbonylpiperazino group, optionally substituted by one or two alkyl groups or a hydroxymethyl group, wherein, in the heterocyclic residue of the abovementioned groups, in each case one or two of the methylene groups adjacent to the nitrogen atoms can be replaced by a carbonyl group, or R.sub.c is a 6- to 8-membered alkylenimino group which is optionally substituted by 1 to 4 alkyl groups or by an aryl group and can additionally be substituted by the radical R.sub.5, wherein, in the abovementioned alkylenimino groups, in each case a methylene group in the 4-position is replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, N-oxido-N-alkylimino or R.sub.9 N group, wherein R.sub.9 is a hydrogen atom or an alkyl, hydroxy-C.sub.2-4 -alkyl, alkoxy-C.sub.2-4 -alkyl, hydroxy-C.sub.2-4 -alkoxy-C.sub.2-4 -alkyl, aminocarbonylalkyl, alkylaminocarbonylalkyl, dialkylaminocarbonylalkyl, amino-C.sub.2-4 -alkyl, alkylamino-C.sub.2-4 -alkyl, dialkylamino-C.sub.2-4 -alkyl, aryl, aralkyl, formyl, alkylcarbonyl, alkylsulphonyl, arylcarbonyl, arylsulphonyl, aralkylcarbonyl, aralkylsulphonyl, alkoxycarbonyl, cyano, aminocarbonyl, alkylaminocarbonyl or dialkylaminocarbonyl group, or R.sub.c is a 1-pyrrolidinyl group which is optionally substituted by 1 or 2 alkyl groups and in which two hydrogen atoms on the carbon skeleton are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by an atom, a 1-piperidinyl or 1-azacyclohept-1-yl group which is optionally substituted by 1 or 2 alkyl groups and in which two hydrogen atoms on the carbon skeleton are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by an atom, or contains 1 or 2 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by two atoms, a 1-pyrrolidinyl group in which two hydrogen atoms in the 3-position are replaced by a --O--CH.sub.2 CH.sub.2 --O-- or --O--CH.sub.2 CH.sub.2 CH.sub.2 --O-- group, a 1-piperidinyl or 1-azacyclohept-1-yl group in which two hydrogen atoms in the 3-position or in the 4-position are replaced by a --O--CH.sub.2 CH.sub.2 --O-- or --O--CH.sub.2 CH.sub.2 CH.sub.2 --O-- group, a 2-isoindolinyl, 1,2,3,4-tetrahydro-isoquinolin-2-yl or 2,3,4,5-tetrahydro-1H-3-benzazepin-3-yl group, wherein the benzo part of the abovementioned groups can in each case be substituted by a fluorine, chlorine, bromine or iodine atom, by a trifluoromethyl group or by one or two alkyl or alkoxy groups, or a (R.sub.10 NR.sub.11)-- group, in which R.sub.10 is a hydrogen atom or a C.sub.1-8 -alkyl group, which can be substituted from position 2 by a hydroxyl or alkoxy group, R.sub.11 is a hydrogen atom, a C.sub.1-10 -alkyl group, which can be substituted by an aryl, C.sub.3-7 -cycloalkyl, hydroxyl, alkoxy, aryloxy, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, hydroxy-C.sub.2-4 -alkylaminocarbonyl, cyano, formylamino, amino, alkylamino or dialkylamino group, by a pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, piperazinocarbonyl or 4-alkyl-piperazinocarbonyl group, by a 5- to 7-membered alkylenimino group which is optionally substituted by 1 or 2 alkyl groups, wherein, in the abovementioned 6- or 7-membered alkylenimino residues, in each case a methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl or R.sub.9 N group, wherein R.sub.9 is as defined above, by a pyrrolidino, piperidino, piperazino or 4-alkylpiperazino group, wherein in each case one or two of the methylene groups adjacent to the nitrogen atoms are replaced by a carbonyl group, by an alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, arylcarbonylamino, N-alkyl-arylcarbonylamino, arylsulphonylamino, N-alkyl-arylsulphonylamino, aralkylcarbonylamino, N-alkyl-aralkylcarbonylamino, aralkylsulphonylamino, N-alkyl-aralkylsulphonylamino, alkoxycarbonylamino or N-alkyl-alkoxycarbonylamino group, by an (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- group, wherein R.sub.6 to R.sub.8 are as defined above, by an alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, arylsulphenyl, arylsulphinyl, arylsulphonyl, aralkylsulphenyl, aralkylsulphinyl or aralkylsulphonyl group or by a C.sub.5-7 -cycloalkyl group in which a methylene group is replaced by an oxygen atom or by an imino or alkylimino group, a C.sub.2-4 -alkyl group substituted by a chlorine atom or by one to three fluorine atoms, a methyl group which is substituted by a 1,4,7,10-tetraoxacyclododecyl, 1,4,7,10,13-pentaoxacyclopentadecyl or a 1,4,7,10,13,16-hexaoxacyclooctadecyl group, a C.sub.3-10 -alkyl group which is substituted by 2 to 5 hydroxyl groups, a C.sub.2-6 -alkyl group which is substituted by a hydroxyl and additionally by an aryl group and which can optionally additionally be substituted by a hydroxyl or alkoxy group, a C.sub.3-6 -alkyl group which is substituted by a hydroxyl and additionally by an amino, alkylamino or dialkylamino group, an alkenyl or alkynyl group which has in each case 3 to 6 carbon atoms and is optionally substituted by an aryl group, wherein the vinyl or ethynyl part cannot be linked to the nitrogen atom, a C.sub.2-4 -alkyl group, which is substituted by a C.sub.2-4 -alkoxy group, which is substituted in the e-position by a hydroxyl or alkoxy group, an aryl group, a cyclopropyl group, which can be substituted by 1 or 2 alkyl groups or by an aryl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, piperazinocarbonyl or 4-alkyl-piperazinocarbonyl group, a C.sub.4-7 -cycloalkyl group which is optionally substituted by 1 or 2 alkyl groups and can additionally be substituted by R.sub.5, wherein R.sub.5 is as defined above, a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 or 2 alkyl groups and is additionally substituted by an N,N-dialkyl-N-oxido-amino group, a C.sub.5-7 -cycloalkenyl group which is optionally substituted by 1 or 2 alkyl groups, wherein the vinyl part cannot be linked to the nitrogen atom of the (R.sub.11 NR.sub.10)-- group, a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 or 2 alkyl groups, wherein, in the cycloalkyl part, in each case a methylene group is replaced by an oxygen or sulphur atom or by a sulphinyl, sulphonyl, N-alkyl-N-oxido-imino or R.sub.9 N group, wherein R.sub.9 is as defined above, a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which in each case a methylene group is replaced by a carbonyl group, a C.sub.4-7 -cycloalkylmethyl group which is optionally substituted by 1 or 2 alkyl groups and is additionally substituted in the cycloalkyl part by R.sub.5, wherein R.sub.5 is defined as mentioned above, a cyclopentyl or cyclopentylalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which in each case two hydrogen atoms in the cyclopentyl part are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by a carbon atom, a cyclohexyl, cyclohexylalkyl, cycloheptyl or cycloheptylalkyl group which is optionally substituted by 1 to 4 alkyl groups and in which in each case two hydrogen atoms in the cycloalkyl part are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by a carbon atom, or contains 1 or 2 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by two carbon atoms, a 5-norbornen-2-yl or 5-norbornen-2-yl-alkyl group which is optionally substituted by 1 to 4 alkyl groups, a 3-quinuclidinyl, 4-quinuclidinyl, 3-quinuclidinyl-alkyl, 4-quinuclidinyl-alkyl, azabicyclo›2.2.1!hept-4-yl, azabicyclo›2.2.1!hept-4-yl-alkyl or adamantyl group, or R.sub.10 is a hydrogen atom or an alkyl group and R.sub.11 is a hydroxyl or alkoxy group, their tautomers, their stereoisomers and their salts, wherein, unless mentioned otherwise, the aryl parts mentioned in the definition of the abovementioned radicals are to be understood as meaning a phenyl group, which can in each case be monosubstituted by R.sub.12, mono-, di- or trisubstituted by R.sub.13 or monosubstituted by R.sub.12 and additionally mono- or disubstituted by R.sub.13, wherein the substituents can be identical or different, and R.sub.12 is a cyano, carboxyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkoxycarbonyl, alkylcarbonyl, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, alkylsulphonyloxy, perfluoroalkyl, perfluoroalkoxy, nitro, amino, alkylamino, hydroxy-C.sub.2-4 -alkylamino, N-alkyl-hydroxy-C.sub.2-4 -alkylamino, di(hydroxy-C.sub.2-4 -alkyl)amino, dialkylamino, alkylcarbonylamino, phenylalkylcarbonylamino, phenylcarbonylamino, alkylsulphonylamino, phenylalkylsulphonylamino, phenylsulphonylamino, N-alkyl-alkylcarbonylamino, N-alkyl-phenylalkylcarbonylamino, N-alkyl-phenylcarbonylamino, N-alkyl-alkylsulphonylamino, N-alkyl-phenylalkylsulphonylamino, N-alkyl-phenylsulphonylamino, aminosulphonyl, alkylaminosulphonyl or dialkylaminosulphonyl group, a 5- to 7-membered alkylenimino group which is optionally substituted by 1 to 2 alkyl groups or a hydroxyalkyl group, wherein, in the abovementioned 6- to 7-membered alkylenimino groups, in each case a methylene group in the 4-position can be replaced by an oxygen atom or an R.sub.9 N group, wherein a 5- to 7-membered alkylenimino group which is optionally substituted by i to 2 alkyl groups or a hydroxyalkyl group, wherein in each case one or two methylene groups adjacent to the nitrogen atom are replaced by in each case a carbonyl group, an (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- group, wherein R.sub.6 to R.sub.8 are defined as mentioned above, R.sub.13 is an alkyl, hydroxyl or alkoxy group or a fluorine, chlorine, bromine or iodine atom, wherein two radicals R.sub.13, if these are bonded to adjacent carbon atoms, can also be an alkylene group having 3 to 6 carbon atoms, a 1,3-butadiene-1,4-diylene group or a methylenedioxy group, and, unless mentioned otherwise, the abovementioned alkyl, alkylene and alkoxy parts in each case contain 1 to 4 carbon atoms and, unless mentioned otherwise, each carbon atom in the abovementioned alkylene or cycloalkylene parts which is bonded to a nitrogen, oxygen or sulphur atom cannot be bonded to a further halogen, nitrogen, oxygen or sulphur atom.

4. The pyrimido›5,4-d!pyrimidine according to claim 1 or claim 2, in which R.sub.a is a hydrogen atom or an alkyl group, R.sub.b is a phenyl group which is substituted by the radicals R.sub.1 to R.sub.3, wherein R.sub.1 is a hydrogen, fluorine, chlorine, bromine or iodine atom, an alkyl, hydroxyl, alkoxy, C.sub.3-6 -cycloalkyl or C.sub.5-6 -cycloalkoxy group, an ethoxy group which is substituted in the 2-position by a hydroxyl, alkoxy or phenoxy group, a C.sub.2-5 -alkenyl or C.sub.3-5 -alkenyloxy group, wherein the vinyl part cannot be linked to the oxygen atom, a C.sub.2-5 -alkynyl or C.sub.3-5 -alkynyloxy group, wherein the ethynyl part cannot be linked to the oxygen atom, a phenyl, phenoxy, phenylalkyl, phenylalkoxy, alkoxyalkyl, phenoxyalkyl, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, alkylaminocarbonylalkyl, dialkylaminocarbonylalkyl, cyanoalkyl, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, alkylsulphonyloxy, trifluoromethylsulphenyl, trifluoromethylsulphonyl, nitro, amino, alkylamino, dialkylamino, pyrrolidino, piperidino, morpholino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, trifluoromethylsulphonylamino, N-alkyl-trifluoromethylsulphonylamino, alkylcarbonyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl or cyano group, a methyl or methoxy group which is substituted by 1 to 3 fluorine atoms, an ethyl or ethoxy group which is substituted by 1 to 5 fluorine atoms, R.sub.2 is a hydrogen, fluorine, chlorine or bromine atom or an alkyl, trifluoromethyl, amino, alkylamino, dialkylamino, alkylcarbonylamino, alkylsulphonylamino, trifluoromethylsulphonylamino, hydroxyl or alkoxy group, R.sub.3 is a hydrogen, fluorine, chlorine or bromine atom or an alkyl group, or R.sub.2 together with R.sub.3, if these are bonded to adjacent carbon atoms, is a methylenedioxy or n-C.sub.3-6 -alkylene group or a 1,3-butadiene-1,4-diylene group which is optionally substituted by a fluorine, chlorine or bromine atom or by an alkyl, alkoxy or trifluoromethyl group and R.sub.c is a mercapto, alkylsulphenyl, alkylsulphinyl or alkylsulphonyl group, a hydroxyl, phenoxy or phenyl-C.sub.1-2 -alkoxy group, a C.sub.2-4 -alkoxy group, which is substituted by a hydroxyl, alkoxy, (2-hydroxyethyl)amino, dialkylamino, morpholino, 1-pyrrolidinyl, 1-piperidinyl, 4-methyl-1-piperazinyl, 4-acetyl-1-piperazinyl, 4-methylsulphonyl-1-piperazinyl, 4-methoxycarbonyl-1-piperazinyl, 4-formyl-1-piperazinyl or 4-dimethylaminocarbonyl-1-piperazinyl group, a C.sub.3-4 -alkoxy group, which is substituted by two hydroxyl groups, a C.sub.1-2 -alkoxy group, which is substituted by a C.sub.3-7 -cycloalkyl group which is optionally substituted by one or two methyl groups, wherein, in the abovementioned C.sub.4-6 -cycloalkyl groups, in each case a methylene group can be replaced by an oxygen atom, a C.sub.4-6 -cycloalkoxy group which is optionally substituted by a hydroxyl, dialkylamino, alkoxy, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylcarbonylamino, alkylsulphonylamino or alkoxycarbonylamino group, a cyclopentyloxy group in which the methylene group in the 3-position is replaced by an oxygen atom or by an alkylimino group, a cyclohexyloxy group in which the methylene group in the 3- or or 4-position is replaced by an oxygen atom or by an alkylimino, alkylcarbonyl-imino, alkoxycarbonyl-imino or alkylsulphonyl-imino group, an allyloxy or propargyloxy group which is optionally substituted by one or two methyl groups, a 1-azetidinyl group, a 1-pyrrolidinyl group, which can be substituted by 1 to 2 alkyl groups, by a phenyl, carboxyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, piperazinocarbonyl or 4-alkyl-piperazinocarbonyl group or in the 3-position also by a hydroxyl, alkoxy, amino, alkylamino, dialkylamino, alkylcarbonylamino, alkoxycarbonylamino, formylamino, cyanoamino, alkylsulphonylamino, dialkylaminocarbonylamino, N-alkyl-dialkylaminocarbonylamino, N-alkyl-dialkylaminocarbonylamino or cyano group, a 1-pyrrolidinyl group in which two hydrogen atoms on the carbon skeleton are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by an atom, a 1-piperidinyl group, which can be substituted by 1 to 4 alkyl groups, by a phenyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl, dialkylaminoalkyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, piperazinocarbonyl or 4-alkyl-piperazinocarbonyl group or in the 3- or 4-position also by a hydroxyl, alkoxy, amino, alkylamino, dialkylamino, alkylcarbonylamino, alkoxycarbonylamino, formylamino, cyanoamino, alkyl sulphonylamino, dialkylaminocarbonylamino, N-alkyl-dialkylaminocarbonylamino or cyano group, a 1-piperidinyl group, which is substituted by 1 to 2 alkyl groups or a phenyl group and additionally by a hydroxyl group, a 1-piperidinyl group in which two hydrogen atoms in the 3-position or in the 4-position are replaced by a --O--CH.sub.2 CH.sub.2 --O-- or --O--CH.sub.2 CH.sub.2 CH.sub.2 --O-- group, a 1-piperidinyl group in which two hydrogen atoms on the carbon skeleton are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by an atom, or contains 1 or 2 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by two atoms, a 1-piperidinyl group which is optionally substituted by 1 or 2 alkyl groups and in which the methylene group in the 4-position is replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, imino, alkyl-imino, hydroxy-C.sub.2-4 -alkyl-imino, alkoxy-C.sub.2-4 -alkyl-imino, aminocarbonylalkylimino, alkylaminocarbonylalkyl-imino, dialkylaminocarbonylalkyl-imino, amino-C.sub.2-4 -alkyl-imino, alkylamino-C.sub.2-4 -alkyl-imino, dialkylamino-C.sub.2-4 -alkyl-imino, hydroxy-C.sub.2-4 -alkoxy-C.sub.2-4 -alkyl-imino, phenyl-imino, phenylalkyl-imino, alkylcarbonyl-imino, alkylsulphonyl-imino, phenylcarbonyl-imino, phenylsulphonyl-imino or N-oxido-N-alkyl-imino group, a 1-azacyclohept-1-yl group which is optionally substituted by 1 or 2 alkyl groups and in which in each case the methylene group in the 4-position can be replaced by an oxygen atom or by an imino, N-alkyl-imino, N-phenyl-imino, N-phenylalkyl-imino, N-alkylcarbonyl-imino, N-alkylsulphonyl-imino, N-phenylcarbonyl-imino or N-phenylsulphonyl-imino group or two hydrogen atoms in the 3,6-position can be replaced by a --CH.sub.2 CH.sub.2 -- group, a 2-isoindolinyl, 1,2,3,4-tetrahydro-isoquinolin-2-yl or 2,3,4,5-tetrahydro-1H-3-benzazepin-3-yl group, which can in each case be substituted in the benzo part by a fluorine, chlorine or bromine atom or by an alkyl, trifluoromethyl or alkoxy group, or an (R.sub.10 NR.sub.11)-- group, in which R.sub.10 is a hydrogen atom or a C.sub.1-6 -alkyl group, which can be substituted by a hydroxyl or alkoxy group from position 2, and R.sub.11 is a hydrogen atom, a C.sub.1-8 -alkyl group, which can be substituted by a phenyl, C.sub.3-6 -cycloalkyl, hydroxyl, alkoxy, cyano, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, (2-hydroxyethyl)aminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, 1-piperazinylcarbonyl, 4-alkyl-1-piperazinylcarbonyl, amino, formylamino, alkylamino, dialkylamino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkoxycarbonylamino, N-alkyl-alkoxycarbonyl-amino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, phenylcarbonylamino, N-alkyl-phenylcarbonylamino, phenyl-sulphonylamino, N-alkyl-phenylsulphonylamino, alkylsulphenyl, alkylsulphinyl, alkylsulphonyl, 1-pyrrolidinyl, 2-oxo-1-pyrrolidinyl, 1-piperidinyl, 2-oxo-1-piperidinyl, morpholino, 1-piperazinyl, 4-alkyl-1-piperazinyl, 4-alkylcarbonyl-1-piperazinyl, 4-alkylsulphonyl-1-piperazinyl, 4-alkoxycarbonyl-1-piperazinyl, 4-cyano-1-piperazinyl, 4-formyl-1-piperazinyl, 4-aminocarbonyl-1-piperazinyl, 4-alkylaminocarbonyl-1-piperazinyl or 4-dialkylaminocarbonyl-1-piperazinyl or a (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- group, wherein R.sub.6 and R.sub.7 together are an n-C.sub.2-3 -alkylene bridge and R.sub.8 is a hydrogen atom or an alkyl group, a methyl group which is substituted by a 1,4,7,10-tetraoxacyclododecyl, 1,4,7,10,13-pentaoxacyclopentadecyl or a 1,4,7,10,13,16-hexaoxacyclooctadecyl group, a 2,2,2-trifluoroethyl group, a C.sub.3-5 -alkyl group which is substituted by 2 to 5 hydroxyl groups, a C.sub.3-5 -alkyl group which is substituted by a hydroxyl and additionally by an amino group, a C.sub.2-4 -alkyl group which is substituted by a phenyl group and additionally by a hydroxyl group and which can optionally additionally be substituted by a hydroxyl or alkoxy group, an alkenyl or alkynyl group which has in each case 3 to 6 carbon atoms and is optionally substituted by a phenyl group, wherein the vinyl or ethynyl part cannot be linked to the nitrogen atom, a C.sub.2-4 -alkyl group which is substituted by a C.sub.2-4 -alkoxy group which is substituted in the .omega.-position by a hydroxyl or alkoxy group, a phenyl group, a phenyl group which is substituted by an alkylcarbonylamino, N-alkyl-alkylcarbonylamino, (2-hydroxyethyl)amino, di-(2-hydroxyethyl)amino, N-alkyl-(2-hydroxyethyl)amino, alkylamino or dialkylamino group or by an (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- group wherein R.sub.6 to R.sub.8 are defined as mentioned above, a phenyl group, which is substituted by a pyrrolidino, piperidino, 2-oxo-pyrrolidino, 2-oxo-piperidino, morpholino, 1-piperazinyl or 4-alkyl-1-piperazinyl group, wherein the abovementioned heterocyclic parts can be substituted on the carbon skeleton in each case by 1 or 2 alkyl groups or by a hydroxyalkyl group, a C.sub.3-7 -cycloalkyl group which can be substituted by 1 or 2 alkyl groups or by a phenyl, carboxyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, piperazinocarbonyl or 4-alkyl-piperazinocarbonyl group, a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 or 2 methyl groups and is substituted by a hydroxymethyl, cyano, hydroxyl, alkoxy, amino, alkylamino, dialkylamino, 2-hydroxyethylamino, di-(2-hydroxyethyl)amino, N-alkyl-2-hydroxy-ethylamino, N,N-dialkyl-N-oxido-amino, alkoxycarbonylamino, N-alkyl-alkoxycarbonylamino, alkylcarbonylamino, N-alkyl-alkylcarbonylamino, alkylsulphonylamino, N-alkyl-alkylsulphonylamino, phenylcarbonylamino, N-alkyl-phenylcarbonyl-amino, phenylsulphonylamino, N-alkylphenylsulphonylamino or by an (R.sub.8 NR.sub.7)--CO--NR.sub.6 -- group, wherein R.sub.6 to R.sub.8 are defined as mentioned above, a C.sub.5-7 -cycloalkyl group which is optionally substituted by 1 or 2 methyl groups and is substituted by a pyrrolidino, piperidino, 2-oxo-pyrrolidino, 2-oxo-piperidino, morpholino, 1-piperazinyl, 4-alkyl-1-piperazinyl or 4-alkylcarbonyl-1-piperazinyl group, wherein the abovementioned heterocyclic parts can in each case be substituted on the carbon skeleton by 1 or 2 alkyl groups or by a hydroxymethyl group, a C.sub.5-7 -cycloalkenyl group which is optionally substituted by 1 or 2 alkyl groups, wherein the vinyl part cannot be bonded to the nitrogen atom of the (R.sub.11 NR.sub.10)-- group, a tetrahydrofurfuryl group, a cyclopentyl group in which the methylene group in the 3-position is replaced by an oxygen atom or an imino, alkylimino, alkylcarbonylimino, formylimino, aminocarbonylimino, alkylaminocarbonylimino, alkoxycarbonylimino, alkylsulphonylimino, dialkylaminocarbonylimino or cyanoimino group, a cyclohexyl group in which the methylene group in the 3-position is replaced by an imino, alkyl-imino, alkylcarbonyl-imino, alkoxycarbonyl-imino or alkylsulphonyl-imino group, a cyclohexyl group in which the methylene group in the 4-position is replaced by an oxygen atom or an imino, N-alkyl-imino, N-phenyl-imino, N-phenylalkyl-imino, N-formyl-imino, N-alkylcarbonyl-imino, N-phenylcarbonyl-imino, N-alkoxycarbonyl-imino, N-cyano-imino, N-aminocarbonyl-imino, N-alkylamino-carbonyl-imino, N,N-dialkylaminocarbonyl-imino, N-alkyl-N-oxido-imino, N-alkylsulphonyl-imino or N-phenylsulphonylimino group, a cyclohexyl group in which a methylene group is replaced by a carbonyl group, a cyclopentyl or cyclohexyl group which is optionally substituted by 1 to 2 methyl groups and is substituted by a carboxyalkoxy, alkoxycarbonylalkoxy, aminocarbonylalkoxy, alkylaminocarbonylalkoxy, dialkylaminocarbonylalkoxy, pyrrolidinocarbonylalkoxy, piperidinocarbonylalkoxy, morpholino-carbonylalkoxy, carboxyalkyl, alkoxycarbonylalkyl, aminocarbonylalkyl, alkylaminocarbonylalkyl, dialkylaminocarbonylalkyl, pyrrolidinocarbonylalkyl, piperidinocarbonylalkyl or morpholinocarbonylalkyl group, a cyclohexylmethyl group, wherein the cyclohexyl part is substituted by a carboxyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl, morpholinocarbonyl, alkoxycarbonyl or hydroxymethyl group, a cyclohexyl or cyclohexylmethyl group which is option-ally substituted by 1 to 3 methyl groups and in which in each case two hydrogen atoms in the cyclohexyl part are replaced by a straight-chain alkylene bridge, wherein this bridge contains 4 or 5 carbon atoms if the two hydrogen atoms are on the same carbon atom, or contains 3 or 4 carbon atoms if the two hydrogen atoms are on adjacent carbon atoms, or contains 2 or 3 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by a carbon atom, or contains 1 or 2 carbon atoms if the two hydrogen atoms are on carbon atoms which are separated by two carbon atoms, a 5-norbornen-2-yl or 5-norbornen-2-yl-methyl group which is optionally substituted by i to 3 methyl groups, a 3-quinuclidinyl, 4-quinuclidinyl or adamantyl group, or R.sub.10 is a hydrogen atom or an alkyl group and R.sub.11 is a hydroxyl or alkoxy group, their tautomers, their stereoisomers and their salts, wherein the abovementioned phenyl radicals in each case can be substituted by a fluorine, chlorine or bromine atom or by a nitro, alkyl, alkoxy, trifluoromethyl or hydroxyl group and, unless mentioned otherwise, the abovementioned alkyl, alkylene and alkoxy parts in each case contain 1 to 4 carbon atoms and, unless mentioned otherwise, each carbon atom in the abovementioned alkylene or cycloalkylene parts which is bonded to a nitrogen, oxygen or sulphur atom cannot be bonded to a further halogen, nitrogen, oxygen or sulphur atom.

5. The pyrimido›5,4-d!pyrimidine according to claim 1 or claim 2, in which R.sub.a is a hydrogen atom or a methyl group, R.sub.b is a 2-naphthyl, 1,2,3,4-tetrahydro-6-naphthyl or 5-indanyl group, or a phenyl group which is substituted by the radicals R.sub.1 to R.sub.3, wherein R.sub.1 is a hydrogen, fluorine, chlorine, bromine or iodine atom, a C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, C.sub.3-6 -cycloalkyl, C.sub.5-6 -cycloalkoxy, cyano, methoxycarbonyl, ethoxycarbonyl, ethynyl or nitro group, a methyl or methoxy group which is substituted by 1 to 3 fluorine atoms, an ethyl or ethoxy group which is substituted by 1 to 5 fluorine atoms, R.sub.2 is a hydrogen, fluorine or chlorine atom or a methyl, hydroxyl, methoxy, amino, C.sub.1-2 -alkylamino, di-C.sub.1-2 -alkylamino, C.sub.1-2 -alkylcarbonylamino, C.sub.1-2 -alkylsulphonylamino, trifluoromethylsulphonylamino or trifluoromethyl group, R.sub.3 is a hydrogen, fluorine, chlorine or bromine atom or a methyl group and R.sub.c is a methylsulphinyl or methylsulphonyl group, a hydroxyl group, an ethoxy group which is substituted in the 2-position by a hydroxyl, methoxy, morpholino or (2-hydroxyethyl)amino group, a 2-propyloxy group which is substituted in the 1-position by a methoxy or dimethylamino group, a methoxy group which is substituted by a 2-tetrahydrofuryl, 2-tetrahydropyranyl or 3-methyl-3-oxetanyl group, a cyclobutyloxy group, a cyclopentyloxy group which is optionally substituted in the 3-position by a hydroxyl group, a cyclopentyloxy group in which the methylene group in the 3-position is replaced by an oxygen atom or by a methyl-imino group, a cyclohexyloxy group which can be substituted in the 2-, 3-or 4-position by a hydroxyl group or in the 4-position also by a di-(C.sub.1-2 -alkyl)amino, methoxy, carboxyl, methoxycarbonyl, dimethylaminocarbonyl, methylaminocarbonyl, aminocarbonyl, acetylamino, methylsulphonylamino, methoxycarbonylamino or tert-butyloxycarbonylamino group, a cyclohexyloxy group in which the methylene group in the 3-position is replaced by a methyl-imino group or the methylene group in the 4-position is replaced by an oxygen atom or by a methyl-imino, acetyl-imino, tert-butyloxycarbonyl-imino, methoxycarbonyl-imino or methylsulphonyl-imino group, an allyloxy group, a 1-azetidinyl group, a 1-pyrrolidinyl group which can be substituted by 1 or 2 methyl groups, by a carboxyl, methoxycarbonyl, ethoxycarbonyl, aminocarbonyl, C.sub.1-2 -alkylaminocarbonyl, or di-(C.sub.1-2)-alkylamino-carbonyl group or in the 3-position by an amino, C.sub.1-2 -alkylamino, di-(C.sub.1-2 -alkyl)amino, C.sub.1-2 -alkoxycarbonylamino, C.sub.1-2 -alkylcarbonylamino, C.sub.1-2 -alkylsulphonylamino, cyanoamino, formylamino or dimethylaminocarbonylamino group, a 1-pyrrolidinyl group in which two hydrogen atoms in the 3-position are replaced by an n-C.sub.4-5 -alkylene bridge, a 1-piperidinyl group which can be substituted by 1 to 4 methyl groups, by a phenyl, hydroxy-C.sub.1-2 -alkyl, carboxyl, C.sub.1-2 -alkoxycarbonyl, aminocarbonyl, C.sub.1-2 -alkylaminocarbonyl, di-(C.sub.1-2)-alkylaminocarbonyl, pyrrolidinocarbonyl or morpholinocarbonyl group or in the 3- or 4-position by a hydroxyl, C.sub.1-2 -alkoxy, amino, C.sub.1-2 -alkylamino, di-(C.sub.1-2) -alkylamino, C.sub.1-2 -alkylcarbonylamino, C.sub.1-2 -alkoxycarbonylamino, formylamino, cyanoamino, di-(C.sub.1-2 -alkyl)aminocarbonylamino, C.sub.1-2 -alkylsulphonylamino or cyano group, a 1-piperidinyl group in which two hydrogen atoms in the 3-position or in the 4-position are replaced by an n-C.sub.4-5 -alkylene bridge or by an --O--CH.sub.2 CH.sub.2 --O-- bridge, a 1-piperidinyl group which is substituted by 1 or 2 methyl groups or a phenyl group and additionally in the 3- or 4-position by a hydroxyl group, a 1-piperidinyl group in which two hydrogen atoms in the 2,5-position are replaced by a --CH.sub.2 -- or --CH.sub.2 CH.sub.2 -- bridge, a 1-piperidinyl group which is optionally substituted by 1 to 2 methyl groups and in which the methylene group in the 4-position is replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, imino, C.sub.1-2 -alkyl-imino, (2-hydroxyethyl)-imino, 2-(2-hydroxyethoxy)ethyl-imino, (2-aminoethyl)-imino, C.sub.1-3 -alkylaminocarbonylmethyl-imino, N-oxido-N-C.sub.1-2 -alkylamino, phenyl-imino, benzyl-imino, acetylimino or methanesulphonyl-imino group, a 1-azacyclohept-1-yl group in which two hydrogen atoms in the 3,6-position can be replaced by a --CH.sub.2 CH.sub.2 -- group, a 1,2,3,4-tetrahydro-isoquinolin-2-yl or 2,3,4,5-tetrahydro-1H-3-benzazepin-3-yl group or an (R.sub.10 NR.sub.11)-- group in which R.sub.10 is a hydrogen atom, a C.sub.1-4 -alkyl group or 2-hydroxyethyl group and R.sub.11 is a hydrogen atom, a C.sub.1-6 -alkyl, C.sub.3-6 -cycloalkyl-methyl or phenyl-C.sub.1-3 -alkyl group, a C.sub.3-6 -cycloalkyl, allyl or propargyl group which is optionally substituted by 1 or 2 methyl groups, a phenyl group which can be substituted by a hydroxyl or methyl group or in the 4-position by an N-C.sub.1-2 -alkyl-C.sub.1-2 -alkylcarbonyl-amino, N-C.sub.1-2 -alkyl-(2-hydroxyethyl)amino, di-(2-hydroxyethyl)amino, 1-pyrrolidinyl, 2-oxo-1-pyrrolidinyl, 2-hydroxymethyl-1-pyrrolidinyl, 2-oxo-1-imidazolidinyl, 3-methyl-2-oxo-1-imidazolidinyl or morpholino group, a methyl group which is substituted by a carboxyl, C.sub.1-2 -alkoxycarbonyl, aminocarbonyl, C.sub.1-2 -alkylaminocarbonyl, di-C.sub.1-2 -alkylaminocarbonyl, pyrrolidinocarbonyl, piperidinocarbonyl or morpholinocarbonyl group, an ethyl group which is optionally substituted by a methyl group and is substituted in the 2-position by a hydroxyl, C.sub.1-2 -alkoxy, amino, C.sub.1-2 -alkylamino, di-C.sub.1-2 -alkylamino, acetylamino, 1-pyrrolidinyl, morpholino, 1-piperazinyl, 4-methyl-1-piperazinyl, 4-acetyl-1-piperazinyl, 4-aminocarbonyl-1-piperazinyl, 4-dimethylaminocarbonyl-1-piperazinyl, 4-methylaminocarbonyl-1-piperazinyl, 4-methylsulphonyl-1-piperazinyl, 4-methoxycarbonyl-1-piperazinyl or 4-cyano-1-piperazinyl group, a 2-hydroxyethyl group which is substituted in the ethyl part by a phenyl, 3-hydroxyphenyl, 4-hydroxyphenyl, 4-nitrophenyl or benzyl group, wherein the ethyl part of the abovementioned groups can additionally be substituted by a methyl, hydroxymethyl or methoxymethyl group, a methyl group which is substituted by a 1,4,7,10-tetraoxacyclododecyl, 1,4,7,10,13-pentaoxacyclopentadecyl or a 1,4,7,10,13,16-hexaoxacyclooctadecyl group, a 2,2,2-trifluoroethyl group, a propyl group which is substituted in the 3-position by a hydroxyl, cyano, carboxyl, aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, formylamino, methoxycarbonylamino, morpholino or 2-oxo-1-pyrrolidinyl group, a butyl group which is substituted in the 4-position by a hydroxyl group, a 3-butyl group which is substituted in the 1-position by a hydroxyl group and additionally in the 3-position by a methyl group, a 2-butyl group which is substituted in the 1-position by a hydroxyl group and additionally in the 3-position by a methyl group. a 4-pentyl group which is substituted in the 1-position by a hydroxyl group and additionally in the 4-position by a methyl group, a 2,3-dihydroxypropyl,3-amino-2-hydroxypropyl, tris-(3-hydroxypropyl)methyl, 1,3-dihydroxy-2-propyl, 1,3-dihydroxy-2-methyl-2-propyl or tris-(hydroxymethyl)methyl group, a 2-propyl group which is substituted in the 2-position by a hydroxylmethyl, C.sub.1-2 -alkoxymethyl, carboxyl, C.sub.1-2 -alkoxycarbonyl, aminocarbonyl, N-C.sub.1-2 -alkylaminocarbonyl, N,N-di-C.sub.1-2 -alkylaminocarbonyl, pyrrolidinocarbonyl, morpholinocarbonyl or (2-hydroxyethyl)aminocarbonyl group, a 4-tetrahydropyranyl, tetrahydrofurfuryl, 1-deoxy-1-D-sorbityl or 2-(2-hydroxyethyloxy)ethyl group, a cyclopentyl group which is substituted in the 2- or 3-position by a hydroxyl group or in the 1-position by a hydroxymethyl group, a cyclohexyl group which is substituted in the 2-, 3- or 4-position by a hydroxymethyl, hydroxyl, C.sub.1-2 -alkoxy, (C.sub.1-4 -alkoxy)-carbonylamino, amino, C.sub.1-2 -alkylamino, di-C.sub.1-2 -alkylamino, carboxyl, C.sub.1-2 -alkoxycarbonyl, aminocarbonyl, C.sub.1-2 -alkylaminocarbonyl, di-C.sub.1-2 -alkylaminocarbonyl, N-oxido-di-C.sub.1-2 -alkylamino, pyrrolidinocarbonyl, morpholinocarbonyl, C.sub.1-2 -alkylcarbonyl-amino or C.sub.1-2 -alkylsulphonylamino group and can additionally be substituted by a methyl group, a cyclohexyl group which is substituted in the 4-position by a 1-pyrrolidinyl, 2-oxo-1-pyrrolidinyl, 2-hydroxymethyl-1-pyrrolidinyl, N-C.sub.1-2 -alkyl-(2-hydroxyethyl)amino, di-(2-hydroxyethyl)amino, N-C.sub.1-2 -alkyl-C.sub.1-2 -alkylcarbonylamino, morpholino, 2-oxo-1-imidazolidinyl, 3-methyl-2-oxo-1-imidazolidinyl, carboxy-C.sub.1-2 -alkyl, carboxy-C.sub.1-2 -alkoxy, C.sub.1-2 -alkoxycarbonyl, C.sub.1-2 -alkyl, C.sub.1-2 -alkoxycarbonyl-C.sub.1-2 -alkoxy, aminocarbonyl-C.sub.1-2 -alkyl, aminocarbonyl-C.sub.1-2 -alkoxy, C.sub.1-2 -alkylamino-carbonyl-C.sub.1-2 -alkyl, C.sub.1-2 -alkylamino-carbonyl-C.sub.1-2 -alkoxy, di-C.sub.1-2 -alkylamino-carbonyl-C.sub.1-2 -alkyl, di-C.sub.1-2 -alkylamino-carbonyl-C.sub.1-2 -alkoxy, pyrrolidinocarbonyl-C.sub.1-2 -alkyl, pyrrolidinocarbonyl-C.sub.1-2 -alkoxy, morpholinocarbonyl-C.sub.1-2 -alkyl, morpholinocarbonyl-C.sub.1-2 -alkoxy, piperidinocarbonyl-C.sub.1-2 -alkyl or piperidinocarbonyl-C.sub.1-2 -alkoxy group, a cyclohexyl group in which two hydrogen atoms in the 4-position are replaced by an oxo group or an n-C.sub.4-5 -alkylene bridge, a cyclohexyl group in which the methylene group in the 4-position is replaced by an imino, C.sub.1-2 -alkyl-imino, phenyl-C.sub.1-2 -alkyl-imino, N-methyl-N-oxido-imino, formyl-imino, C.sub.1-2 -alkylcarbonyl-imino, C.sub.1-2 -alkylsulphonyl-imino, C.sub.1-2 -alkoxycarbonyl-imino, cyano-imino, aminocarbonyl-imino, C.sub.1-2 -alkylaminocarbonyl-imino or N,N-di-C.sub.1-2 -alkylaminocarbonylimino group, a cyclohexyl group in which the methylene group in the 3-position is replaced by an imino, C.sub.1-2 -alkyl-imino, C.sub.1-2 -alkylcarbonyl-imino, C.sub.1-2 -alkylsulphonyl-imino or C.sub.1-2 -alkoxycarbonyl-imino group, a cyclopentyl group in which the methylene group in the 3-position is replaced by an oxygen atom or an imino, C.sub.1-2 -alkyl-imino, formyl-imino, C.sub.1-2 -alkylcarbonyl-imino, C.sub.1-2 -alkylsulphonyl-imino, C.sub.1-2 -alkoxycarbonyl-imino, cyano-imino or N,N-di-C.sub.1-2 -alkylaminocarbonylimino group, a cyclohexylmethyl group, wherein the cyclohexyl part is substituted in the 4-position by a carboxyl, C.sub.1-2 -alkoxycarbonyl, N,N-di-C.sub.1-2 -alkylaminocarbonyl or morpholinocarbonyl group, a norbornan-2-yl, norbornan-2-yl-methyl, 5-norbornen-2-yl-methyl, bornyl, 3-quinuclidinyl or adamantyl group or R.sub.10 is a hydrogen atom or a methyl group and R.sub.11 is a hydroxyl or methoxy group, their tautomers, their stereoisomers and their salts.

6. Pyrimido›5,4-d!pyrimidine I according to claim 1 or claim 2, in which R.sub.a is a hydrogen atom or a methyl group, R.sub.b is a 2-naphthyl or 5-indanyl group or a phenyl group which is substituted by the radicals R.sub.1 to R.sub.3, wherein R.sub.1 is a hydrogen, fluorine, chlorine, bromine or iodine atom or a methyl, ethyl, tert-butyl, trifluoromethyl, ethynyl, methoxy, cyclopropyl, trifluoromethoxy, cyano, ethoxycarbonyl or nitro group, R.sub.2 is a hydrogen, fluorine or chlorine atom or an amino, methyl or trifluoromethyl group and R.sub.3 is a hydrogen, chlorine or bromine atom, and R.sub.c is a hydroxyl, cyclopentyloxy, 2-›(2-hydroxyethyl)amino!-ethoxy, methylsulphinyl or methylsulphonyl group, a 1-azetidinyl group or a 1-pyrrolidinyl group which is optionally substituted by one or two methyl groups, a 1-piperidinyl group which is substituted by a hydroxymethyl group, a 1-piperidinyl group which is optionally substituted by one or two methyl groups and in which the methylene group in the 4-position can be replaced by an oxygen or sulphur atom or by a carbonyl, sulphinyl, sulphonyl, imino, methyl-imino, N-oxido-N-methyl-imino, 2-propylaminocarbonyl-methyl-imino, phenyl-imino, benzyl-imino, acetyl-imino or methylsulphonyl-imino group, a 1-piperidinyl group which is substituted in the 3-position by a hydroxyl or diethylaminocarbonyl group or in the 4-position by a hydroxyl, carboxyl, methoxycarbonyl, aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, pyrrolidinocarbonyl, morpholinocarbonyl, amino, acetylamino, methoxycarbonylamino, formylamino, cyanoamino, dimethylaminocarbonylamino, methylsulphonylamino or phenyl group, a 4-hydroxy-4-phenyl-1-piperidinyl group, a 1,2,3,4-tetrahydro-isoquinolin-2-yl or 2,3,4,5-tetrahydro-1H-3-benzazepin-3-yl group, a 1-piperidinyl group in which two hydrogen atoms in the 4-position are replaced by an --OCH.sub.2 CH.sub.2 --O-- bridge, a 1-azacyclohept-1-yl group in which two hydrogen atoms in the 3- and 6-position are replaced by a --CH.sub.2 --CH.sub.2 -- group or an (R.sub.10 NR.sub.11)-- group, in which R.sub.10 is a hydrogen atom, a C.sub.1-4 -alkyl group or a 2-hydroxyethyl group and R.sub.11 is a hydrogen atom, a phenyl group which is optionally substituted by a methyl group, a phenyl group which is substituted in the 4-position by a morpholino or 2-(hydroxymethyl)-1-pyrrolidinyl group, a C.sub.1-6 -alkyl, C.sub.3-6 -cycloalkyl, phenyl-C.sub.1-3 -alkyl, cyclopropylmethyl, allyl, propargyl, 2-hydroxyethyl, 1-hydroxy-2-propyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-methyoxyethyl, 1-adamantyl, norbornan-2-yl, aminocarbonylmethyl, 2-(dimethylamino)ethyl, 3-quinuclidinyl, 2,2,2-trifluoroethyl, 4-piperidinyl, 1-methyl-4-piperidinyl, 1-methyl-1-oxido-4-piperidinyl, 1-ethoxycarbonyl-4-piperidinyl, 1-benzyl-4-piperidinyl, 2-(2-hydroxyethoxy)ethyl, 4-tetrahydropyranyl, 1-hydroxy-2-methyl-2-propyl, 1-methoxy-2-methyl-2-propyl, 2-(methylaminocarbonyl)-2-propyl, 2,3-dihydroxy-1-propyl, 2-(morpholino)ethyl, 1-deoxy-1-D-sorbityl, 3-(2-oxo-1-pyrrolidinyl)-propyl, tris-(hydroxymethyl)methyl, 1,3-dihydroxy-2-propyl, 1,3-dihydroxy-2-methyl-2-propyl or bornyl group, a 2-hydroxyethyl group which is substituted in the 2-position by a phenyl group and in the 1-position additionally by a methyl or hydroxymethyl group, a methylcyclohexyl, 4-carboxy-cyclohexyl, 4-methoxycarbonylcyclohexyl, 4-dimethylaminocarbonyl-cyclohexyl, 4-(1-pyrrolidinylcarbonyl)-cyclohexyl, 4-(morpholinocarbonyl)cyclohexyl, 4-›2-(methoxycarbonyl)ethyl!cyclohexyl, 4-(2-carboxy-ethyl)cyclohexyl, 4-(tert -butyloxycarbonylamino)cyclohexyl, 4-methoxycyclohexyl, 4-aminocyclohexyl, 4-(dimethylamino)cyclohexyl, 4-(N,N-dimethyl-N-oxido-amino)cyclohexyl, 4-(acetylamino)-cyclohexyl, 4-(methylsulphonylamino)-cyclohexyl, 2-hydroxycyclohexyl, 4-hydroxycyclohexyl, 4-(hydroxymethyl)-cyclohexyl, 4-hydroxy-4-methyl-cyclohexyl or 4-oxocyclohexyl group, a methyl group which is substituted by a 1,4,7,10,13-pentaoxacyclopentadecyl or a 1,4,7,10,13,16-hexaoxacyclooctadecyl group, or R.sub.10 is a methyl group and R.sub.11 is a methoxy group, their tautomers, their stereoisomers and their salts.

7. The pyrimido›5,4-d!-pyrimidine according to claim 1 or claim 2: (1) 4-›(3,4-Dichlorophenyl)amino!-6-›(trans-4-hydroxycyclohexyl)-amino!-pyrimi do-›5,4-d!-pyrimidine, (2) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›(trans-4-hydroxycyclohexyl)-amino!- pyrimido-›5,4-d!-pyrimidine, (3) 4-›(3-Bromophenyl)amino!-6-›(trans-4-hydroxycyclohexyl)-amino!-pyrimido-›5 ,4-d!-pyrimidine, (4) 4-›(3-Chlorophenyl)amino!-6-(cyclopropylamino)-pyrimido-›5,4-d!-pyrimidine (5) 4-›(3-Methylphenyl)amino!-6-(4-amino-1-piperidinyl)-pyrimido-›5,4-d!-pyrim idine, (6) 4-›(3-Methylphenyl)amino!-6-›(trans-4-aminocyclohexyl)-amino!-pyrimido›5,4 -d!-pyrimidine, (7) 4-›(3-Methylphenyl)amino!-6-(N-(trans-4-hydroxycyclohexyl)-N-methylamino)- pyrimido-›5,4-d!-pyrimidine, (8) 4-›(3-Methylphenyl)amino!-6-(4-methoxycarbonylamino-1-piperidinyl)-pyrimid o-›5,4-d!-pyrimidine, (9) 4-›(3-Methylphenyl)amino!-6-›trans-4-(morpholinocarbonyl)-cyclohexylamino! -pyrimido-›5,4-d!-pyrimidine, (10) 4-›(3-Methylphenyl)amino!-6-›trans-4-(pyrrolidinocarbonyl)cyclohexylamino! -pyrimido-›5,4-d!-pyrimidine, (11) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›N-(trans-4-hydroxycyclohexyl)-N-met hyl-amino!-pyrimido-›5,4-d!-pyrimidine, (12) 4-›(4-Amino-3,5-dichloro-phenyl)amino!-6-›(triamino!-pyrimidcyclohexyl)-am ino!-pyrimido-›5,4-d!-pyrimidine, (13) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›2-(morpholino)-ethylamino!-pyrimido -›5,4-d!-pyrimidine, (14) 4-›(4-Amino-3,5-dibromo-phenyl)amino!-6-›(trans4-hydroxycyclohexyl)-amino! -pyrimido-›5,4-d!-pyrimidine, (15) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-morpholino-pyrimido-›5,4-d!-pyrimidi ne, (16) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-(1-hydroxy-2-methyl-2-propylamino)-p yrimido-›-d!-pyrimidine, (17) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-(1-hydroxy-2-propylamino)-pyrimido-› 5,4-d!-pyrimidine, (18) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-(1,3-dihydroxy-2-propylamino)-pyrimi do-›5,4-d!-pyrimidine, (19) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›4-amino-1-piperidinyl!-pyrimido-›5, 4-d!-pyrimidine, (20) 4-›(3-Methylphenyl)amino!-6-(4-piperidinyl-amino)-pyrimido-›5,4-d!-pyrimid ine, (21) 4-›(3-Methylphenyl)amino!-6-(4-formylamino-1-piperidinyl)-pyrimido-›5,4-d! -pyrimidine, (22) 4-›(3-Methylphenyl)amino!-6-›(1-ethoxycarbonyl-4-piperidinyl)amino!-pyrimi do-›5,4-d!-pyrimidine, (23) 4-›(3-Methylphenyl)amino!-6-›(3-quinuclidinyl)amino!-pyrimido-›5,4-d!-pyri midine, (24) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›(4-aminocyclohexyl)amino!-pyrimido- ›5,4-d!-pyrimidine, (25) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-(4-piperidinyl-amino)-pyrimido-›5,4- d!-pyrimidine, (26) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›trans-4-(morpholinocarbonyl)cyclohe xylamino!-pyrimido-›5,4-d!-pyrimidine, (27) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›trans-4-(pyrrolidinocarbonyl)cycloh exylamino!-pyrimido-›5,4-d!-pyrimidine, (28) 4-›(4-Fluorophenyl)amino!-6-(cyclopropylamino)-pyrimido-›5,4-d!-pyrimidine (29) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-(cyclopropylamino)-pyrimido-›5,4-d!- pyrimidine, (30) 4-›(3,4-Dichlorophenyl)amino!-6-(cyclopropylamino)-pyrimido-›5,4-d!-pyrimi dine, (31) 1-›(3-Chloro-4-fluoro-phenyl)amino!-6-(1-methyl-4-piperidinyl-amino)-pyrim ido-›5,4-d!-pyrimidine, or (32) 4-›(3-Chloro-4-fluoro-phenyl)amino!-6-›1-trans-4-(dimethylaminocyclohexyl) amino!-pyrimido-›5,4-d!-pyrimidine, or a pharmaceutically acceptable salt thereof.

8. A pharmaceutical composition of matter comprising a pyrimido›5,4-d!pyrimidine according to claim 1 or claim 2 and a pharmaceutically acceptable carrier or diluent.

9. A method of treating disease in a warm-blooded animal by inhibition of signal transduction mediated by tyrosine kinases which comprises administering to the animal a therapeutically effective amount of a pyrimido›5,4-d!pyrimidine according to claim 1 or claim 2.

10. The pyrimido›5,4-d!-pyrimidine according to claim 1 or 2 which is: 4-›(3-chloro-4-fluorophenyl)amino!-6-(1-methyl-4-piperidinyl-amino)-pyrimi do›5,4-d!pyrimidine.

11. The pyrimido›5,4-d!-pyrimidine according to claim 1 or 2 which is: 4-›(3-chloro-4-fluorophenyl)amino!-6-›1-(trans-4-dimethylaminocyclohexyl)a mino!-pyrimido›5,4-d!pyrimidine.