PYRIMIDOPYRIMIDINE COMPOUNDS

Abstract: A range of dipyridamole analogues useful for inhibiting transport of nucleosides or purines across cell membranes, thereby to potentiate the activity of various cytotoxic antitumour drugs, is diclosed. These analogues comprise compounds having general structural formula (I) or pharmaceutically acceptable salts thereof; wherein R1 is chloro and R3 is diethanolamino, or R1 and R3 are identical and are selected from allyl, halo, diethanolamino, solketalo and a group having the formula: -O-Rz or -NHRz, Rz being selected from alkyl, hydroxyalkyl, alkoxyalkyl, dialkoxyalkyl and 2-oxo-alkyl wherein the or each alkyl and/or alkoxy moiety has less than six carbon atoms, and R2 and R4 are identical and are selected from piperidino, N-tetrahydroisoquinolyl, and a benzylamino group having structural formula (II) wherein R5 is H, or an optionally substituted alkyl or benzyl group, and R6 and R7 represent H or optional substituents in the aromatic nucleus selected from halo, alkyl, alkoxy, hydroxy, trifluoromethyl, azido, cyano, nitro, carboxyl, carboxylic ester, amino or a substituted amino NRxRy where Rx and Ry each represent hydrogen or alkyl, subject to the provisos that (a) if R1 and R3 are both chloro or diethanolamino, R2 and R4 are not both benzylamino, i.e. R2 and R4 do not correspond to structure II with R5, R6 and R7 each being hydrogen, and (b) if R2 and R4 are both piperidino, R1 and R3 are not both chloro, diethanolamino, solketalo or (2,3-dimethoxy)propoxy.

Description: PYRIMIDOPYRIMIDINE COMPOUNDS FIELD OF THE INVENTION The present invention relates to dipyridamole analogues that are of interest as being potentially useful chemotherapeutic agents, especially insofar as they possess an ability to inhibit or modulate the transport of certain purine compounds and nucleosides across cell membranes of at least some cell types and are able thereby to enhance or potentiate the activity of certain cytotoxic drugs. BACKGROUND The compound 2 , 6-bis (diethanolamino) - , 8-dipiperi- dinopyrimidopyrimidine, known as dipyridamole and referred to as such in the present specification, and some particular close analogues thereof have been known for some considerable time as effective vasodilator and thrombolytic agents, as disclosed for example in patent documents GB799177 and GB807826 which also describe various methods of synthesis of such compounds. Although the pharmacological activity of dipyridamole is diverse, in at least most cases it is believed to arise as a result of its ability to inhibit or modulate the transport of nucleosides across cell membranes, this nucleoside transport being a major factor which is often implicated in the development of antitumor drug resistance. Not only can dipyridamole directly modulate the activity of cytotoxic compounds which are themselves nucleosides, e.g. cytarabine, fluordeoxyuridine and deoxycoformycin, or which are bases that become converted within the cell into nucleosides, e.g. fluorouracil, but dipyridamole can also indirectly modulate the activity of antimetabolites whose cytotoxicity is influenced by levels of normal nucleosides (e.g. methotrexate, the thy idylate synthase inhibitor CB3717, acivicin and PALA) . In addition it is also known that dipyridamole can act to increase in vi tro cytotoxicity of drugs such as doxrubicin, vinblastme and etoposide. The mechanism of action in the case of the latter cytotoxic compounds appears to involve the induction of higher mtracellular drug levels, and it is believed that this may be caused, m part, by dipyridamole inhibiting drug efflux. These properties of dipyridamole have led to proposals for using it in therapy, especially antitumor therapy, in combination with a range of cytotoxic drugs so as to enhance or potentiate the cytotoxicity of the latter. However, although a high level of activity in enhancing or potentiating the cytotoxicity of such drugs has been demonstrated m some cases m the course of in vi tro experiments, clinical testing and use of dipyridamole in this manner, i.e. in combination with cytotoxic drugs, has been severely handicapped by a problem of low solubility and difficulty in satisfactory formulation for effective administration, together with a major problem arising from the fact that dipyridamole has a strong binding affinity to a plasma protein, α-1 acid glycoprotein (AGP) . This AGP protein is often present at elevated levels in cancer patients, and the effect of the strong AGP binding affinity of dipyridamole is to reduce the plasma or serum concentration of free dipyridamole. This in turn then reduces the ability of the dipyridamole to potentiate the activity of the drugs concerned since it seems that only free dipyridamole is able to modulate or inhibit the membrane transport of nucleosides and cytotoxic drugs . DISCLOSURE OF THE INVENTION One object of the present invention is accordingly to provide pyπmidopyrimidme compounds which can be regarded as being analogues or derivatives of dipyridamole and which, as compared with dipyridamole itself, have a reduced tendency to bind to AGP without any serious loss in ability to modulate or inhibit nucleoside transport across membranes of at least some cell types. A further object is to provide dipyridamole analogues or derivatives for therapeutic use which have a greater solubility m aqueous media, particularly at physiological pH, than dipyridamole itself. It is also an object of the invention to provide a greater range of dipyridamole analogues or derivatives, which may constitute new chemical entities and/or new therapeutic agents, for increasing the choice available of potentially useful alternatives to dipyridamole itself for administering to patients m conjunction with certain cytotoxic drugs in order to potentiate the cytotoxic e fectiveness of the latter. A yet further object is to provide novel compounds that may be useful as intermediates in the preparation of bioactive dipyridamole analogues or derivatives as specified above for use as therapeutic agents. Although many dipyridamole analogues or derivatives investigated are not necessarily significantly better than dipyridamole itself in respect of the properties that give rise to the problems mentioned above, certain analogue compounds have now been identified that it is believed will provide useful and viable alternatives to dipyridamole for use as therapeutic agents m chemotherapy. Moreover there are some compounds which not only exhibit a high degree of nucleoside transport inhibiting activity, comparable with or even stronger than dipyridamole itself, but which surprisingly also have a much reduced binding affinity for AGP as compared to dipyridamole whereby significant nucleoside transport inhibiting activity is retained in the presence of AGP, at least m respect of certain cell types. These compounds are accordingly of particular interest as therapeutic agents for use in medicine, especially when administered m conjunction with certain cytotoxic drugs, e.g. antitumor drugs, for increasing the cytotoxic effectiveness of the latter as previously mentioned. The desirability of developing or identifying further dipyridamole analogues or derivatives for therapeutic use is also emphasised by recent work that has shown dipyridamole can act as an effective inhibitor of hypoxanthme uptake in selected tumour cell lines indicating that dipyridamole and like compounds have a potential for blocking hypoxanthme rescue based on uptake of extracellular purmes such as hypoxanthme to counteract the cytotoxic effect of certain antifolate drugs such as lometrexol which normally act by inhibiting de novo puπne biosynthesis withm target cells. Further information and data about this aspect, and about other bioactive effects including effects relating to a potential for combating multidrug resistance, are presented m a paper by R. N. Turner, G. W. Aherne and N. J. Curtin entitled "Selective potentiation of lometrexol growth inhibition by dipyridamole through cell-specific inhibition of hyposanthine salvage", Bri t . Journal of Cancer (1997), 7_6 (10), 1300-1307, and m reports by P. G. Smith et al "The potentiation of the multi-targeted antifolate (LY231514: MTA) by dipyridamole), Proc . Amer . Assoc . Cancer Res . (1998), 3_9, 2936 and by E. Marshman et al "Dipyridamole selectivity potentiates antipurme antifolates in human tumour cell lines but not normal tissue targets of dose-limitmg toxicity", Proc . Amer . Assoc . Cancer Res . (1998), 3_9, 4143, the contents of which are incorporated herein by reference. More specifically, from one aspect, the present invention provides pyπmidopyrimidme compounds constituting dipyridamole analogues for use in therapy as agents for modulating or inhibiting transport of nucleosides or purmes across cell membranes, said compounds being compounds having the general structural formula I or pharmaceutically acceptable salts thereof, characterised in that in structural formula I Ri is chloro and R 3 is diethanolamino, or Ri and R 3 are identical and are selected from allyl, halo, diethanolamino, solketalo and a group having the formula -0-R z or -NHR Z , R z being selected from alkyl, hydroxyalkyl, alkoxyalkyl, dialkoxyalkyl and 2-oxo-alkyl wherein the or each alkyl and/or alkoxy moiety has less than six carbon atoms, and R 2 and R are identical and are selected from piperidino, N-tetrahydroisoquinolyl , and a benzylamino group having the structural formula II where R 5 is H, or an optionally substituted alkyl or benzyl group, and Re and R 7 represent H or optional substituents in the aromatic nucleus selected from halo, alkyl, alkoxy, hydroxy, trifluoromethyl, azido, cyano, nitro, carboxyl, carboxylic ester, amino or a substituted amino NR x R y where R x and R y each represent hydrogen or alkyl, subject to the provisos that (a) if Ri and R 3 are both chloro or diethanolamino, R 2 and R4 are not both benzylamino, i.e. R 2 and R 4 do not correspond to structure II with R 5 , R 6 and R 7 each being hydrogen, and (b) if R 2 and R are both piperidino, R x and R 3 are not both chloro, diethanolamino, solketalo or (2 , 3-dιmethoxy) propoxy . From another aspect, the invention also resides m the use of a pyrimidopyπmidme compound as herein defined for the manufacture of a medical preparation for use m therapy for inhibiting membrane nucleoside or purme transport, such transport inhibition constituting an element of a therapeutic treatment, said compound providing the active transport inhibiting agent and being a pyrimidopyπmidme having the general formula I or a pharmaceutically acceptable salt and/or prodrug form thereof, characterised m that m structural formula I Ri is chloro and R 3 is diethanolamino, or Ri and R 3 are identical and are selected from allyl, halo, diethanolamino, solketalo and a group having the formula -0-R z or -NHR Z , R z being selected from alkyl, hydroxyalkyl, alkoxyalkyl, dialkoxyalkyl and 2-oxo-alkyl wherein the or each alkyl and/or alkoxy moiety has less than six carbon atoms, and R 2 and R 4 are identical and are selected from piperidino, N-tetrahydroisoqumolyl, and a benzylamino group having the structural formula II where R 5 is H, or an optionally substituted alkyl or benzyl group, and R 6 and Rη represent H or optional substituents m the aromatic nucleus selected from halo, alkyl, alkoxy, hydroxy, tπfluoromethyl , azido, cyano, nitro, carboxyl, carboxylic ester, ammo or a substituted ammo NR x R y where R x and R y each represent hydrogen or alkyl, subject to the provisos that (a) if Ri and R 3 are both chloro or diethanolamino, R 2 and R 4 are not both benzylamino, i.e. R 2 and R 4 do not correspond to structure II with R 5 , R 6 and R 7 each being hydrogen, and (b) if R 2 and R4 are both piperidino, Ri and R 3 are not both chloro, diethanolamino, solketalo or (2 , 3-dιmethoxy) propoxy . The term solketalo is used herein to denote the group 2 , 2-dιmethyl-l , 3-dιoxolane-4-methoxy . When Ri and/or R is halo, this will preferably be chloro . Also, m preferred embodiments, when R 2 and R 4 are piperidino, R_ and R 3 will be selected from allyl, methoxy, ethoxy, n-propoxy, iso-propoxy, iso-butoxy, 3- methylbutoxy, 2-oxo-n-propoxy, 2 , 2-diethoxy-n-propoxy, (2-methoxy-l-methyl) ethoxy, 2-methoxyethoxy, 2-hydroxy- propoxy, 2-hydroxyethoxy and 3-hydroxypropoxy; when R 2 and R 4 are N-tetrahydroisoquinolyl, Ri and R 3 will each be selected from diethanolamino and chloro; and when R 2 and R 4 are each a benzylamino group of structural formulae II, Ri and R 3 will be selected from 2-methoxyethoxy, propoxy, 2-hydroxypropoxy, diethanolamino, solketalo, chloro, 2- hydroxyethoxy and 3-hydroxypropoxy . In most of the preferred embodiments that are considered to be of greatest interest R 2 and R are in fact each provided by a benzylamino group of formula II, and preferably at least one of R 6 and R 7 will be alkoxy, especially methoxy, which will most preferably be substituted in the 4-position but which can alternatively or additionally (in disubstituted derivatives) be substituted in the 3-position. When R 5 is alkyl, it is preferably methyl. In general, all alkyl groups when present as such, or as a moiety in other groups such as alkoxy, will be lower alkyl groups composed of 1-6 carbon atoms, preferably 1-5 carbon atoms, and more usually 1-4 carbon atoms with Ci, C 2 and C 3 often being of particular interest . In the development of this invention the dipyridamole analogue compounds prepared have been tested for their ability to modulate or inhibit nucleoside transport by measuring the percentage inhibition of thymidine uptake into L1210 cells growing in culture for a given concentration of compounds in the absence of, and in the presence of, the protein AGP. The compounds of this invention that are of special interest possess significant nucleoside transport inhibitory activity which is largely retained in the presence of AGP, and as already indicated they thereby provide potentially very useful therapeutic agents for use n conjunction with other cytotoxic drugs, especially in connection with cancer chemotherapy. The compounds of this invention will generally have a lower AGP binding affinity than dipyridamole itself. Within the series of dipyridamole analogue compounds in accordance with the invention wherein there are benzylamino groups conforming to structural formulae II, compounds of particular interest include compounds where the combination of substituents R 5 , R 6 and R 7 is selected from the following combinations: H 4-OMe H Me 4-OMe H H 4-OMe 3-OMe Me 4-OMe 3-OMe H H H Me H H benzyl H H H 4-CF 3 H Examples of specific compounds within this series that are of interest include (Al) 2 , 6-d - (3-hydroxypropoxy) -4 , 8-dι- { N 4-methoxy- benzyl-IV-methylammo) pyrimidopyπmidme (A2) 2 , 6-bιs-dιethanolammo-4 , 8-dι- ( 4-methoxybenzyl- amino) pyrimidopyπmidme (A3 ) 2 , 6-bis-diethanolamino-4 , 8-bis- (3, 4-dιmethoxy- benzylammo) pyπmidopyrimidme (A4 ) 2 , 6-dι- (2-hydroxypropoxy) -4 , 8-dι- ( 4-methoxybenzyl- ammo) pyrimidopyπmidme (A5) 2, 6-dι (-3-hydroxypropoxy) -4, 8-dι (-4-methoxy- benzylammo) pyrimidopyπmidme (A6) 2, 6-dι- (2-hydroxyethoxy) -4, 8-dι- (IV-4-methoxy- benzyl-W- ethylammo) pyπmidopyrim d ne (A7 ) 2-chloro-6-diethanolamino-4 , 8-bιs [ (3, 4-dιmethoxy- benzyl) ammo] pyπmidopyrimidme (A8 ) 2 , 6-dι (-3-hydroxypropoxy) -4,8-bιs[(-3, 4-dιmethoxy- benzyl) -N-methylammo] pyπmidopyrimidme (A9) 2 , 6-bιs (diethanolamino) -4 , 8-dι ( 4-chlorobenzyl- ammo) pyπmidopyrimidme (A10) 2, 6-dι- (3-hydroxypropoxy) -4, 8-dι- (IV-benzylmethyl- ammo) pyπmidopyrimidme (All) 2, 6-dι (-2-hydroxyethoxy) -4, 8-dι (iV-methyl- benzylamino) pyrimidopyπmidme (A12) 2, 6-dι (-2-methoxyethoxy) -4, 8-dιbenzylammo- pyrimidopyrimidme (A13) 2, 6-dι- (2-methoxyethoxy) -4, 8-dι- (_V-benzyl-Λ7-methyl- ammo) pyrimidopyπmidme (A14) 2 , 6-dιsolketalo-4 , 8-dιbenzylammopyπmιdo- pyπmidme (A15) 2, 6-bιs-dιethanolammo-4 , 8-dι- ( -trιfluoromethyl- benzylammo) pyrimidopyπmidme (A16) 2, 6-dι (-2-methoxyethoxy) -4, 8-bιs (dibenzylammo) pyrimidopyπmidme (A17 ) 2 , 6-dιpropoxy-4 , 8-dι- (_V-benzyl-_\7-methylamιno) - pyrimidopyπmidme (A18) 2, 6-dι (-2-hydroxyethyl) ammo-4, 8-dι ( 4 - methoxybenzyl ) ammopyπmidopyrimidme (A19) 2, 6-dι (-2-hydroxyethylammo) -4, 8-dιbenzyl- ammopyrimidopyrimidme (A20) 2, 6-bιs-dιethanolammo-4, 8-dι- (N-methyl-iV- [4- methoxybenzyl] ) ammopyrimidopyπmidme (A21) 2, 6-dι- (2-hydroxyethyl) ammo-4, 8-bιs- (3, 4- dimethoxybenzyl) ammopyrimidopyπmidme (A22) 2, 6-Dι- (3-hydroxypropoxy) -4, 8-dι- ( N- [4- methoxybenzyl] -ΛJ-methyl) ammopyrimidopyπmidme (A23) 2, 6-Dι- (2-hydroxyethoxy) -4, 8-dι- (iV-benzyl-iV- methyl) ammopyrimidopyπmidme It has been found that in this 4 , 8-dιbenzylammo series of compounds, nucleoside transport inhibitory activity is usually enhanced by one or more alkoxy substituents, preferably methoxy substituents, and/or by N-methylation of the benzylamino group. Also, in this , 8-dibenzylamino series at least one of Ri and R 3 will usually be selected from diethanolamino, 2-hydroxypropoxy and 3-hydroxypropoxy in the most preferred compounds. When R 2 and R 4 are N-tetrahydroisoquinolyl, in a presently preferred embodiment Ri and R 3 are both diethanolamino. In the series of compounds in which R 2 and R are provided by a piperidino group, compounds of particular interest include (Bl) (2-hydroxypropoxy) -4 , 8-dipiperidino- pyrimidopyrimidine (B2 ) ( 3-hydroxypropoxy) -4, 8-dipiperidino- pyrimidopyrimidine (B3 ) (2-methoxyethoxy) -4, 8-dipiperidino- pyrimidopyrimidine (B4) (2-hydroxyethoxy) -4, 8-dipiperidino pyrimidopyrimidine (B5) 2 , 6-bis [2 , 2-diethoxy] -/_-propoxy-4, 8-dipiperidino- pyrimidopyrimidine (B6) 2 , 6-di [2-oxo] -n-propoxy-4 , 8-dipiperidino- pyrimidopyrimidine (B7 ) 2 , 6-dimethoxy-4 , 8-dipiperidinopyrimidopyrimidine (B8 ) 2 , 6-diethoxy-4 , 8-dipiperidinopyrimidopyrimidine (B9) 2, 6-di-3-methylbutoxy-4 , 8-dipiperidino- pyrimidopyrimidine (BIO) (2-methoxy-l-methyl) ethoxy-4, 8-dipiperidino pyrimidopyrimidine (Bll) 2,6-diallyl-4, 8 -dipiperidinopyrimidopyrimidine (B12 ) 2 , 6-di-n-propoxy-4 , 8-dipiperidinopyrimidopyrimidine (B13) 2 , 6-di-iso-propoxy-4 , 8-dipiperidinopyrimido- pyrimidine (B14 ) 2 , 6-di-iso-butoxy-4 , 8-dipiperidinopyrimido- pyrimidine The invention also embraces or extends to methods of preparing compounds as hereinbefore defined (including intermediates m some cases), as well as to the therapeutic use of such compounds m treating mammals. At least most of the dipyridamole analogue compounds of this invention can be prepared via 2,4,6,8- tetrachloropyrimidopyπmidme which is a key intermediate or precursor that can be reacted with selected ammes and alcohols sequentially to replace the chloro substituents. In general, the chloro substituents in the 4 and 8 positions are more readily displaced by nucleophiles than the chloro substituents in the 2 and 6 positions so that, for example, an initial treatment of the tetrachloro compound with two equivalents of an amine followed by subsequent treatment with two equivalents of an alcohol can be used to obtain a stepwise replacement of the chloro substituents leading to the production of compounds with two different substituents located respectively m the 4,8 and the 2,6 positions. Further details will become apparent from numerous examples of the preparation of specific compounds hereinafter described. As already indicated, the therapeutic use of the compounds of this invention includes their use for making medical or veterinary preparations or pharmaceutical formulations which will contain an effective nucleoside transport inhibiting amount of the active compound for administration to a patient in conjunction with a cytotoxic drug m order to increase the cytotoxic effectiveness of the latter. Such preparations or formulations may be made up m accordance with any of the methods well known in the art of pharmacy for administration in any suitable manner, for example orally, parenterally (including subcutaneously, intramuscularly or intravenously) , or topically, the mode of administration, type of preparations or formulation and the dosage being generally determined by the details of the associated cytotoxic drug chemotherapy that is to be enhanced or potentiated. Accordingly, the invention also includes pharmaceutical compositions or preparations, conveniently m unit dosage form, for selective use in conjunction with cytotoxic drugs in antitumor therapy, said compositions or preparations comprising as an active nucleoside transport inhibitory substance a dipyridamole analogue compound as herein specified. In making up such pharmaceutical formulations in the form of sterile liquid preparations for parental use for instance, a predetermined therapeutically effective non-toxic amount of the particular compound concerned may be dissolved in phosphate buffered saline and the preparations may be presented unit dosage form and contained in sealed ampoules ready for use. In general, at least in aqueous solution, concentrations not greater than 200mg/ml will be preferred, but the amount and dosage routine required for optimum effectiveness will of course vary and is ultimately at the discretion of the medical or veterinary practitioner treating the mammal concerned m each particular case. In using the nucleoside transport inhibiting compounds of the present invention in conjunction with cytotoxic drugs, m some cases the compound and the cytotoxic drug may be administered sequentially, whilst in other cases they may be administered simultaneously. In the latter case, it may be possible for them conveniently to be incorporated m the same pharmaceutical formulation or composition. As mentioned, the compounds according to this invention have at least a potential for use as nucleoside transport inhibitors, and m vi tro tests hereinafter described have demonstrated positive pharmacological activity which is maintained even the presence of AGP. It is believed that this reflects the activity to be found m vivo m the course of therapeutic clinical use. It will be understood that many of the compounds m accordance with the invention which are herein referred to may be presented, when used as therapeutic agents, in the form of pharmaceutically acceptable salts, especially acid addition salts derived from an acid selected for example from the group comprising: hydrochloric, hydrobromic, sulphuric, nitric, phosphoric, maleic, salicylic, p-toluenesulphonic, tartaric, citric, lactobionic, formic, malonic, pantothenic, succinic, naphthalene-2-sulphonιc, benzenesulphonic, methane- sulphonic and ethanesulphonic . It should also be understood that where reference is made m this specification to compounds of formula I in the context of their use as therapeutic agents such reference should be construed as extending not only to their pharmaceutically acceptable salts but also to other pharmaceutically acceptable bioprecursors (prodrug forms) where relevant. The term "prodrug" is used m the present specification to denote modified forms or derivatives of a pharmacologically active compound which biodegrade m vivo and become converted into said active compound after administration, especially oral or mtravenenous administration, in the course of therapeutic treatment of a mammal. Such prodrugs are commonly chosen because of an enhanced solubility m aqueous media which helps to overcome formulation problems, and also in some cases to give a relatively slow or controlled release of the active agent. A satisfactory prodrug must generally be a water- soluble derivative which is non-toxic and reasonably stable in solution at physiological pH but which will biodegrade or convert, e.g. by enzymatic degradation or by an enviromental pH change, to the active compound at the location required following administration in the course of therapy. For many of the compounds of the present invention, prodrug forms may be provided by carbamate or ammo acid derivatives, e.g. glycme or other ammo-acid carbamate derivatives, or by phosphate derivatives . Phosphate derivatives that are susceptible to enzymic dephosphorylation in vivo will often be preferred, especially water-soluble ammonium or alkali metal phosphate salts. These may be conveniently prepared in many cases from compounds of structural formula I having at least one hydroxyl group substituent amenable to phosphorylation by reacting for example with a dibenzyl phosphonate, preferably in the presence of a tertiary base such as N,_V-diisopropylethylamine . It should also be understood that where any of the compounds referred to can exist in more than one enantiomeric and/or diastereoisomeric form, all such forms, mixtures thereof, and their preparations and uses are within the scope of the invention. DESCRIPTION OF EXAMPLES OF PREFERRED EMBODIMENTS The following examples and description of stages in synthetic routes of preparation of various preferred compounds of interest serve to further illustrate the present invention, but should not be construed m any way as a limitation thereof. In many instances the compounds described are accompanied by an NU reference or identification code number. First, in EXAMPLES 1A and IB, the preparation is described of 2 , 4 , 6, 8-tetrachloropyrιmιdopyrιmιdme and 2 , 6-Dιchloro-4 , 8-dιpιperιdmopyrιmιdopyrιmιdme which are intermediates used in the preparation of many of the other dipyridamole analogues hereinafter described. EXAMPLE 1A 2,4,6, 8-Tetrachloropyrιmιdopyrιmιdme (NU3000) (a) 1st Stage - Preparation of 1,5-Dιsodιum 2,4,6,8- pyrimido [5, 4-d] pyπmidme tetrone Commercially available 2 , 4 , 6, 8-pyrιmιdo [5, 4-d] - pyrimidme tetrone (4.9g, 25mmol) was added to a hot solution of 0.1M NaOH (500ml) and the mixture was stirred with heating until boiling. Hot water (400ml) was added until all the yellow powder dissolved, then the mixture was filtered under suction using hot filtration glassware. After cooling, the product crystallised from the filtrate and was filtered under reduced pressure and dried m va cuo (P 2 O 5 ) . The product was obtained as a bright yellow fluffy solid (6.15g, 98%) . (b) 2nd Stage - Preparation of 2,4,6,8- Tetrachloropyrimidopyrimidme (NU3000) To a solution of phosphorus pentachloride (15g, 72mmol) in phosphorus oxychloπde (125ml, 1.34mol) was added 1, 5-Disodium 2 , 4 , 6, 8-pyrιmιdo [5 , 4-d] pyrimidme tetrone (3g, 12.5mmol) . The mixture was heated under reflux for 20 hours at 140-150°C. Excess of phosphorus oxychloride was removed by distillation under vacuum and the brown residue deposited into crushed ice (60g) . The mixture was immediately filtered, and the resulting solid was washed with water and dried in va cuo (P 2 O 5 ) . This was extracted into chloroform (approximately 200ml) using soxhlet apparatus, and the solvent was removed yielding the title compound as a yellow powder (1.07g, 31%) . δ c (CDCI 3 , 300 MHz) 141.91, 157.84, 165.78; m/z (El) 268 (M + , 80%), 236, 199, 173, 163, 111. EXAMPLE IB 2 , 6-Dιchloro-4 , 8-dιpιperιdmopyrιmιdopyrιmιdme (NU3002 ) Pipeπdme (0.8ml, 8mmol) was added to tetra- chloropyrimidopynmidme (0.54g, 2mmol) n THF (15ml) and the resulting solution was stirred for 10 minutes until a yellow precipitate formed. Water (75ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried m vacuo (P2O 5 ) yielding the title compound as a yellow powder (0.62g, 75%), m.p. 240-241°C, δ H (CDC1 3 , 200 MHz) 1.81 (12H, s, 2x(CH 2 ) 3 ), 4.15 (8H, s br, 2xN(CH 2 ) 2 ); m/z (El) 366 (M + -l), 198. EXAMPLE 2 2, 6-D1 (π) propoxy-4 , 8-dιpιperιdmopyrιmιdopyrιmιdme (NU3064) Sodium metal (0.24g, 10.4mmol) was added to propan- l-ol (6ml) in dry THF (10ml) and stirred until all had dissolved. The solvent was evaporated under a stream of N 2 and the residue was redissolved in dry THF (15ml) . 2 , 6-dιchloro-4 , 8-dιpιperιdmopyπmιdopyrιmιdme (0.367g, lmmol) in dry THF (10ml) was added to the alkoxide and the mixture heated under reflux for 16 hours. After cooling to room temperature water (20ml) was added and the product extracted into ethyl acetate (3 x 40ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as a white crystalline solid (0.173g, 42%), m.p. 127-129°C. Found: C, 63.96; H, 8.36; N, 20.24. C 22 H 34 N 6 O 2 requires C, 63.74; H, 8.27; N, 20.27%. EXAMPLE 3 2, 6-bis (2 ' , 2 ' -Piethylacetal-1-propoxy) -4, 8- dipiperidinopyrimidopyrimidine (NU3065 ) (a) 1st Stage - Preparation of Ethyl pyruvate diethyl acetal Ethyl pyruvate (22ml, 0.19mmol) was dissolved in ethanol (30ml) and to this was added triethyl orthoformate (35ml) and p-toluenesulphonic acid (0.5g) and the mixture stirred at 60°C for 15 minutes. The temperature was slowly increased to 80°C and the ethyl formate produced in the reaction distilled off. After removal of all the ethyl formate (5 hours) the remaining mixture was neutralised with triethanolamine (0.5ml) . Ethanol was removed in va cuo and the remaining liquor distilled under reduced pressure yielding the title compound as a clear colourless liquid (30.78g, 61%), b.p. 80-83°C at 15mm Hg . (b) 2nd Stage - Preparation of 2 , 2-Diethoxypropan-l-ol Ethyl pyruvate diethyl acetal (5.0g, 26.3mmol) in anhydrous THF (10ml) was added dropwise to a suspension of lithium aluminium hydride (l.Og, 26.3mmol) in anhydrous THF (40ml) and the mixture was stirred for 15 minutes. Water (1ml) was added followed by 2M sodium hydroxide (3ml) then a further portion of water (1ml) . The grey suspension turned white and was filtered, washed with THF and the solvent removed in va cuo yielding a pale yellow oil which was purified by distillation under reduced pressure (0.75g, 19%), b.p. 79-81°C at 15mm Hg . (c) 3rd Stage - Preparation of 2 , 6-bιs (2 ' , 2 ' - Dιethylacetal-1-propoxy) -4, 8-dιpιper dmo- pyrimidopyrimidme Sodium metal (0.092g, 4mmol) was added to 2, 2, diethylacetal propan-1-ol (0.592g, 4mmol) in dry THF (4ml) and the mixture was stirred under nitrogen for 6 hours when all the sodium had dissolved. 2 , 6-dιchloro- 4 , 8-dιpιpeπdmopyrιmιdopyrιmιdme (0.367g, lmmol) m dry THF (10ml) was added and the mixture heated under reflux for 48 hours. After cooling to room temperature, water (40ml) was added and the crude product was extracted into ethyl acetate (4x40ml) . The combined extracts were dried (MgSθ 4 ), filtered and the solvent removed m va cuo . Purification by column chromatography on silica gel, with petrol: ethyl acetate (5:1) as eluent then recrystallisation from petrol afforded the title compound as an off-white solid (0.197g, 33%), m.p. 83-84°C. Found: C, 61.01; H, 8.45; N, 14.08. C 3 oH 5 oN 6 0 6 requires C, 60.99; H, 8.53; N, 14.23 %. EXAMPLE 4 2, 6-Dι (-2-oxopropoxy) -4, 8-dιpιperιdmopyrιmιdopyrιmιdme (NU3066) First, 2, 6-bis (2' , 2 ' -dιethylacetal-1-propoxy) -4, 8- dipiperidmopyrimidopyπmidme (0.10g, 0.17mmo1 ) was stirred in aqueous acetic acid (0.5ml) at room temperature, and glacial acetic acid added until all had dissolved. The mixture was then stirred for 30 minutes. The solvent was removed by evaporation and the residue was further dried in va cuo . The title compound was recovered as a white solid (0.064g, 85%), m.p. 188-189°C. EXAMPLE 5 2 , 6-Dιmethoxy- 4 , 8 -dιpιperιdmopyrιmιdopyrιmιdme (NU3067 ) 2 , 6-Dιchloro- 4 , 8 -dιpιperιdmopyrιmιdopyrιmιdme ( 0 . 184 g , 0 . 5mmol ) was dissolved in dry THF ( 15ml ) , then added to freshly prepared sodium methoxide (4.1ml, 1.22M, 5mmol) in dry THF (5ml) under a N 2 atmosphere, and the mixture heated under reflux for 20 hours. After cooling to room temperature water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as a yellow crystalline solid (0.083g, 46%), m.p. 130-131°C. Found: C, 59.41; H, 7.27; N, 22.17. Cι 8 H26N 6 θ2 requires C, 60.32; H, 7.31; N, 23.44%. EXAMPLE 6 2 , 6-Diethoxy-4 , 8-dipiperidinopyrimidopyrimidine (NU3068 ) Sodium metal (0.115g, 5mmol) was added to ethanol (0.23g, 5mmol) in dry THF (5ml) and stirred until all had dissolved. Then, 2 , 6-dichloro-4 , 8-dipiperidinopyrimido- pyrimidine (0.184g, 0.5mmol) dissolved in dry THF (10ml) was added to the alkoxide and the mixture was heated under reflux for 18 hours. After cooling to room temperature water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as an orange crystalline solid (0.167g, 84%), m.p. 142-143°C. Found: C, 62.11; H, 7.81; N, 21.34. C20H 3 0N 6 O 2 requires C, 62.15; H, 7.82; N, 21.74%. EXAMPLE 7 2 , 6-Di-iso-propoxy-4 , 8-dipiperidinopyrimidopyrimidine (NU3069) Sodium metal (0.115g, 5mmol) was added to propan-2- ol (0.3g, 5mmol) in dry THF (5ml) and stirred until all had dissolved. 2 , 6-dichloro-4 , 8-dipiperidinopyrimido- pyrimidine (0.184g, 0.5mmol) dissolved in dry THF (10ml) was added to the alkoxide and the mixture heated under reflux for 96 hours. After cooling to room temperature water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in vacuo . Recrystallisation from methanol/water yielded the title compound as a yellow crystalline solid (0.24g, 58%), m.p. 167-169°C. Found: C, 63.23; H, 8.32; N, 19.78. C 22 H34N6O2 requires C, 63.74; H, 8.27; N, 20.27 %. EXAMPLE 8 2 , 6-Pi- (3' -methylbutoxy) -4 , 8-dipiperidinopyrimido- pyrimidine (NU3070) Sodium metal (0.115g, 5mmol) was added to 3- methylbutan-1-ol (0.44g, 5mmol) in dry THF (5ml) and stirred until all had dissolved. 2 , 6-dichloro-4 , 8- dipiperidinopyrimidopyrimidine (0.184g, 0.5mmol) dissolved in dry THF (10ml) was added to the alkoxide and the mixture heated under reflux for 72 hours. After cooling to room temperature, water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in vacuo . Recrystallisation from methanol/water yielded the title compound as a yellow crystalline solid (0.148g, 63%), m.p. 105-106°C. Found: C, 66.73; H, 8.80; N, 17.48. C2 6 H 42 N. 3 O 2 requires C, 66.35; H, 8.99; N, 17.86%. EXAMPLE 9 2 , 6-Pi- { 2 ' -methylpropoxy) -4 , 8-dipiperidinopyrimido- pyrimidine (NU3071) Sodium metal (0.115g, 5mmol) was added to 2- methylpropan-1-ol (0.37g, 5mmol) in dry THF (5ml) and stirred until all had dissolved. 2 , 6-dichloro-4 , 8-di- piperidinopyrimidopyrimidine (0.184g, 0.5mmol) dissolved in dry THF (10ml) was added to the alkoxide and the mixture heated under reflux for 42 hours. After cooling to room temperature, water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ) , filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as a yellow crystalline solid (0.122g, 54%), m.p. 114-116°C. EXAMPLE 10 2 , 6-Pi-allyloxy-4 , 8-dipiperidinopyrimidopyrimidine (NU3072) Sodium metal (0.115g, 5mmol) was added to allyl alcohol (0.291g, 5mmol) in dry THF (5ml) and stirred until all had dissolved. 2 , 6-dichloro-4 , 8-dipiperidino- pyrimidopyrimidine (0.184g, 0.5mmol) dissolved in dry THF (10ml) was added to the alkoxide and the mixture heated under reflux for 72 hours. After cooling to room temperature, water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as a white crystalline solid (0.079g, 40%), m.p. 109-110°C. EXAMPLE 11 2 , 6-Pi ( 1' -methoxy-2' -methyl) ethoxy-4 , 8-dipiperidino- pyrimidopyrimidine (NU3074) Sodium metal (0.115g, 5mmol) was added to 1- methoxy-2-propanol (0.45g, 5mmol) in dry THF (5ml) and stirred until all had dissolved. 2 , 6-dichloro-4 , 8- piperidinopyrimidopyrimidine (0.184g, 0.5mmol) dissolved in dry THF (10ml) was added to the alkoxide and the mixture heated under reflux for 72 hours. After cooling to room temperature, water (20ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed m va cuo . Purification by column chromatography on silica gel, with petrol: ethyl acetate (5:1) as eluent, gave the title compound as a cream coloured crystalline solid (0.053g, 22%), m.p. 91-93°C. Found: C, 60.67; H, 7.94; N, 17.16. C 24 H 38 N 6 0 4 requires C, 60.74; H, 8.07; N, 17.71%. EXAMPLE 12 2, 6-Dι (2 f -hydroxypropoxy) -4, 8-dιpιperιdιnopyr m do- pyrimidme (NU3077) (a) 1st Stage - Preparation of 2 , 6-Dι [ -2 ' - O- [ ( 4 ' ' - methoxybenzyl) propoxy] -4 , 8-dιpιperιdmopyrιmιdo- pyrimidme Sodium metal (0.115g, 5mmol) was added to 2-0- (4- methoxybenzyl) propan-1-ol (0.98g, 5mmol) m dry THF (5ml) and stirred at room temperature under nitrogen until all had dissolved. 2 , 6-dιchloro-4 , 8-dιpιperιdmopyπmιdo- pyπmidme (0.184g, 0.5mmol) in dry THF (10ml) was added and the mixture heated under reflux for 48 hours. After cooling to room temperature water (20ml) was added and the crude product extracted into ethyl acetate (4 x 15ml) . The organic layers were combined, dried (MgS0 4 ) , filtered and solvent removed in vacuo yielding an orange mobile oil. Purification by column chromatography with petrol: ethyl acetate (6:1) and Hunig' s Base (1.5%) as eluent afforded the title compound. m/z (El) 686 (M + , 2%) . (b) 2nd Stage - Preparation of 2 , 6-Dι (2 ' -hydroxypropoxy) -4 , 8-dιpιperιdmopyrιmιdopyrιmιdme 2,6-Dι[-2'-0-(4'' -methoxybenzyl) propoxy] -4 , 8-dι- piperidmopyridimidopyπmidme dissolved m methanol (40ml) was stirred in an atmosphere of hydrogen in the presence a catalytic quantity of palladium/carbon for 4 hours. The mixture was filtered under reduced pressure through celite, washed with methanol and then the solvent was removed m va cuo . Purification by column chromatography with petrol : ethyl acetate (3:1) and Hunig's base (1%) as eluent afforded the title compound as a white crystalline solid (0.027g, 10%), m.p. 128- 129°C. Found: C, 59.31; H, 7.62; N, 18.24. C 22 H 34 N 6 θ 4 requires C, 59.17; H, 7.67; N, 18.82%. EXAMPLE 13 2 , 6-Dι (3' -hydroxypropoxy) -4 , 8-dιpιperιdιnopyπmιdo- pyrimidme (NU3085) 1,3-Propane diol (0.73ml, lOmmol) was dissolved in dry THF (10ml), added to sodium hydride (0.24g, lOmmol) and the mixture was stirred at room temperature for 6 hours . 2 , 6-dιchloro-4 , 8-dιpιperιdmopyrιmιdopyπmιdme (0.184g, 0.5mmol) in dry THF (25ml) was added and the mixture heated under reflux 72 hours. After cooling to room temperature, water (30ml) was added and the product extracted into ethyl acetate (4 x 20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and solvent removed m vacuo . Purification was carried out by column chromatography on silica gel, with dichloromethane : methanol (95:5) as eluent. Subsequent recrystallisation from methanol/water gave the title compound as a cream solid (0.115g, 51%), m.p. 154-156°C. Found: C, 59.23; H, 7.72; N, 18.79. C 2 2H 3 4N 6 θ 4 requires C, 59.17; H, 7.67; N, 18.82 %. EXAMPLE 14 2 , 6-Dι [ 2 ' -hydroxyethoxy) -4 , 8-dιpιper d nopynm do- pyrimidme (NU3086) Ethylene glycol (0.56ml, lOmmol) was dissolved m dry THF (10ml), then added to sodium hydride (0.24g, lOmmol) and stirred at room temperature for 6 hours. 2, 6-dιchloro-4, 8-dιpιperιdmopyrιmιdopyrιmιdme ( 0.184g, 0.5mmol) dry THF (25ml) was added and the mixture heated under reflux for 96 hours. After cooling to room temperature, water (30ml) was added and the product extracted into ethyl acetate (4x20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and solvent removed in va cuo . Purification was carried out by column chromatography on silica gel, with dichloromethane : methanol (95:5) as eluent. This gave the title compound as an off-white solid (O.lg, 45%), m.p. 148-150°C. Found: C, 57.54; H, 7.21; N, 19.41. C 20 H 30 6 O 4 requires C, 57.40; H, 7.23; N, 20.08%. EXAMPLE 15 2 , 6-Pi (-2 ' -methoxyethoxy) -4 , 8-dipiperidinopyrimido- pyrimidine (NU3093) 2-Methoxyethanol (0.38g, 5mmol) was dissolved in dry THF (5ml) and added to sodium hydride (0.12g, 5mmol) and stirred for 8 hours at room temperature. 2,6- dichloro-4 , 8-dipiperidinopyrimidopyrimidine (0.184g, 0.5 mmol) in dry THF (10ml) was added to this and the mixture heated under reflux for 32 hours . After cooling to room temperature, water (30ml) was added and the product extracted into ethyl acetate (4 x 20ml), the organic layers combined, dried (MgS0 ) , filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as a white solid (0.076g, 34%), m.p. 127-128°C. Found C, 59.31; H, 7.60; N, 18.80. C 22 H 34 N 6 O 4 requires C, 59.17; H, 7.67; N, 18.82%. EXAMPLE 16A 2, 6-Pichloro-4, 8-di- (IV-1,2,3, 4-tetrahydroisoquinolyl) - pyrimidopyrimidine (NU3075) To a solution of 2 , 4 , 6, 8-tetrachloropyrimido- pyrimidine (0.54g, δ.Ommol) in THF (50ml) was added a solution of 1 , 2 , 3, 4-tetrahydroisoquinoline (1.0ml) in THF (15ml) dropwise over 10 minutes. The mixture was stirred for 12 hours at 25°C, the resultant solid was removed by filtration. The filtrate was evaporated under reduced pressure to afford a brown solid. Chromatography on silica gel, employing petrol :EtOAc (8:2) as eluent, afforded the title compound as a pale brown powder (0.27g, 7%) . EXAMPLE 16B 2 , 6-bis-Piethanolammo- 4 , 8-dι- { N- l , 2 , 3 , 4-tetrahydroιso- qu nolyl) pyrimidopyrimidine (NU3080) and 2-Chloro-6- diethanolammo-4 , 8-dι- ( N- l , 2 , 3, 4-tetrahydroιsoqumolyl ) - pyrimidopyrimidine (NU3082) A suspension of 2 , 6-dιchloro-4 , 8-bιs- { N- l , 2 , 3, 4- tetrahydroisoqumolyl) pyrimidopyrimidine (0.20g, 0.4mmol) in diethanolamme (5ml) was stirred under nitrogen at 120°C for 3 hours. After cooling, water (30ml) was added and the reaction mixture was stood at 4°C for 48 hours, whereupon a solid slowly deposited. The mixture was extracted with ethyl acetate (2 x 30ml), and the combined organic layers were washed with water (30ml), dried (MgS0 ) and evaporated m va cuo to afford a pale yellow solid. Chromatography on silica gel, utilising CHCl 2 :MeOH (93:7) as eluent, afforded the title compound 2,6-bιs- diethanolamino-4 , 8-dι- { N- l , 2 , 3, 4-tetrahydroιsoqumolyl) - pyrimidopyrimidine (0.04g, 17%) . A second product recovered was identified as 2-chloro-6-dιethanolamιno- 4,8-dι-(Λ-l,2,3, 4-tetrahydro soquιnolyl) pyπmido- pyrimidme (0.04g, 19%). EXAMPLE 17 2 , 6-bis ( Piethanolammo) -4 , 8-dι [ ( 4 ' -methoxybenzyl) ammo] - pyrimidopyrimidine (NU3076) (a) 1st Stage - Preparation of 2 , -Pιchloro-4 , 8-dι [ ( 4 ' - methoxybenzyl) ammo] pyrimidopyrimidine 4-Methoxybenzylamιne (0.27ml, 2mmol) was added to tetrachloropyrimidopyπmidme (0.135g, 0.5mmol) m THF (10ml) and stirred for 10 minutes until a yellow precipitate formed. Water (40ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in va cuo (P 2 O 5 ) yielding the title compound as a yellow powder (0.218g, 93%), m.p. 186-188°C. (b) 2nd Stage - Preparation of 2,6-bis (Diethanolamino) -4 , 8-di [ (4 ' -methoxybenzyl) amino] pyrimido pyrimidine Diethanolamine (1ml) was added to 2 , 6-dichloro-4 , 8- di [ ( 4 ' -methoxybenzyl ) amino] pyrimidopyrimidine ( 0.118g, 0.25mmol) and heated for 18 hours at 110°C. After cooling to room temperature water (40ml) was added to give a precipitate which was filtered under reduced pressure. Recrystallisation of the crude material from methanol afforded the title compound as a yellow fluffy solid (0.047g, 31%), m.p. 204-205°C. Found: C, 59.40; H, 6.37; N, 18.40. C 3 0H40N8O6 requires C, 59.20; H, 6.37; N, 18.41%. EXAMPLE 18 { R, R) -2 , 6-bis { 2 ' , 2 ' -Dimethyl- 1 ' , 3 ' -dioxolane-4 ' -methoxy) - 4 , 8-dibenzylamino pyrimidopyrimidine (NU3078) (a) 1st Stage - Preparation of 1, 2 ; 5, 6-Di-O- isopropylidene-D-mannitol Anhydrous zinc chloride (pre-dried over P 2 O 5 in va cuo, 32g, 0.235mmol) was dissolved into freshly dried (B 2 0 3 ) and distilled acetone (200ml) . The resulting solution was cooled to room temperature under anhydrous conditions. D-Mannitol (20g, O.llmol) was added portionwise and the reaction mixture stirred at room temperature. After 24 hours a fresh solution of potassium carbonate (40g) in water (40ml) was added and stirred vigorously. The resulting precipitate was removed with portions of dichloromethane, the combined filtrate and washings were evaporated under reduced pressure to yield a white wet solid. This was dissolved m dichloromethane (100ml) washed with water (100ml), saturated NaHC0 3 (100ml) then dried (Na 2 S0 ) , filtered and evaporated to give a white solid. Recrystallisation from n-hexane/ethyl acetate afforded the title compound as a white solid (9.23g, 20%), m.p. 118-120°C. (b) 2nd Stage - Preparation of 1 , 2-O-Isopropylιdene- (S) -n-glycerol [Solketal (S)] 1, 2 : 5 , 6-Dι-O-ιsopropylιdene-D-mannιtol (5g, 19mmol) was added portionwise to a stirred solution of sodium periodate (5.97g, 28mmol) m water (75ml), cooled m an ice bath. After 90 minutes, pre-cooled ethanol (110ml) was added causing precipitation of a white solid. The solid was removed by filtration into a cooled flask. Sodium borohyπde (1.5g, 40mmol) was added portionwise to the cooled filtrate. The mixture became viscous and a white precipitate formed which was stirred at room temperature for 2.5 hours. The precipitate was filtered and the filtrate reduced m va cuo (temp less than 25°C) . Distillation at water pump afforded the title compound as a clear colourless liquid (2.56g, 99%) . (c) 3rd Stage - Preparation of 2 , 6-Dιchloro-4 , 8- dibenzylammopyrimidopyrimidme Benzylamme (0.22ml, 2mmol) was added to tetrachloropyrimidopyπmidme (0.135g, 0.5mmol) in THF (10ml) and stirred for 10 minutes until a yellow precipitate formed. Water (40ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in va cuo (P 2 O 5 ) yielding the title compound as a yellow powder (0.176g, 86%), m.p. 229-230°C. (d) 4th Stage - Preparation of { R , R) -2 , 6-bιs (2 ' , 2 ' - Dιmethyl-1' , 3 ' -dιoxolane-4 ' -methoxy) -4, 8-dιbenzyl- amino pyrimidopyrimidine Sodium metal (O.llδg, 5mmol) was added to (S) solketal (0.99g, 7.5mmol) m dry THF (10ml) and stirred under reflux conditions for 48 hours. 2 , 6-dιchloro-4 , 8- dibenzylammopyπmidopyrimidme (0.103g, 0.25mmol) in dry THF (15ml) was added and the mixture was heated under reflux for 54 hours. After cooling to room temperature water (20ml) was added and the product was extracted into ethyl acetate (4x15ml) . The organic layers were combined, dried (MgS0 4 ) , filtered and solvent removed in va cuo yielding the crude product as a yellow oil. Recrystallisation from petrol/ethyl acetate afforded the title compound as a cream solid (0.051g, 34%), m.p. 113- 115°C. Found C, 63.21; H, 6.21; N, 13.83. C 32 H 38 N 6 θ 6 requires C, 63.77; H, 6.36; N, 13.94%. EXAMPLE 19 2 , 6-bis (Diethanolamino) -4 , 8-dι [ ( 4 ' -trifluoromethyl- benzyl) ammo] pyrimido pyrimidme (NU3079) (a) 1st Stage - Preparation of 2 , 6-Pιchloro-4 , 8-dι [ ( 4 ' - trifluoromethylbenzyl ) ammo] pyrimidopyrimidine 4-Trιfluoromethylbenzylamme (0.28ml, 2mmol) was added to tetrachloropyrimidopyπmidme (0.135g, 0.5mmol) in THF (10ml) and stirred for 10 minutes until a yellow precipitate formed. Water (40ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in va cuo (P 2 0 5 ) yielding the title compound as an orange powder (0.248g, 91%), m.p. 284-285°C. (b) 2nd Stage - Preparation of 2 , 6-bιs (Diethanolamino) - 4 , 8-dι [ ( 4 ' -trifluoromethylbenzyl) ammo] pyrimido pyrimidme Diethanolamme (1ml) was added to 2 , 6-dιchloro-4 , 8- di [ (4 ' -trifluoromethylbenzyl) ammo] pyrimidopyrimidine (0.136g, 0.25mmol) and heated for 18 hours at 110°C. After cooling to room temperature water (40ml) was added giving a precipitate which was filtered under reduced pressure. Recrystallisation from dichloromethane afforded the title compound as a pale yellow solid (0.159g. 93%), m.p. 194-196°C. Found: C, 52.57; H, 4.79; N, 15.90. C 3 oH 34 N 8 θ 4 F 6 requires C, 52.63; H, 4.73; N, 15.67%. EXAMPLE 20 2 -chloro- 6-diethanolamino-4 ,8-bis[(3',4' -dimethoxy- benzyl ) amino] pyrimidopyrimidine (NU3081 ) (a) 1st Stage - Preparation of 2 , 6-Pichloro-4 , 8- bis [ { 3 ' , 4 ' -dimethoxybenzyl) amino] pyrimidopyrimidine 3 , 4-Pimethoxybenzylamine (0.334ml, 2mmol) was added to tetrachloropyrimidopyrimidine (0.135g, 0.5mmol) in THF (10ml) and stirred for 10 minutes until a yellow precipitate formed. Water (40ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in va cuo (P 2 O 5 ) yielding the title compound as a yellow powder (0.221g, 83%), m.p. 211-213°C. (b) 2nd Stage - Preparation of 2-chloro-6- diethanolamino-4 ,8-bis[(3',4' -dimethoxybenzyl) - amino] pyrimidopyrimidine Piethanolamine (1ml) was added to 2 , 6-dichloro-4 , 8- di [ (3' , 4 ' -dimethoxybenzyl) amino] pyrimidopyrimidine (0.118g, 0.25mmol) and heated for 18 hours at 110°C. After cooling to room temperature water (40ml) was added giving a precipitate which was filtered under reduced pressure. Recrystallisation of the crude material from ethyl acetate/petrol afforded the title compound as a yellow fluffy solid (0.047g, 31%), m.p. 101-103°C. Found: C, 55.69; H, 5.85; N, 16.66. C 28 H 34 N0 6 C1 required C, 56.04; H, 5.71; N, 16.34%. EXAMPLE 2 1 2 , 6-bis ( Piethanolamino) -4, 8-di [ (4' -chloro- benzyl ) amino] pyrimido pyrimidine (NU3083) (a) 1st Stage - Preparation of 2 , 6-dichloro-4 , 8-di [ ( 4- chlorobenzyl ) amino] pyrimidopyrimidine 4-Chlorobenzylamine (0.255ml, 2mmol) was added to tetrachloropyrimidopyrimidine (0.135g, 0.5mmol) in THF (10ml) and stirred for 10 minutes until a yellow precipitate formed. Water (40ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in va cuo (P 2 O 5 ) yielding the title compound as a yellow powder (0.162g, 68%), m.p. 299-301°C. (b) 2nd Stage - Preparation of 2 , 6-bis (Piethanolamino) - 4, 8-di [ ( 4 ' -chlorobenzyl) amino] pyrimido pyrimidine Piethanolamine (2ml) was added to 2 , 6-dichloro-4 , 8- di [ ( 4 ' -chlorobenzyl ) amino] pyrimidopyrimidine ( 0.246g, 0.5mmol) and heated for 18 hours at 110°C. After cooling to room temperature water (40ml) was added forming a precipitate which was filtered under reduced pressure. Filtration of the crude reaction mixture from hot ethyl acetate afforded the title compound as a yellow solid (O.lβg, 51%), m.p. 223-224°C. Found: C, 54.45; H, 5.55; N, 18.01. C 28 H 34 N 8 θ 4 Cl 2 requires C, 54.46; H, 5.55; N, 18.15%. EXAMPLE 22 2, 6-bis (Piethanolamino) -4, 8 -bis [ (3' , 4' - dimethoxybenzyl) amino] pyrimidopyrimidine (NU3084 ) Piethanolamine (5ml) was added to 2 , 6-dichloro-4 , 8- di [3' , 4 ' -dimethoxybenzyl) amino] pyrimidopyrimidine (see Example 20) (0.266g, 0.5mmol) and heated for 72 hours at 110°C. After cooling to room temperature water (40ml) was added forming a precipitate which was filtered under reduced pressure. Recrystallisation of the crude material from ethyl acetate afforded the title compound as a pale yellow solid (0.043g, 13%), m.p. 176-179°C. Found: C, 57.20; H, 6.60; N, 16.62. C 32 H 44 N 8 0 8 requires C, 57.47; H, 6.63; N, 16.76%. EXAMPLE 23 2 , 6-Pi { 2 ' -hydroxypropoxy) -4 , 8 -bis (4' -methoxybenzyl- amino) pyrimidopyrimidine (NU3087 Sodium hydride (0.48g, 20mmol) was added to 1,2- propanediol (1.46ml, 20mmol) in dry THF (10ml) and stirred at 40°C for 24 hours until all had dissolved. Then 2,6-dichloro-4,8-bis(4' -methoxybenzylamino) pyrimidopyrimidine (see Example 17) (0.471g, lmmol) in dry THF (30ml) was added to the alkoxide and the mixture heated under reflux for 72 hours. After cooling to room temperature water (30ml) was added and the product extracted with ethyl acetate (4x20ml) . The combined extracts were dried (MgS0 4 ) and the solvent evaporated. Chromatography on silica gel with dichloro- methane :methanol (93:7) and then subsequent recrystallisation from iso-propanol yielded the title compound as a white solid (0.123g, 22%), m.p .190-192°C . Found C, 59.72; H, 6.06; N, 14.63. C 28 H 34 N 6 0 6 requires C, 61.08; H, 6.22; N, 15.26. EXAMPLE 24 2, 6-Pi { 3 ' -hydroxypropoxy) -4 , 8-di [ (IV-benzylmethyl) - amino] pyrimidopyrimidine (NU3088 ) (a) 1st Stage - Preparation of 2 , 6-Pichloro-4 , 8-di [ { N- benzylmethyl) amino] pyrimidopyrimidine ZV-Benzylmethylamine (0.242g, 2mmol) was added to tetrachloropyrimidopyrimidine (0.135g, 0.5mmol) in THF (10ml) and stirred for 10 minutes until a yellow precipitate formed. Water (40ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in va cuo (P 2 Os) yielding the title compound as a yellow powder (0.159g, 72%), m.p. 191-192°C. (b) 2nd Stage - Preparation of 2 , 6-Di ( 3 ' -hydroxy- propoxy) -4, 8-di [ (IV-benzylmethyl) amino] pyrimidopyrimidine Sodium hydride (0.144g, 6mmol) was added to 1,2- propane diol (0.45ml, δmmol) in dry THF (5ml) and stirred for 10 hours at room temperature. To this was added 2,6- dichloro-4 , 8-di [ (IV-benzylmethyl) amino] pyrimidopyrimidine (0.132g, 03mmol) in dry THF (15ml) and the resulting mixture was heated under reflux for 96 hours. After cooling to room temperature, water (30ml) was added and the product extracted with ethyl acetate (4x20ml) . The combined extracts were dried (MgS0 4 ) and the solvent evaporated. Recrystallisation from methanol/water yielded the title compound as a cream fluffy solid (O.lOlg, 65%), m.p. 109-111°C. Found: C, 64.78; H, 6.81; N, 16.16. C 28 H 34 6 O 4 requires C, 64.85; H, 6.61; N, 16.20. EXAMPLE 25 2 , 6-Di (2 ' -hydroxyethoxy) -4 , 8-di ( 4 ' -methoxybenzylamino) - pyrimidopyrimidine (NU3089) Sodium hydride (0.24g, lOmmol) was added to ethylene glycol (0.62g, lOmmol) in dry THF (5ml) and stirred for 10 hours at room temperature. To this was added 2 , 6-Di (2 ' -hydroxyethoxy) -4 , 8-di ( 4 ' -methoxybenzyl- amino) pyrimidopyrimidine (see Example 17) (0.236g, 0.5mmol) in dry THF (15ml) and the resulting mixture was heated under reflux for 72 hours. After cooling to room temperature water (30ml) was added and the product extracted with ethyl acetate (4x20ml) . The combined extracts were dried (MgS0 4 ) and the solvent evaporated. Recrystallisation from iso-propanol yielded the title compound as an off-white powdery solid (0.048g, 18%), m.p. 189-191°C. Found: C, 59.71; H, 5.72; N, 15.89. C 26 H 3 oN 6 0 6 requi re s C , 5 9 . 7 6 ; H , 5 . 7 9 ; N , 1 6 . 08 . EXAMPLE 2 6 2 , 6-Di (3' -hydroxypropoxy) -4 , 8-di [ (V-4 ' -methoxybenzyl- methyl) amino] pyrimidopyrimidine (NU3090 ) (a) 1st Stage - Preparation of 2 , 6-Dichloro-4 , 8-di [ (_V- 4-methoxybenzylmethyl) amino] pyrimidopyrimdine IV-4-Methoxybenzylmethylamine (1.208g, δmmol) was added to tetrachloropyrimidopyrimidine (0.54g, 2mmol) in THF (30ml) and stirred for 10 minutes until a yellow precipitate formed. Water (80ml) was added and the mixture stirred for a further 10 minutes. The precipitate was filtered under suction, washed with water and dried in vacuo (P2O 5 ) yielding the title compound as a yellow powder (0.765g, 77%), m.p. 172-174°C. (b) 2nd Stage - Preparation of 2 , 6-Di { 3 ' -hydroxypropoxy) -4, 8-di [ (IV-4' -methoxybenzylmethyl) amino] - pyrimidopyrimidine Sodium hydride (0.096g, 4mmol) was added to 1,2- propane diol (0.304ml, 4mmol) in dry THF (5ml) and stirred for 10 hours at room temperature. 2 , 6-dichloro- 4 , δ-di [ (IV-4 ' -methoxybenzylmethyl) amino] pyrimidopyrimidine (0.20g, 0.4mmol) in dry THF (15ml) was added and the resulting mixture was heated under reflux for 96 hours. After cooling to room temperature, water (30ml) was added and the product extracted with ethyl acetate (4x20ml) . The combined extracts were dried (MgS0 4 ) and the solvent evaporated. Purification by column chromatography on silica gel with dichloromethane : methanol (95:5) as eluent and then recrystallisation from methanol/water yielded the title compound as a cream crystalline solid (0.044g, 19%), m.p. 125-127°C. Found: C, 61.67; H, 6.54; N, 14.16. C 3 oH 38 6 0 6 requires C, 61.69; H, 6.66; N, 14.39. EXAMPLE 27 2, 6-Di (n)propoxy-4, 8-di [ (N-benzylmethyl ) ammo] - pyrimidopyrimidine (NU3091) Propan-1-ol (0.30g, 5mmol) was dissolved in dry THF (5ml) and added to sodium hydride (0.12g, 5mmol) and stirred for 9 hours at room temperature. 2 , 6-dichloro- 4, 8-di [ (N-benzylmethyl) amino] pyrimidopyrimidine (see Example 24) (0.22g, 0.5mmol) in dry THF (10ml) was added to this and the mixture heated under reflux for 48 hours. After cooling to room temperature, water (30ml) was added and the product extracted into ethyl acetate (4x20ml) . The organic layers were combined, dried (MgS0 4 ), filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as white needles (0.103g, 40%), m.p. 119-120°C. Found: C, 69.05; H, 6.75; N, 17.12. C28H 3 4N 6 O2 requires C, 69.11; H, 7.04; N, 17.27%. EXAMPLE 28 2 , 6-Di { -2 ' -methoxyethoxy) -4 , 8-di [ (N-benzylmethyl) ammo] - pyrimidopyrimidine (NU3092) 2-Methoxyethanol (0.38g, 5mmol) was dissolved in dry THF (5ml) . The resulting solution was added to sodium hydride (0.12, 5mmol) and the mixture stirred for 9 hours at room temperature. 2 , 6-dichloro-4 , 8-di [ (N- benzylmethyl ) amino] pyrimidopyrimidine (0.22g, 0.5mmol) in dry THF (10ml) was added and the mixture heated under reflux for 48 hours. After cooling to room temperature, water (30ml) was added and the product extracted into ethyl acetate (4x20ml) . The organic layers were combined, dried (MgS04) , filtered and the solvent removed in va cuo . Recrystallisation from methanol/water yielded the title compound as white needles (0.103g, 40%), m.p. 116-118°C. Found: C, 64.89; H, 6.50; N, 16.24. C 28 H 34 N 6 θ 4 requires C, 64.85; H, 6.61; N, 16.20%. EXAMPLE 2 9 2 , 6-Di- (2-hydroxyethylamino) -4 , 8-dibenzylaminopyrimido- pyrimidine (NU3101) (a) 1 st Stage - Preparation of 4 , δ-dibenzylamino-2 , 6- dichloropyrimidopyrimidine Benzylamine (1.00 ml, 9.26 mmol) was added to a solution of 2 , 4 , 6, 8-tetrachloropyrimido-pyrimidine (0.50 g, 1.85 mmol) in dry THF (20 ml), containing K 2 C0 3 (1.40 g, 13.89 mmol), under a N 2 atmosphere. The reaction mixture was stirred at room temperature for 20 min, water (30 ml) was added and stirring was continued for a further 20 min. The resultant precipitate was collected by filtration, washed with water, and dried in va cuo to yield the named product (0.53 g, 70%) as a pale yellow solid. NMR data was as follows: δ H (200 MHz, CDC1 3 ) 4.73-4.76 (d, 4H, 2xArCH 2 NH, J=6Hz), 7.22-7.29 (t, 2H, 2xArCH 2 NH) , 7.33 (m, 10H, lOxAr-H) ; m/z (El) 410, 412, 414 (M + , 9:6:1 ratio, 31%), 270, 106, 91 (100%) . (b) 2 nd Stage - Preparation of 2, 6-Di- (2- hydroxyethylamino) -4 , 8-dibenzyIaminopyrimido- pyrimidine (NU3101) A mixture of 2 , 6-dichloro-4 , 8-di- (benzylamino) - pyrimidopyrimidine (0.32 g, 0.78 mmol) and ethanolamine (2 ml) was stirred at 150 °C for 12 h. The reaction mixture was cooled to room temperature and water (15 ml) was added, after which the mixture was stirred for a further 20 min, filtered, washed with water, and the collected solid dried in va cuo . Purification by silica column chromatography (dichloromethane : methanol, 9:1) yielded the title compound (0.11 g, 31%) as a fluorescent yellow solid (Found: C, 61.0; H, 6.0; N, 23.7. C 24 H 28 N 8 O 2 .0.14CH 2 Cl 2 requires C, 61.4; H, 5.6; N, 23.2); NMR data was as follows: V MAX (KBr/crrf 1 ) 3396, 3358, 3058, 2920, 747 and 715); δ H (200 MHz, d 6 -DMSO) 3.41-3.46 (m, 4H, 2xNHCH 2 CH 2 OH) , 3.55- 3.60 (m, 4H, 2xNHCH 2 CH 2 OH) , 4.65-4.68 (t, 2H, 2xOH, J=5Hz), 4.72-4.76(d, 4H, 2xPhCH 2 , J=6Hz), 6.07-6.13 (t, 2H, 2xNH, J=6Hz), 7.72-7.75 (t, 2H, 2xNH, J=6Hz); m/z (El) 460 (M + , 18%), 416 (M + -CH 2 CHO) , 91 (C 7 H 7 + , 100%), 69 (C 5 H 9 + ); δ c (200MHz, d 6 -DMSO) 43.42 (HOCH 2 CH 2 NH) , 44.07 (HOCH 2 CH 2 NH) , 60.64 (PhCH 2 NH), 127.02 (Ar-C-2), 127.63 (Ar-C-3), 127.89 (Ar-C-4/8), 128.57 (Pyr C-5), 140.22 (Ar-C-1), 156.44 (Pyr C-5), 158.35 (Pyr C-2/6) . Similarly prepared from 2 , 6-dichloro-4 , 8-di (benzylamino) pyrimidopyrimidine or 2 , 6-dichloro-4 , 8-di- (IV- methoxy-V-methylbenzylamino) pyrimidopyrimidine and either ethanolamine or diethanolamine were the following compounds: EXAMPLE 30 2 , 6-Di- (2-hydroxyethyl) amino-4 , 8-di- [4-methoxybenzyl] - aminopyrimidopyrimidine (NU3099) m.p. 161-163°C (Found C, 59.14; H, 6.30; N, 21.61. C 26 H 32 N 8 O 4 .0.25H 2 O requires C, 59.47, H, 6.24, N, 21.34. EXAMPLE 31 2 , 6-bis-Piethanolamino-4 , 8-di- (IV- [ 4 -methoxybenzyl] -N- methyl) aminopyrimidopyrimidine (NU3102) m.p. 190-192°C (Found C, 59.61; H, 6.99; N, 16.55. C 32 H 44 0 6 N 8 0.50EtOAc requires C, 59.14; H, 6.82; N, 17.24) . EXAMPLE 32 2, 6-Pi- (2-hydroxyethylamino) -4 , 8-di- [3, 4 -dimethoxybenzyl] aminopyrimidopyrimidine (NU3104 ) NMR data was as follows : δ H (200MHz, d 6 -PMSO) 3.43-3.51 (t, 4H, 2xNHCH 2 CH 2 OH, J=5.2Hz) , 3.57-3.92 (t, 4H, 2xNHCH 2 CH 2 OH, J=5.0Hz) , 3.82 3δ (s, 6H, 2xOCH 3 ) , 4.64-4.72 (m, 6H, 2xPhCH 2 and 2xOH) , 6.10-6.16 (t, 2H, 2xNH, J=5.4Hz), 6.9δ(s, 4H, 4xAr-H) , 7.13 (s, 2H, 2xAr-H) , 7.59 (t, 2H, 2xNH) . EXAMPLE 33 2 , 6-Pi- (3-hydroxypropoxy) -4 , 8-di- (IV- [4 -methoxybenzyl] -IV- methyl) aminopyrimidopyrimidine (NU3100) (a) 1 st Stage - Preparation of 3-Triisopropylsilyloxy- propan-1-ol To a stirred solution of imidazole (0.46 g, 6.92 mmol) and propane-1, 3-diol (5 ml, 69.16 mmol) in dry PMF (5 ml) was added triisopropylchlorosilane (1.46 ml, 6.92 mmol) dropwise. The reaction mixture was stirred at room temperature under N 2 for 36 h, and water (50 ml) was added. The mixture was extracted with ether (3 x 50 ml), and the organic layers were combined, washed with water (5 x 50 ml) and dried (Na 2 S0 4 ) . Evaporation of the solvents in va cuo gave the named product (1.38 g, 92%) as a colourless oil. NMR data was as follows: δ H (200 MHz, CPC1 3 ) 1.02-1.09 (m, 21H, 3x α Pr-H) , 1.75-1.83 (q, 2H, HOCH 2 CH 2 CH 2 ) , 2.15 (s, 1H, OH), 3.74-3.84 (m, 2H, HOCH 2 CH 2 CH 2 ) , 3.88-3.94 (t,2H, HOCH 2 CH 2 CH 2 ) . (b) 2 nd Stage - Preparation of 2 , 6-Di- (3-Tri- isopropylsilyloxypropoxy) -4 , 8-di- (IV- [4- methoxybenzyl] -IV-methyl) aminopyrimidopyrimidine Sodium hydride (0.15 g, 3.90 mmol) was added to a solution of 3-triisopropylsilyloxypropan-l-ol (0.84 g, 3.90 mmol) in dry THF (5 ml) under a N 2 atmosphere. The grey suspension was stirred at RT for 10 min, heated to 75 °C for 30 min, and then allowed to cool to ambient temperature. A solution of 2 , 6-Dichloro-4 , 8-di- (IV- [4- methoxybenzyl] -IV-methyl) aminopyrimidopyrimidine (0.39 g, 0.78 mmol) in dry THF (20 ml) was added, and the mixture was heated under reflux for 12 h. After cooling, water was added and the mixture was stirred for 20 min and extracted with ethyl acetate (5 x 30 ml) . The organic layers were combined, dried (NaS0 4 ), and the solvents were evaporated under reduced pressure to afford a yellow oil (0.47 g, 5.3mmol) . This compound was used in the next stage without further purification. (c) 3 rd Stage - Preparation of 2, 6-Di- (3- hydroxypropoxy) -4 , 8-di- (IV- [ 4 -methoxybenzyl] -IV- methyl) aminopyrimido-pyrimidine (NU3100) Tetrabutylammonium fluoride (1M solution in THF, 2.12 ml, 2.12 mmol, 4 mol . eq.)was added dropwise to a solution of 2 , 6-di- (3-triisopropylsilyloxypropoxy) -4 , 8- di- (IV- [ 4-methoxybenzyl] -IV-methyl) aminopyrimidopyrimidine (0.47 g, 0.53 mmol) in dry THF (10 ml) and the mixture was stirred at room temperature under a N 2 atmosphere for 1 h. Evaporation of solvents furnished a dark yellow oil which was dissolved in water (50 ml), and the aqueous solution was extracted with dichloromethane (4x20 ml) . The combined organic layer was dried (Na 2 S0 ) and solvents were removed in vacuo to give a brown oil. The title compound was isolated by chromatography on silica, employing dichloromethane: methanol (9:1) as eluent, as a pale yellow solid (0.18 g, 6%). The measured NMR data was as follows : δ H (200Mhz, d 6 -DMSO) 1.77-1.84 (t, 4H, 2xOCH 2 CH 2 CH 2 , J=6Hz) , 3.34 (s, 6H, 2xNCH 3 ) , 3.81 (s, 6H, 2xOCH 3 ) , 3.49-3.51 (t, 4H, 2xOCH 2 CH 2 CH 2 OH) , 4.13 (t, 4H, 2xOCH 2 CH 2 CH 2 OH) , 4.55- 4.60 (t, 2H, 2xOH, J=5Hz) , 5.50 (br s, 4H, 2xMeOPhCH 2 ) , 6.96-7.00 (d, 4H, ArH-3, H-5, J=9Hz) , 7.27-7.31 (d, 4H, ArH-2, H-6, J=9Hz) ,; m/z (El) 578 (M + , 44%) , 457 (M + - MeOC 7 H 7 ) , 150 (MeOC 7 H 7 NMe + ) , 121 (MeOC 7 H 7 + ) . Similarly prepared from 2 , 6-dichloro-4 , 8- (N-methyl- benzylamino) pyrimidopyrimidine and 2-triisopropyl- silyloxyethanol was the following: EXAMPLE 34 2, 6-Pi- (2-hydroxyethoxy) -4 , 8-di- (V-benzyl-IV-methyl) aminopyrimidopyrimidine (NU3103) The measured NMR data was as follows : δ H (200MHz, CPC1 3 ) 1.64 (br s, 1H, OH), 1.98 (br s, 4H, 4xOH) , 3.23 (s, 6H, 2xNCH 3 ) , 3.62-3.64 (t, 4H, 2xHOCH 2 CH 2 0, J=4.5Hz), 3.89-3.94 (t, 4H,, 2xHOCH 2 CH 2 0, J=4.4Hz), 5.41 (s, 4H, 2xPhCH 2 ), 7.16-7.30 (m, 10H, lOxAr- H) ; m/z (El): 490 (M + , 64%), 475 (M + -CH 3 ) , 399 (M + -C 7 H 7 ), 91(C 7 H 7 + , 100%), 69 (C 5 H 9 + ) . BIOLOGICAL ACTIVITY In vi tro activity. Tables 1 and 2 at the end of the present description show in vi tro test results obtained in various sets of experiments in which the inhibition of thymidine uptake into L1210 cells (murine leukaemia cell line) grown in culture, both in the absence of and in the presence of AGP was measured for a range of selected compounds of the present invention. Nucleoside Transport Inhibition Assays For testing the compounds an established nucleoside transport assay involving measurement of thymidine uptake was adapted. Murine leukaemia L1210 cells were used in this assay as their nucleoside transport characteristics are well known. This assay for measuring thymidine uptake used a modification of the rapid mixing technique of Wohleheuter, R.M. et al (1978) Methods in Cell Biology 20 211-236. The uptake of lOOμM thymidine by 10 6 cells was followed at 2 second intervals over a 12 second time course in the presence or absence of inhibitor in 1% or 5% DMSO. In some experiments uptake was also measured in the presence of 5mg/ml human oti acid glycoprotein (AGP) . This represents the upper limit of concentration of patient plasma AGP and is approximately 125μM (M.W. approximately 40,000 Da) i.e. > lOx molar excess of inhibitor tested at lOμM. Materials used included a transport buffer comprising 130mM NaCl, 5mM KC1, ImM MgCl, 5mM NaH 2 P0 4 , lOmM glucose and lO M HEPES. This buffer was made up as sterile 5x concentrate and reconstituted in distilled water and adjusted to pH 7.4 immediately prior to carrying out the assay. The L1210 cells were generally prepared as follows: 300ml of L1210 cells in exponential growth phase (< δxlO 5 cells/ml) grown in RPMI 1640 medium supplemented with 10% foetal calf serum were centrifuged at lOOOrpm for 5 minutes at 4°C. The supernatant was aspirated and the cells were washed with ice-cold transport buffer and centrifuged again at lOOOrpm for 5 minutes at 4°C. The supernatant was removed and the cells were resuspended in ice-cold transport buffer to give a final cell density of 2-4xl0 7 cells/ml. Cells were left on ice for 30 minutes recovery prior to starting the assay. In a typical procedure for carrying out the thymidine uptake transport assay, 333μl of cell suspension and 323μl transport buffer (± 15.46mg/ml AGP) were incubated with lOμl inhibitor (dissolved in DMSO at lOOx the desired final concentration) or lOμl DMSO (control) for at least 5 minutes at 21°C. For less soluble compounds the DMSO concentration was increased, in which case 333μl cells and 2δ3μl (± 17.65mg/ml AGP) transport buffer were incubated with 50μl of inhibitor (at 20x the desired final concentration) or 50μl DMSO. The suspension was mixed well and lOOμl was layered onto 150μl silicone oil (9:11 Dow Corning 556 (Sp.Gr. 0.9δ):Dow Corning 550 (Sp.Gr. 1.066) (final Sp . Gr . 1.026) overlaying 50μl 3M KOH m 6 replicate 0.5ml microfuge tubes. Transport was initiated by adding 50μl of 300μM thymidine m transport buffer labelled with 25μCι/ml [methyl- 3 H] thymidine and 2μCι/ml [ 14 C] sucrose to each tube m turn at one second intervals in time to a metronome set at 60 beats/mmute using an Eppendorf multipette with a 1.25ml tip. Following a wait beat, transport was stopped by the addition of 50μ of 400μM dipyridamole m transport buffer (acidified with HC1) at one second intervals to the tubes m reverse order. The tubes were immediately transferred to a microfuge (Eppendorf) and spun at 12000 rpm for 2 minutes to pellet the cells through the oil and into the KOH. The tubes were capped and the cells left to solubilise in the KOH for 1 hour. Cell number and viability for each run was determined by haemocytometer counting using trypan blue exclusion. At least two positive control incubations lμM or lOμM dipyridamole were included in each experiment. The tubes were capped and cut m the oil layer such that the bottom portion (cells solubilised in KOH) fell into a 20ml scintillation vial. 1ml 0.25M acetic acid followed by 1ml air was injected into the tube using a 2ml syringe and 23-gauge needle to disperse and neutralise the KOH- solubilised cells. 10ml of Optiphase HiSafe™ scintillant was added and the vials capped and shaken. Triplicate lOμl aliquots of the 300μM thymidine + 25μCι/ml [methyl- 3 H] thymidine and 2μCι/ml [ 14 C] sucrose were also counted as standards. The [ 14 C] : [ 3 H] ratio was used to calculate the amount of non-transported contaminating [ 3 H]thymιdιne m the extracellular space. The accumulation of [ 3 H] thymidine was calculated as pmol/10 6 viable cells. The rate of thymidine uptake in the presence and absence of inhibitor was calculated from linear regression of pmol thymιdme/10 6 cells vs time (in seconds) using GraphPad PRIZM™ software and comparison of rates m the presence of inhibitor with rate in the absence of inhibitor gave the % inhibition of uptake. The results of these assays are given in Table 1 which is a full tabulated list of compounds that have been made including NU reference numbers, structures and membrane transport inhibition data with results in some cases obtained in different experiments for different concentrations of the compounds. Further data for selected compounds tested for inhibition of nucleoside transport at 1 and lOμM concentration in the presence of 5mg/ml AGP are given in Table 2. It will be seen that lOμM dipyridamole inhibited thymidine uptake by approximately 100% in the absence of AGP but this was virtually abolished in the presence of AGP. The effect of AGP on the inhibition of thymidine uptake by other analogues was significantly less than for dipyridamole and in the case of NU3076, NU3077, NU30δ4 and NU3087, for example, there was no significant reduction of inhibition by AGP. Moreover, NU3076 and NU3084 at least appear to be more potent inhibitors than dipyridamole both in the presence and absence of AGP or, as found in other assays, in the presence or absence of 40mg/ml human serum albumin. Growth Inhibition Assays In addition to identifying compounds that inhibit nucleoside transport some have also been tested for their ability to inhibit thymidine rescue of thymidylate synthase-inhibited cells, using L1210 cells again and the antifolate drug known as CB3717. The antifolate, CB3717, inhibits cell growth by inhibiting thymidylate synthase (TS) which is responsible for the conversion of dUMP to dTMP that is later phosphorylated to dTTP for DNA synthesis. Inhibition of TS results in the depletion of intracellular dTTP and, because of an increase of dUMP behind the block, an increase in dUTP which causes DNA strand breakage (see Curtin et al , Cancer Research , 51 2346-2353, 1991) . Salvage of extracellular thymidine through nucleoside transport and thymidine kmase activity can provide the necessary dTMP and hence rescue the cell. Inhibition of nucleoside transport potentiates the activity of TS inhibitors by preventing the efflux of deoxyuπdme, leading to a greater accumulation of dUTP and by preventing rescue by the uptake of exogenous thymidine. In carrying out these growth inhibition assays, L1210 cells were adapted to growth in RPMI 1640 medium supplemented with 10% dialysed serum (dialysed for 24 hours at 4°C against 2 changes of 9 volumes of PBS containing lg activated charcoal/L and a further 2 changes of 9 volumes of PBS) . All experiments were performed using medium supplemented with dialysed serum to remove exogenous nucleosides. Cells in log phase growth were suspended at 4xl0 4 cells/ml, and solutions of CB3717, thymidine and inhibitor were prepared at 4x the final desired concentration in RPMI 1640 + 10% dialysed serum. Concentrated stocks of the inhibitors were dissolved DMSO, the DMSO concentration was controlled so as to be present at 0.1% m the final incubation except where indicated. 0.25ml cell suspension, 0.25ml medium ± CB3717, 0.25ml medium ± thymidine and 0.25ml medium ± inhibitor were dispensed into each well of a 24 well plate (4-6 replicate wells/drug contamination) . Replicate 0.25ml aliquots of the remaining cell suspension were counted to obtain a time 0 cell count. After incubation at 37°C for 48 hours (to allow for a minimum of 3 cell doublings) cells were enumerated using a Coulter counter Model Zl. The results of these assays in which the growth inhibition of L1210 cells by CB3717 was measured m the presence and absence of inhibitor (concentration 0, 1 and lOμM) , and with and without lμM thymidine, showed that all the inhibitors increased the growth inhibition by CB3717 and could block to a varying extent the thymidine rescue. Thus, it was demonstrated that enhancement of thymidylate synthase inhibitor cytotoxicity and prevention of thymidine rescue, as evidenced by potentiation of CB3717 growth inhibition, is related to the extent and potency of nucleoside transport inhibition produced by the dipyridamole analogue concerned. In general, the studies carried out fully support the belief that the nucleoside transport inhibitory characteristics of the compounds tested reflect an ability of these compounds to potentiate the cytotoxicity of antimetabolite agents, such as certain cytotoxic antitumour drugs used in cancer therapy. Accordingly, having regard to their significant nucleoside transport inhibitory characteristics and reduced binding affinity for AGP (as compared to dipyridamole) , the compounds of this invention can be expected to be especially useful in vivo for administration in conjunction with such cytotoxic drugs in order to potentiate the cytotoxic effect of the latter in the course of medical treatment, as hereinbefore indicated. As mentioned earlier in this specification further information and data obtained from recent work investigating inhibition of purine uptake, particularly hypoxanthine, by dipyridamole and the effect of this in relation to selective potentiation of cytotoxic antifolate agents has now been published in the documents referred to. Although the newly published data relates particularly to dipyridamole, tests carried out on dipyridamole analogues disclosed herein, especially compound NU3076, have shown a behaviour similar to dipyridamole, at least in respect of preventing hypoxanthine rescue from LY309887 (an analogue of the antifolate drug lometrexol) growth inhibition for selected tumour cell lines. For example, in investigating the compound NU3076, two lung cancer cell lines: A549 and COR L23 and two breast cancer cell lines MCF7 and MDA MB231 were selected for study. All cell lines were adapted to growth in dialysed serum as previously referred to. In earlier experiments, it had been shown that dipyridamole blocked hypoxantine rescue from lometrexol growth inhibition in A549 and MCF7 but not in COR L23 and MDA MB231. In these further investigations, all cell lines were seeded into 96-well plates and drug incubation periods were between 72 and 144 hours depending on the growth rate of the cell under study, sufficient to ensure that control cultures had undergone at least 3 cell doublings. Cells were exposed to varying concentrations of LY309887 in the presence or absence of lOμM hypoxanthine, with or without 3μM NU3076. At the end of the exposure period the cells were fixed and stained with sulphorhodamineB . Hypoxanthine protected all the cell lines from LY309887 growth inhibition. NU3076 prevented hypoxanthine rescue in A549 and MCF7 cells but not COR L23 and MDA MB231. Thus, the cells displayed the same differential sensitivity to NU3076 as they do to dipyridamole, but most importantly the results have again demonstrated the therapeutic potential of certain dipyridamole analogues, again emphasising the desirability of enlarging the available range of such compounds . As will be seen, overall the invention provides a number of different aspects and it embraces each and every novel and inventive feature and aspect herein disclosed, either explicitly or implicitly and either singly or in combination with one another. Moreover, the scope of the invention is not to be construed as being limited by the illustrative examples or by the terms and expressions used herein merely in a descriptive or explanatory sense. TABLE 1 TABLE 1 (contd). TABLE 1 (contd. TABLE 1 (contd.) TABLE 1 (contd.) TABLE 1 (contd.) TABLE 1 (contd. TABLE 1 (contd.) TABLE 2 TABLE 2 (contd.)

Claims: CLAIMS 1. A pyrimidopyrimidine compound which is a compound having the general structural formula I or a pharmaceutically acceptable salt thereof, characterised in that in structural formula I Ri is chloro and R 3 is diethanolamino, or Ri and R 3 are identical and are selected from allyl, halo, diethanolamino, solketalo and a group having the formula -0-R z or -NHR Z , R z being selected from alkyl, hydroxyalkyl, alkoxyalkyl, dialkoxyalkyl and 2-oxo-alkyl wherein the or each alkyl and/or alkoxy moiety has less than six carbon atoms, and R 2 and R are identical and are selected from piperidino, N-tetrahydroisoquinolyl, and a benzylamino group having the structural formula II where R 5 is H, or an optionally substituted alkyl or benzyl group, and R 6 and R7 represent H or optional substituents in the aromatic nucleus selected from halo, alkyl, alkoxy, hydroxy, trifluoromethyl, azido, cyano, nitro, carboxyl, carboxylic ester, ammo or a substituted ammo NR x R y where R x and R y each represent hydrogen or alkyl, subject to the provisos that (a) if Ri and R 3 are both chloro or diethanolamino, R 2 and R 4 are not both benzylamino, i.e. R 2 and R 4 do not correspond to structure II with R 5 , R 6 and R 7 each being hydrogen, and (b) if R and R 4 are both piperidino, Ri and R 3 are not both chloro, diethanolamino, solketalo or (2 , 3-dιmethoxy) propoxy; said compound being further characterised by an ability selectivity to inhibit transport of nucleosides or purmes across membranes of at least certain cell types m biological cellular systems . 2. A pyrimidopyrimidine compound according to Claim 1 wherein all alkyl groups when present as such, or as a moiety m other groups such as alkoxy, are lower alkyl groups containing 1-5 carbon atoms. 3. A pyrimidopyrimidine as claimed m Claim 1 or 2, wherein R 2 and R are piperidino, and Ri and R 3 are each selected from allyl, methoxy, ethoxy, n-propoxy, ISO- propoxy, iso-butoxy, 3-methylbutoxy, 2-oxo-n-propoxy, 2 , 2-dιethoxy-n-propoxy, (2-methoxy-l-methyl) ethoxy, 2- methoxyethoxy, 2-hydroxypropoxy, 2-hydroxyethoxy and 3- hydroxypropoxy . 4. A pyrimidopyrimidine as claimed in Claim 1 or 2, wherein R 2 and R 4 are N-tetrahydroisoquinolyl and Ri and R 3 are each selected from diethanolamino and chloro. 5. A pyrimidopyrimidine as claimed in Claim 1 or 2, wherein R 2 and R are each a benzylamino group of structural formulae II and R_ and R 3 are selected from 2- methoxyethoxy, propoxy, 2-hydroxypropoxy, diethanolamino, solketalo, chloro, 2-hydroxyethoxy and 3-hydroxypropoxy . 6. A pyrimidopyrimidine as claimed in Claim 1 or 2, wherein R 2 and R 4 are each a benzylamino group of formula II in which at least one of R 6 and R^ is alkoxy. 7. A pyrimidopyrimidine as claimed in Claim 6, wherein R 6 is selected from 4-methoxy and 3-methoxy substituents. 8. A pyrimidopyrimidine as claimed in Claim 6 or 7 , wherein R 5 is methyl. 9. A pyrimidopyrimidine as claimed in Claim 1 or 2 wherein R 2 and R are each a benzylamino group conforming to structural formulae II in which the combination of substituents R 5 , Re and R 7 is selected from the following combinations : R 5 R 6 R7 H 4-OMe H Me 4-OMe H H 4-OMe 3-OMe Me 4-OMe 3-OMe H H H Me H H benzyl H H H 4-CF 3 H 10. A pyrimidopyrimidine compound which is one of the following : 2, 6-di- (3-hydroxypropoxy) -4, 8-di- (IV 4-methoxy- benzyl-I -methylamino) pyrimidopyrimidine; 2 , 6-bis-diethanolamino-4 , 8-di- ( 4-methoxybenzyl- amino) pyrimidopyrimidine; 2 , 6-bis-diethanolamino-4 , 8-bis- (3, 4-dimethoxy- benzylamino) pyrimidopyrimidine; 2, 6-di- (2-hydroxypropoxy) -4, 8-di- (4-methoxybenzyl- amino) pyrimidopyrimidine; 2, 6-di (-3-hydroxypropoxy) -4, 8-di (-4-methoxy- benzylamino) pyrimidopyrimidine; 2, 6-di- (2-hydroxyethoxy) -4, 8-di- (IV-4-methoxy- benzyl-V-methylamino) pyrimidopyrimidine; 2 -chloro- 6-diethanolamino- 4 , 8-bis [ (3, 4 -dimethoxybenzyl) amino] pyrimidopyrimidine; 2, 6-di (-3 -hydroxypropoxy) -4 , 8-bis [ (-3, 4 -dimethoxybenzyl ) -N-methylamino] pyrimidopyrimidine; 2, 6-bis (diethanolamino) -4, 8-di ( 4-chlorobenzyl- amino ) pyrimidopyrimidine ; 2, 6-di- (3-hydroxypropoxy) -4 , 8-di- (IV-benzylmethyl- amino ) pyrimidopyrimidine ; 2, 6-di (-2 -hydroxyethoxy) -4, 8-di ( IV-methyl - benzylamino) pyrimidopyrimidine; 2, 6-di (-2-methoxyethoxy) -4, 8-dibenzylamino- pyrimidopyrimidine ; 2, 6-di- (2-methoxyethoxy) -4, 8-di- (IV-benzyl-IV-methyl- amino) pyrimidopyrimidine; 2, 6-disolketalo-4 , 8-dibenzylaminopyrimido- pyrimidine; 2, 6-bis-diethanolamino-4 , 8-di- ( 4-trifluoromethyl- benzylamino) pyrimidopyrimidine; 2 , 6-di (-2 -methoxyethoxy) -4 , 8-bis (dibenzylamino) pyrimidopyrimidine; 2 , 6-dipropoxy-4 , 8-di- ( V-benzyl-IV-methylamino) - pyrimidopyrimidine ; 2 , 6-di (-2-hydroxyethyl) amino- 4 , 8-di ( 4 - methoxybenzyl ) aminopyrimidopyrimidine 2 , 6-di (-2-hydroxyethylamino) -4, 8-dibenzyl- aminopyrimidopyrimidine 2, 6-bis -diethanolamino- 4, 8-di- ( -methyl-V- [4- methoxybenzyl] ) aminopyrimidopyrimidine 2 , 6-di- (2-hydroxyethyl ) amino- 4 , 8-bis- (3, 4- dimethoxybenzyl) aminopyrimidopyrimidine 2, 6-Di- (3 -hydroxypropoxy) -4, 8-di-(IV- [4- methoxybenzyl] -IV-methyl) aminopyrimidopyrimidine 2, 6-Di- (2 -hydroxyethoxy) -4, 8-di- (IV-benzyl -IV- methyl) aminopyrimidopyrimidine (2 -hydroxypropoxy) -4, 8-dipiperidino- pyrimidopyrimidine ; (3-hydroxypropoxy) -4, 8-dipiperidino- pyrimidopyrimidine ; (2-methoxyethoxy) -4, 8-dipiperidino- pyrimidopyrimidine ; (2-hydroxyethoxy) -4, 8-dipiperidino- pyrimidopyrimidine ; 2 , 6-bis [2 , 2 -diethoxy] -n-propoxy-4 , 8-dipiperidino- pyrimidopyrimidine; 2 , 6-di [2-oxo] -n-propoxy-4, 8-dipiperidino- pyrimidopyrimidine ; 2, 6-dimethoxy-4 , 8-dipiperidinopyrimidopyrimidine; 2 , 6-diethoxy-4 , 8-dipiperidinopyrimidopyrimidine; 2 , 6-di-3-methylbutoxy- , 8-dipiperidino- pyrimidopyrimidine ; (2-methoxy-l-methyl) ethoxy- 4 , 8-dipiperidino- pyrimidopyrimidine ; 2, 6-diallyl-4, 8 -dipiperidinopyrimidopyrimidine; 2 , 6-di-n-propoxy-4 , 8 -dipiperidinopyrimido- pyrimidine; 2 , 6-di-iso-propoxy-4 , 8 -dipiperidinopyrimi do- pyrimidine; 2 , 6-di-iso-butoxy-4 , 8 -dipiperidinopyrimido- pyrimidine. 11. A pyrimidopyrimidine compound as claimed in any of the preceding claims for use as an active therapeutic substance, characterised in that it is in the form of an acid addition salt derived from an acid selected from the group comprising: hydrochloric, hydrobromic, sulphuric, nitric, phosphoric, maleic, salicylic, p-toluenesulphonic, tartaric, citric, lactobionic, formic, malonic, pantothenic, succinic, naphthalene-2-sulphonic, benzenesulphonic, methanesulphonic and ethane- sulphonic . 12. A pyrimidopyrimidine compound as claimed in any one of the preceding claims for therapeutic use as an active inhibitor of cell membrane transport of nucleosides or purines in the course of therapeutic treatment of a mammal . 13. Use of a pyrimidopyrimidine compound as claimed in any one of the Claims 1 to 11 for the manufacture of a medical preparation for use in therapeutic treatment of a mammal . 14. A pharmaceutical formulation or composition containing a pyrimidopyrimidine compound as claimed in Claim 12 made up in unit dosage form for administration to a mammal likely to benefit from treatment with a cell membrane nucleoside or purine transport-inhibiting agent in the course of therapy. 15. A pharmaceutical formulation or composition for medical use comprising an effective cell membrane nucleoside or purine transport-inhibiting amount of a pyrimidopyrimidine compound as claimed in any one of Claims 1 to 12 admixed with a pharmaceutically acceptable carrier, diluent or excipient. 16. A pharmaceutical formulation or composition as claimed in Claim 14 or 15 for use in conjunction with cytotoxic agents in antitumour treatment. 17. A pharmaceutical composition containing an effective amount of a pyrimidopyrimidine compound as claimed in Claim 12 in admixture with a therapeutically useful and effective amount of a cytotoxic drug for use in antitumour treatment. 18. A pharmaceutical composition for selective use in conjunction with a cytotoxic drug in antitumour therapy, said composition containing as an active nucleoside transport inhibiting substance a pyrimidopyrimidine compound as claimed in any of Claims 1 to 11. 19. A pharmaceutical composition for selective use in conjunction with a cytotoxic antifolate drug in antitumour therapy, said composition containing as an active nucleoside transport inhibiting substance a pyrimidopyrimidine compound as claimed in any of Claims 1 to 11 in admixture with a pharmaceutically acceptable carrier, diluent or excipient. 20. Use of a pyrimidopyrimidine compound for the manufacture of a medical preparation for use in therapy for inhibiting membrane nucleoside or purine transport, such transport inhibition constituting an element of a therapeutic treatment, said compound providing the active transport inhibiting agent and being a pyrimidopyrimidine having the general formula I characterised in that in structural formula I Ri is chloro and R 3 is diethanolamino, or Ri and R 3 are identical and are selected from allyl, halo, diethanolamino, solketalo and a group having the formula -0-R z or -NHR Z , R z being selected from alkyl, hydroxyalkyl, alkoxyalkyl, dialkoxyalkyl and 2-oxo-alkyl wherein the or each alkyl and/or alkoxy moiety has less than six carbon atoms, and R 2 and R are identical and are selected from piperidino, N-tetrahydroisoquinolyl, and a benzylamino group having the structural formula II where R 5 is H, or an optionally substituted alkyl or benzyl group, and R 6 and R 7 represent H or optional substituents in the aromatic nucleus selected from halo, alkyl, alkoxy, hydroxy, trifluoromethyl , azido, cyano, nitro, carboxyl, carboxylic ester, amino or a substituted amino NR x R y where R x and R y each represent hydrogen or alkyl, subject to the provisos that (a) if Ri and R 3 are both chloro or diethanolamino, R 2 and R are not both benzylamino, i.e. R 2 and R 4 do not correspond to structure II with R 5 , R 6 and R 7 each being hydrogen, and (b) if R 2 and R 4 are both piperidino, Ri and R 3 are not both chloro, diethanolamino, solketalo or (2 , 3-dimethoxy) propoxy. 21. A method of therapeutic treatment carried out on a mammal wherein inhibition of nucleoside or purine cell membrane transport is considered likely to be beneficial, said method comprising administering to said mammal an effective nucleoside or purine membrane transport- inhibiting amount of a compound as claimed in any one of Claims 1 to 12. 22. A method as claimed in Claim 20 carried out in conjunction with administration of an antifolate cytotoxic drug in the course of antitumour therapy.

Inventors: CALVERT ALAN HILARY, CURTIN NICOLA JANE, GOLDING BERNARD THOMAS, GRIFFIN ROGER JOHN, NEWELL DAVID RICHARD, CALVERT, ALAN, HILARY, CURTIN, NICOLA, JANE, GOLDING, BERNARD, THOMAS, GRIFFIN, ROGER, JOHN, NEWELL, DAVID, RICHARD
Applicants: CALVERT ALAN HILARY, CURTIN NICOLA JANE, GOLDING BERNARD THOMAS, GRIFFIN ROGER JOHN, NEWELL DAVID RICHARD, UNIV NEWCASTLE VENTURES LTD, CALVERT, ALAN, HILARY, CURTIN, NICOLA, JANE, GOLDING, BERNARD, THOMAS, GRIFFIN, ROGER, JOHN, NEWCASTLE UNIVERSITY VENTURES LIMITED, NEWELL, DAVID, RICHARD
Application year: 1998
Main classification: C07D487
IPC codes: A61K31, A61P35, A61P43, C07D487