Abstract:
The present invention relates to compounds of the general formula (I) which are inhibitors of purine nucleoside phosphorylases (PNP), purine phosphoribosyltransferases (PPRT), 5′-methylthioadenosine phosphorylases (MTAP), 5′-methylthioadenosine nucleosidases (MTAN) and/or nucleoside hydrolases (NH). The invention also relates to the use of these compounds in the treatment of diseases and infections including cancer, bacterial infections, protozoal infections, and T-cell mediated disease and to pharmaceutical compositions containing the compounds.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates generally to certain nucleoside analogues, the use of these compounds as pharmaceuticals, pharmaceutical compositions containing the compounds, processes for preparing the compounds, and methods of treating diseases or conditions in which it is desirable to inhibit purine phosphoribosyltransferase, purine nucleoside phosphorylase, 5′-methylthioadenosine phosphorylase, 5′-methylthioadenosine nucleosidase and/or nucleoside hydrolase. 
       BACKGROUND 
       [0002]    U.S. Pat. No. 5,985,848, U.S. Pat. No. 6,066,722 and U.S. Pat. No. 6,228,741 describe nucleoside analogues that are inhibitors of purine nucleoside phosphorylase (PNP) and purine phosphoribosyl-transferases (PPRT). The analogues are useful in treating parasitic infections, T-cell malignancies, autoimmune diseases and inflammatory disorders. The analogues are also useful for immunosuppression in organ transplantation. 
         [0003]    PCT/NZ00/00048 describes a process for preparing certain PNP inhibitor compounds. This application recognises the compounds as PNP inhibitors and addresses a need for simpler methods of preparing them. PCT/NZ01/00174 discloses further nucleoside analogues that are inhibitors of PNP and PPRT. 
         [0004]    Certain nucleoside analogues have also been identified as potent inhibitors of 5′-methylthioadenosine phosphorylase (MTAP) and 5′-methylthioadenosine nucleosidase (MTAN). These are the subject of PCT/NZ03/00050. 
         [0005]    PNP catalyses the phosphorolytic cleavage of ribo- and deoxyribonucleosides, for example those of guanine and hypoxanthine, to give the corresponding sugar-1-phosphate and guanine, hypoxanthine or other purine bases. 
         [0006]    Humans deficient in purine nucleoside phosphorylase (PNP) suffer a specific T-cell immunodeficiency due to an accumulation of dGTP which prevents proliferation of stimulated T lymphocytes. Inhibitors against PNP are therefore immunosuppressive, and are active against T-cell malignancies and T-cell proliferative disorders. 
         [0007]    Nucleoside hydrolases (NH) catalyse the hydrolysis of nucleosides. These enzymes are not found in mammals but are required for nucleoside salvage in some protozoan parasites. Some protozoan parasites use nucleoside phosphorylases either instead of or in addition to nucleoside hydrolases for this purpose. Inhibitors of nucleoside hydrolases and phosphorylases can be expected to interfere with the metabolism of the parasite and can therefore be usefully employed against protozoan parasites. 
         [0008]    MTAP and MTAN function in the polyamine biosynthesis pathway, in purine salvage in mammals, and in the quorum sensing pathways in bacteria. MTAP catalyses the reversible phosphorolysis of 5′-methylthioadenosine (MTA) to adenine and 5-methylthio-α-D-ribose-1-phosphate (MTR-1P). MTAN catalyses the reversible hydrolysis of MTA to adenine and 5-methylthio-α-D-ribose and of S-adenosyl-L-homocysteine (SAH) to adenine and S-ribosyl-homocysteine (SRH). The adenine formed is subsequently recycled and converted into nucleotides. Essentially, the only source of free adenine in the human cell is a result of the action of these enzymes. The MTR-1P is subsequently converted into methionine by successive enzymatic actions. 
         [0009]    MTA is a by-product of the reaction involving the transfer of an aminopropyl group from decarboxylated S-adenosylmethionine to putrescine during the formation of spermidine. The reaction is catalyzed by spermidine synthase. The spermidine synthase is very sensitive to product inhibition by accumulation of MTA. Therefore, inhibition of MTAP or MTAN severely limits the polyamine biosynthesis and the salvage pathway for adenine in the cells. Likewise, MTA is the by-product of the bacterial synthesis of acylated homoserine lactones from S-adenosylmethionine (SAM) and acyl-acyl carrier proteins in which the subsequent lactonization causes release of MTA and the acylated homoserine lactone. The acylated homoserine lactone is a bacterial quorum sensing molecule in bacteria that is involved in bacterial virulence against human tissues. Recent work has identified a second communication system (autoinducer 2, AI-2) that is common to both Gram-positive and Gram-negative bacteria and thus has been proposed as a “universal signal” which functions in interspecies cell-to-cell communication. Again, MTAN generates S-ribosyl-homocysteine (SRH) that is the precursor of AI-2. Inhibition of MTAN or MTAP in microbes will prevent MTA removal and subject the pathway to product inhibition, thereby decreasing production of the quorum sensing pathway and decreasing the virulence of microbial infections. Inhibition of MTAN in microbes will prevent the formation of SRH, decreasing the production of the second quorum sensing pathway. 
         [0010]    MTAP deficiency due to a genetic deletion has been reported with many malignancies. The loss of MTAP enzyme function in these cells is known to be due to homozygous deletions on chromosome 9 of the closely linked MTAP and p16/MTS1 tumour suppressor gene. As absence of p16/MTS1 is probably responsible for the tumour, the lack of MTAP activity is a consequence of the genetic deletion and is not causative for the cancer. However, the absence of MTAP alters the purine metabolism in these cells so that they are mainly dependent on the de novo pathway for their supply of purines. That makes these cells unusually sensitive to inhibitors like methotrexate, alanosine and azaserine, that block the de novo pathway. Therefore, a combination therapy of methotrexate, alanosine or azaserine with an MTAP inhibitor will have unusually effective anti-tumour properties. 
         [0011]    MTAP inhibitors would also be very effective against parasitic infection such as malaria that infects red blood cells (RBCs), as they lack the de novo pathway for purine biosynthesis. Protozoan parasites depend entirely upon the purines produced by the salvage pathway for their growth and propagation. MTAP inhibitors will therefore kill these parasites without having any negative effect on the host RBCs, as RBCs are terminally differentiated cells and they do not synthesize purines, produce polyamines or multiply. 
         [0012]    The imino sugar part of the compounds described in the patent specifications referred to above has the nitrogen atom located between C-1 and C-4 so as to form 1,4-dideoxy-1,4-imino-D-ribitol compounds. The location of the nitrogen atom in the ribitol ring may be critical for binding to enzymes. In addition, the location of the link between the sugar moiety and the nucleoside base analogue may be critical for enzyme inhibitory activity. The compounds described above have that link at C-1 of the sugar ring. 
         [0013]    The applicants have also developed other nucleoside phosphorylase and nucleosidase inhibitors, where the location of the nitrogen atom in the sugar ring is varied and, additionally, where two nitrogen atoms form part of the sugar ring. Alternative modes of linking the sugar part and the base analogue have also been investigated, resulting in a class of inhibitors where the sugar moiety is linked to the nucleoside base analogue via a methylene bridge. These other inhibitors are described in PCT/NZ03/00186. 
         [0014]    However, there remains an ongoing need for new inhibitors of PNP, PPRT, MTAP, MTAN, and NH. In particular, the applicants have now found that ethylene-linked analogues of the abovementioned methylene-linked compounds are surprisingly potent inhibitors of PNP. The same class of compounds are anticipated to be inhibitors of PPRT, MTAP, MTAN, and NH. 
         [0015]    It is therefore an object of the present invention to provide compounds that are inhibitors of PNP, PPRT, MTAP, MTAN, and/or NH, or to at least provide a useful choice. 
       STATEMENTS OF INVENTION 
       [0016]    Accordingly, in a first aspect, the present invention provides a compound of the formula (I): 
         [0000]    
       
                 
         
             
             
         
       
       
         
           
             where:
           A is N or CH;   B is OH or NH 2 ;   D is H, OH, NH 2  or SCH 3 ; and   Z is OH or SQ, where Q is an optionally substituted alkyl, aralkyl, or aryl group;   
         
             or a tautomer thereof; or a pharmaceutically acceptable salt thereof; or an ester prodrug form thereof. 
           
         
       
     
         [0023]    Preferably A is CH. Alternatively, A may be N. 
         [0024]    It is also preferred that B is OH. Alternatively, B is NH 2 . 
         [0025]    It is further preferred that D is H. Alternatively, D may preferably be NH 2 , OH, or SCH 3 . 
         [0026]    In some preferred compounds of the invention Z is OH. In other preferred compounds Z is SQ. 
         [0027]    Further preferred compounds of the invention are those where Z is OH, A is CH, B is OH, and D is H or NH 2 . 
         [0028]    Other preferred compounds of the invention are those where Z is SQ, A is CH, B is NH 2 , and D is H. 
         [0029]    Preferred compounds of the invention include:
   (i) (3S,4S)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (ii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (iii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(ethylthiomethyl)-pyrrolidine;   (iv) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(2-fluoroethylthiomethyl)-pyrrolidine;   (v) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(2-hydroxyethylthiomethyl)-pyrrolidine;   (vi) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(propylthiomethyl)-pyrrolidine;   (vii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(isopropylthiomethyl)-pyrrolidine;   (viii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(butylthiomethyl)-pyrrolidine;   (ix) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(cyclohexylylthiomethyl)-pyrrolidine;   (x) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(cyclohexylmethylthiomethyl)-pyrrolidine;   (xi) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(cyclopentylthiomethyl)-pyrrolidine;   (xii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(phenylthiomethyl)-pyrrolidine;   (xiii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(4-fluorophenylthiomethyl)-pyrrolidine;   (xiv) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(4-chlorophenylthiomethyl)-pyrrolidine;   (xv) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(3-chlorophenylthiomethyl)-pyrrolidine;   (xvi) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(4-methylphenylthiomethyl)-pyrrolidine;   (xvii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(3-methylphenylthiomethyl)-pyrrolidine;   (xviii) (3S,4R)-1-[(9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(benzylthiomethyl)-pyrrolidine;   (xix) (3S,4S)-1-[(9-deazaguanin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (xx) (3S,4R)-1-[(9-deazaguanin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (xxi) (3S,4S)-1-[(9-deazahypoxanthin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (xxii) (3S,4R)-1-[(9-deazahypoxanthin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (xxiii) (3S,4S)-1-[(9-deazaxanthin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (xxiv) (3S,4S)-1-[(9-deazaxanthin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (xxv) (3S,4S)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (xxvi) (3S,4S)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxymethyl-pyrrolidine;   (xxvii) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(benzylthiomethyl)-pyrrolidine;   (xxviii) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (xxix) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(ethylthiomethyl)-pyrrolidine;   (xxx) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(propylthiomethyl)-pyrrolidine;   (xxxi) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(isopropylthiomethyl)-pyrrolidine;   (xxxii) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(butylthiomethyl)-pyrrolidine;   (xxxiii) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(phenylthiomethyl)-pyrrolidine;   (xxxiv) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(4-fluorophenylthiomethyl)-pyrrolidine;   (xxxv) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(4-chlorophenylthiomethyl)-pyrrolidine;   (xxxvi) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(3-chlorophenylthiomethyl)-pyrrolidine;   (xxxvii) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(4-methylphenylthiomethyl)-pyrrolidine;   (xxxviii) (3S,4R)-1-[(8-aza-9-deazaadenin-9-yl)ethyl]-3-hydroxy-4-(3-methylphenylthiomethyl)-pyrrolidine;   (xxxix) (3S,4S)-1-[(8-aza-9-deazaguanin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (xl) (3S,4S)-1-[(8-aza-9-deazaguanin-9-yl)ethyl]-3-hydroxymethyl-pyrrolidine;   (xli) (3S,4S)-1-[(8-aza-9-deazaguanin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (xlii) (3S,4S)-1-[(8-aza-9-deazahypoxanthin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine;   (xliii) (3S,4S)-1-[(8-aza-9-deazahypoxanthin-9-yl)ethyl]-3-hydroxy-4-methyl-pyrrolidine;   (xliv) (3S,4S)-1-[(8-aza-9-deazahypoxanthin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine;   (xlv) (3S,4S)-1-[(8-aza-9-deazaxanthin-9-yl)ethyl]-3-hydroxy-4-(hydroxymethyl)-pyrrolidine; and   (xlvi) (3S,4S)-1-[(8-aza-9-deazaxanthin-9-yl)ethyl]-3-hydroxy-4-(methylthiomethyl)-pyrrolidine.   
 
         [0076]    In a second aspect of the invention there is provided a pharmaceutical composition comprising a pharmaceutically effective amount of a compound of formula (I). 
         [0077]    In another aspect of the invention there is provided a method of treatment of a disease or condition in which it is desirable to inhibit purine phosphoribosyltransferase, purine nucleoside phosphorylase, 5′-methylthioadenosine phosphorylase, 5′-methylthioadenosine nucleosidase and/or nucleoside hydrolase comprising administering a pharmaceutically effective amount of a compound of formula (I) to a patient requiring treatment. 
         [0078]    The diseases or conditions include cancer, bacterial and protozoal infections, and T-cell mediated diseases such as psoriasis, arthritis and transplant rejection. 
         [0079]    In a further aspect of the invention there is provided the use of a compound of formula (I) in the manufacture of a medicament for the treatment of one or more of these diseases or conditions. 
         [0080]    In still a further aspect of the invention there is provided a method of preparing a compound of formula (I). 
     
    
     DETAILED DESCRIPTION 
     Definitions 
       [0081]    The term “alkyl” is intended to include both straight- and branched-chain alkyl groups. The same terminology applies to the non-aromatic moiety of an aralkyl radical. Examples of alkyl groups include: methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, t-butyl group, n-pentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1-ethylpropyl group, 2-ethylpropyl group, n-hexyl group and 1-methyl-2-ethylpropyl group. 
         [0082]    The term “aryl” means an aromatic radical having 4 to 18 carbon atoms and includes heteroaromatic radicals. Examples include monocyclic groups, as well as fused groups such as bicyclic groups and tricyclic groups. Some examples include phenyl group, indenyl group, 1-naphthyl group, 2-naphthyl group, azulenyl group, heptalenyl group, biphenyl group, indacenyl group, acenaphthyl group, fluorenyl group, phenalenyl group, phenanthrenyl group, anthracenyl group, cyclopentacyclooctenyl group, and benzocyclooctenyl group, pyridyl group, pyrrolyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazolyl group, tetrazolyl group, benzotriazolyl group, pyrazolyl group, imidazolyl group, benzimidazolyl group, indolyl group, isoindolyl group, indolizinyl group, purinyl group, indazolyl group, furyl group, pyranyl group, benzofuryl group, isobenzofuryl group, thienyl group, thiazolyl group, isothiazolyl group, benzothiazolyl group, oxazolyl group, and isoxazolyl group. 
         [0083]    The term “aralkyl” means an alkyl radical bearing an aryl substituent. 
         [0084]    The term “halogen” includes fluorine, chlorine, bromine and iodine. 
         [0085]    The term “optionally substituted” means, in reference to the optionally substituted group, that that group may carry one or more substituent chosen from amongst an alkyl group, an alkoxy group (wherein the alkyl group is as defined above), a halogen atom, an amino group, carboxylic acid group, an carboxylate alkyl ester group, or an alkylthio group. 
         [0086]    The term “prodrug” as used herein means a pharmacologically acceptable derivative of the compound of formula (I), such that an in vivo biotransformation of the derivative gives the compound as defined in formula (I). Prodrugs of compounds of formula (I) may be prepared by modifying functional groups present in the compounds in such a way that the modifications are cleaved in vivo to give the parent compound. 
         [0087]    The term “pharmaceutically acceptable salts” is intended to apply to non-toxic salts derived from inorganic or organic acids, including, for example, the following acid salts: acetate, adipate, alginate, aspartate, benzoate, benzenesulfonate, bisulfate, butyrate, citrate, camphorate, camphorsulfonate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptanoate, glycerophosphate, glycolate, hemisulfate, heptanoate, hexanoate, hydrochloride, hydrobromide, hydroiodide, 2-hydroxyethanesulfonate, lactate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oxalate, palmoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, p-toluenesulfonate, salicylate, succinate, sulfate, tartrate, thiocyanate, and undecanoate. 
         [0088]    The term “patient” includes human and non-human animals. 
       Description of Inhibitor Compounds 
       [0089]    The ethylene-linked compounds of the invention are surprisingly potent inhibitors of PNP. A class of PNP inhibitor compounds containing methylene linkages is described in the applicants&#39; PCT application PCT/NZ03/00186. The methylene-linked compounds were designed to match the fully dissociated transition states of human PNP and  Plasmodium falciparum  PNP. The applicants have carried out detailed investigations of this methylene-linked class. 
         [0090]    Based on their particular knowledge of the PNP enzyme, and the activities of the methylene-linked compounds, the applicants would not have predicted that ethylene-linked compounds would be potent PNP inhibitors, or would even exhibit PNP inhibitory activity at all. It was previously considered that the presence of the extra carbon atom in the linkage would have rendered the ethylene class inactive. It was thought that the inclusion of an extra carbon atom in the linkage would elongate the distance between the ribose mimic (the amine moiety) and the base moiety beyond the length that had been found to be optimum for inhibition of the PNP enzyme. The prior art and the applicants&#39; previous special knowledge of the PNP enzyme actually taught away from synthesising and investigating the activities of the ethylene-linked compounds. However, despite the linkage being outside of the predicted optimal length, the compounds of the invention prove to be surprisingly potent inhibitors of human PNP. Indeed, one compound of the invention (Compound 1) has a K i * for human PNP of 0.46±0.05 nM, a potency sufficient to have therapeutic potential. 
       Synthesis of Inhibitor Compounds 
       [0091]    The compounds may be prepared by any method. However, preferably they are prepared by independently synthesising the amine moiety and the base part, and then linking the base part to the nitrogen atom in the ring of the amine moiety. In one preferred embodiment, the ethylene linkage is constructed on the base part in the form of a 2-substituted acetaldehyde moiety, and then linked to the amine moiety by way of a reductive amination reaction. 
       General Aspects 
       [0092]    The compounds of the invention are useful in both free base form and in the form of salts. 
         [0093]    It will be appreciated that the representation of a compound of formula (I), where B and/or D is a hydroxy group, is of the enol-type tautomeric form of a corresponding amide, and this will largely exist in the amide form. The use of the enol-type tautomeric representation is simply to allow fewer structural formulae to represent the compounds of the invention. 
         [0094]    The active compounds may be administered to a patient by a variety of routes, including orally, parenterally, by inhalation spray, topically, rectally, nasally, buccally or via an implanted reservoir. The amount of compound to be administered will vary widely according to the nature of the patient and the nature and extent of the disorder to be treated. Typically the dosage for an adult human will be in the range less than 1 to 1000 milligrams, preferably 0.1 to 100 milligrams. The specific dosage required for any particular patient will depend upon a variety of factors, including the patient&#39;s age, body weight, general health, sex, etc. 
         [0095]    For oral administration the compounds can be formulated into solid or liquid preparations, for example tablets, capsules, powders, solutions, suspensions and dispersions. Such preparations are well known in the art as are other oral dosage regimes not listed here. In the tablet form the compounds may be tableted with conventional tablet bases such as lactose, sucrose and corn starch, together with a binder, a disintegration agent and a lubricant. The binder may be, for example, corn starch or gelatin, the disintegrating agent may be potato starch or alginic acid, and the lubricant may be magnesium stearate. For oral administration in the form of capsules, diluents such as lactose and dried cornstarch may be employed. Other components such as colourings, sweeteners or flavourings may be added. 
         [0096]    When aqueous suspensions are required for oral use, the active ingredient may be combined with carriers such as water and ethanol, and emulsifying agents, suspending agents and/or surfactants may be used. Colourings, sweeteners or flavourings may also be added. 
         [0097]    The compounds may also be administered by injection in a physiologically acceptable diluent such as water or saline. The diluent may comprise one or more other ingredients such as ethanol, propylene glycol, an oil or a pharmaceutically acceptable surfactant. 
         [0098]    The compounds may also be administered topically. Carriers for topical administration of the compounds of include mineral oil, liquid petrolatum, white petrolatum, propylene glycol, polyoxyethylene, polyoxypropylene compound, emulsifying wax and water. The compounds may be present as ingredients in lotions or creams, for topical administration to skin or mucous membranes. Such creams may contain the active compounds suspended or dissolved in one or more pharmaceutically acceptable carriers. Suitable carriers include mineral oil, sorbitan monostearate, polysorbate 60, cetyl ester wax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol and water. 
         [0099]    The compounds may further be administered by means of sustained release systems. For example, they may be incorporated into a slowly dissolving tablet or capsule. 
       EXAMPLES 
       [0100]    The following examples further illustrate the invention. It is to be appreciated that the invention is not limited to the examples. 
       Example 1 
     Synthesis of (3S,4S)-1-[2-(9-Deaza-hypoxanthin-9-yl)ethyl]-3-hydroxy-4-hydroxymethylpyrrolidine (1) [DAD-Et-Immucillin-H] 
       [0101]    
       
                 
         
             
             
         
       
     
         [0102]    n-Butyllithium (5.30 mL of a 1.3 M solution in hexanes, 6.90 mmol) was added to a solution of bromide 1a (2.00 g, 5.75 mmol) in diethyl ether (40 mL) and anisole (16 mL) under argon at −78° C. Thin-layer chromatography confirmed that no starting material remained. Dimethylformamide (4.4 mL, 57.5 mmol) was added and the mixture stirred at −78° C. for 30 minutes then the mixture was allowed to warm to room temperature. Dichloromethane (200 mL) was added and the solution was washed with water (100 mL), dried and the solvent was removed. The residue was chromatographed on silica gel to give compound 1b (1.20 g, 70%) as a white solid. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0103]    Methyltriphenylphosphonium bromide (1.20 g, 3.37 mmol) was suspended in tetrahydrofuran (25 mL) and cooled to −78° C. under an atmosphere of argon. n-Butyllithium (1.94 mL of a 1.3 M solution in hexanes, 2.52 mmol) was added to give a yellow solution, which was stirred for 15 minutes. Aldehyde 1b (0.500 g, 1.68 mmol) was added as a solid and the solution was allowed to warm to room temperature then stirred for 2 hours. The solvent was removed and the residue was chromatographed on silica gel to give compound 1c (0.450 g, 91%) as a pale yellow solid. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0104]    Borane dimethyl sulfide (3.12 mL, 32.9 mmol) was added to a solution of alkene 1c (0.970 g, 3.29 mmol) in tetrahydrofuran (11 mL) under an atmosphere of argon and the solution was stirred for 18 hours at room temperature. Sodium hydroxide (1.97 g, 49.3 mmol) was dissolved in water (4 mL) then diethyl ether (2 mL) was added slowly to the solution at 0° C. 30% Aqueous hydrogen peroxide (30% w/w, 8 mL) was added slowly and the mixture was stirred at room temperature for 3 hours. Dichloromethane (100 mL) was added and the mixture was washed with water (100 mL), dried and the solvent was removed. Chromatography of the residue on silica gel gave compound 1d (0.670 g, 65%) as a white solid. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0105]    Dess-Martin periodinane (176 mg, 0.415 mmol) was added to a solution of alcohol 1d (100 mg, 0.319 mmol) in dichloromethane (2 mL) at room temperature giving a yellow precipitate. The mixture was stirred for 10 minutes then chromatographed on silica gel to give compound 1e (41 mg, 41%). This reaction was repeated with 460 mg of alcohol 1d, but was left for only 2 minutes with the oxidant and purification was carried out quickly. The yield of compound 1e increased to 71%, although this material was shown to be not as pure by NMR spectroscopy. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0106]    Aldehyde 1e (110 mg, 0.354 mmol) was added to a solution of amine 1f (60 mg, 0.389 mmol; reference 1) in methanol (1 mL) at room temperature and the solution stirred for 15 minutes. Sodium cyanoborohydride (29 mg, 0.460 mmol) was then added to the solution, which was stirred for an additional 30 minutes. The mixture was adsorbed onto silica and chromatographed on silica gel giving compound 1g (20 mg, 14%) as a tan gum. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0107]    10% Palladium on carbon (20 mg) was added to a solution of 1g (13 mg, 0.0315 mmol) in ethanol (1 mL) and methanol saturated with ammonia (0.5 mL) and the mixture was stirred under an atmosphere of hydrogen at room temperature for 18 hours. The mixture was filtered and the solvent removed. The residue was chromatographed on silica gel to give compound 1h (5 mg, 54%) as a tan gum. 
         [0000]    
       
                 
         
             
             
         
       
     
         [0108]    Compound 1h (4 mg, 0.137 mmol) was heated to reflux in concentrated hydrochloric acid (1 mL) for 2 hours. The solvent was removed to give compound 1 (DAD-Et-Immucillin-H) hydrochloride salt (3 mg, 73%) as a white solid. 
       Example 2 
     Synthesis of (3S,4R)-1-[2-(9-Deaza-adenin-9-yl)ethyl]-3-hydroxy-4-methylthiomethylpyrrolidine (2) [Methylthio-DAD-Et-Immucillin-A] 
       [0109]    
       
                 
         
             
             
         
       
     
       3-Cyanopropyl benzoate (2b) 
       [0110]    A mixture of bromobutyronitrile (2a) (7.45 g, 50.3 mmol), sodium benzoate (14.5 g, 101 mmol), tetrabutylammonium hydrogen sulfate (34.2 g, 101 mmol) and molecular sieves (1 g) in dry acetone (100 ml) was heated under reflux for 4 hrs. The reaction mixture was cooled to RT and filtered through the celite pad and concentrated to dryness. Dichloromethane was added and the mixture was washed with sat. NaHCO 3  followed by water, dried and concentrated. Chromatography (EtOAc:petroleum ether, 1:4) afforded 9.5 g (100%) of (2a) as clear syrup.  1 H NMR (CDCl 3 ) δ 8.02-8.12 (m, 2H), 7.41-7.59 (m, 3H), 4.42 (t, 2H), 2.52 (t, 2H), 2.13 (m, 2H);  13 C NMR δ 171.5 (C), 166.7 (C), 134.0 (CH), 133.6 (CH), 130.5 (CH), 130.1 (CH), 130.0 (CH), 128.9 (CH), 119.3 (C), 63.1 (CH 2 ), 25.4 (CH 2 ), 14.8 (CH 2 ). 
       4-(Trityloxy)butanenitrile (2c) 
       [0111]    To a mixture of benzoate (2b) (9.5 g, 50.2 mmol) in methanol (80 ml) was added water (20 ml) and 2M NaOH (10 ml). After stirring for 1 hr at room temperature the reaction mixture was treated with 2M HCl (10 ml), stirred for 15 min and then was concentrated to dryness and dried in vacuo to afford a white solid which was used in the next step without further purification. The crude material in dry pyridine was treated with trityl chloride (10.49 g, 37.6 mmol), and the mixture was stirred at room temperature for 17 hrs and concentrated to dryness. Ethyl acetate was added and the mixture was washed twice with water, dried and concentrated. Chromatography (EtOAc:petroleum ether, 1:9) gave trityl derivative (2c), 15 g (91%) as a white solid.  1 H NMR (CDCl 3 ) δ 7.20-7.42 (m, 15H), 3.21 (t, 2H), 2.44 (t, 2H), 1.85-1.9 (m, 2H);  13 C NMR δ 147.3 (C), 144.3 (C), 128.9 (CH), 128.3 (CH), 127.6 (CH), 127.5 (CH), 119.9 (C), 87.2 (C), 61.7 (CH 2 ), 26.7 (CH 2 ), 14.8 (CH 2 ). 
       2-(Dimethylamino)methylene)-4-(trityloxy)butanenitrile (2d) 
       [0112]    Trityl derivative (2c) (1 g, 3.05 mmol) was dissolved in dry DMF (15 ml). Bredereck&#39;s reagent (0.84 g, 4.84 mmol) was added and the reaction mixture was stirred at 130° C. in a flask with a stopper for 1 hr. Bredereck&#39;s reagent (0.84 g, 4.84 mmol) was added once more and the mixture was stirred at 130° C. for 2 hrs and concentrated to dryness. Chromatography (EtOAc:petroleum ether, 1:4) gave dimethylamino derivative (2d), 0.73 g (62.5%) as a clear syrup.  1 H NMR (CDCl 3 ) δ 7.21-7.45 (m, 15H), 6.25 (s, 1H), 3.17 (t, 2H), 3.00 (s, 6H), 2.26 (t, 2H);  13 C NMR δ 151.2 (CH), 144.7 (C), 129.1 (CH), 128.2 (CH), 127.3 (CH), 122.9 (C), 87.0 (C), 69.7 (C), 63.9 (CH 2 ), 34.5 (CH 3 ), 28.4 (CH 2 ). 
       (E/Z)-3-(Cyanomethylamino)-2-(trityloxymethyl)acrylonitrile (2e) 
       [0113]    Compound (2d) (0.722 g, 1.888 mmol) was dissolved in dry methanol (50 ml). Sodium acetate (1.239 g, 15.10 mmol) and aminoacetonitrile bisulfate (1.164 g, 7.55 mmol) were added and the reaction mixture was stirred under reflux for 5 hrs. The mixture was concentrated to dryness. Chloroform was added, and the reaction mixture was then washed twice with water, dried and concentrated. Chromatography (EtOAc:petroleum ether, 1:2) gave a mixture of cis-trans isomers (2e), 0.74 g (100%) as a pale yellow foam.  1 H NMR (CDCl 3 ) δ 7.22-7.44 (m, 30H), 6.61 (d, J=12.0 Hz, 1H), 6.43 (d, J=12.6 Hz, 1H), 5.86-5.94 (m, 1H), 4.79-4.85 (m, 1H), 3.89 (d, J=6.1 Hz, 2H), 3.66 (d, J=6.1 Hz, 2H), 3.35 (t, 2H), 3.18 (t, 2H), 2.26-2.32 (m, 4H);  13 C NMR δ 146.7 (CH), 146.6 (CH), 143.0 (C), 142.2 (C), 127.6 (CH), 127.1 (CH), 126.9 (CH), 126.5 (CH), 126.1 (CH), 121.0 (C), 114.9 (C), 114.8 (C), 87.0 (C), 85.8 (C), 81.3 (C), 79.3 (C), 62.7 (CH 2 ), 61.5 (CH 2 ), 34.2 (CH 2 ), 33.9 (CH 2 ), 30.1 (CH 2 ), 27.7 (CH 2 ). 
       3-Amino-4-(2-(trityloxy)ethyl)-1H-pyrrole-2-carbonitrile (2f) 
       [0114]    DBU (1.7 ml, 11.28 mmol) was added to a stirred solution of nitrile (2e) (0.74 g, 1.88 mmol) in dry dichloromethane at room temperature. Methyl chloroformate (0.44 ml, 5.64 mmol) was added drop wise and the reaction mixture was stirred at RT for 17 hrs. Methanol (4 ml) was then added and after 1 hr the resulting solution was diluted with dichloromethane (150 ml), washed with 2M HCl (20 ml), followed by aq. sodium bicarbonate (30 ml), dried (MgSO 4 ), and concentrated in vacuo to afford a syrup. Chromatography (ethyl acetate:petroleum ether, 1:2) gave pyrrole (2f), 0.508 g (68.6%) as a clear syrup.  1 H NMR (CDCl 3 ) δ 7.86 (s, 1H), 7.13-7.31 (m, 15H), 6.35 (d, J=3.1 Hz, 1H), 3.18 (t, 2H); 2.49 (t, 2H);  13 C NMR δ 142.9 (C), 141.8 (C), 127.7 (CH), 126.8 (CH), 126.1 (CH), 121.3 (CH), 114.2 (C), 110.3 (C), 86.2 (C), 63.4 (CH 2 ), 23.9 (CH 2 ). 
       7-(2-(Trityloxy)ethyl)-5H-pyrrolo[3,2-d]pyrimidin-4-amine (2g) 
       [0115]    Pyrrole (2f) (0.480 g, 1.220 mmol) was dissolved in abs EtOH (15 ml). Formamidine acetate (0.635 g, 6.10 mmol) was added and the reaction mixture was heated under reflux for 4 hrs. The solution was concentrated to dryness. Chromatography (ethyl acetate) gave (2g), 0.42 g (82%) as a solidified syrup.  1 H NMR (MeOH-d 4 ) δ 8.47 (s, 1H), 7.54 (s, 1H), 7.12-7.41 (m, 15H), 3.30-3.35 (m, 2H); 3.0 (t, 2H);  13 C NMR δ 152.8 (C), 149.6 (CH), 146.0 (C), 144.6 (C), 130.2 (CH), 130.0 (CH), 129.0 (CH), 128.3 (CH), 115.3 (C), 114.0 (C), 88.2 (C), 65.1 (CH 2 ), 25.8 (CH 2 ). 
       N-Benzoyl-N-(7-(2-(trityloxy)ethyl)-5H-pyrrolo[3,2-d]pyrimidin-4-yl)benzamide (2h) 
       [0116]    Pyrrolo-pyrimidine (2f) (0.4 g, 0.951 mmol) was dissolved in dry pyridine (15 ml) and cooled to 0° C. Benzoyl chloride (2 ml, 17.22 mmol) was added and the reaction mixture was stirred at RT for 17 hrs. The resulting solution was diluted with dichloromethane, washed with water, followed by aq. sodium bicarbonate, dried (MgSO 4 ), and concentrated in vacuo to afford a syrup. Chromatography (ethyl acetate:petroleum ether, 1:4) gave over-N-benzoylated material as a syrup. This was dissolved in dry MeOH (20 ml) and treated with triethylamine (1 ml). The solution was stirred at RT for 17 hrs and concentrated to dryness. Chromatography (ethyl acetate:petroleum ether, 1:2) gave (2h), 0.53 g (89%) as a white foam.  1 H NMR (CDCl 3 ) δ 8.4 (s, 1H), 8.1 (m, 1H), 7.8-8.0 (m, 4H), 7.13-7.49 (m, 21H), 3.4 (t, 2H); 3.1 (t, 2H);  13 C NMR d 171.5 (C), 167.5 (C), 151.7 (C), 148.8 (CH), 144.8 (C), 142.8 (C), 133.8 (CH), 132.2 (CH), 131.3 (CH), 130.4 (CH), 130.2 (CH), 129.1 (CH), 128.7 (CH), 128.5 (CH), 128.1 (CH), 127.3 (CH), 116.3 (C), 114.4 (C), 87.0 (C), 63.9 (CH 2 ), 24.9 (CH 2 ). 
       N-Benzoyl-N-(7-(2-hydroxyethyl)-5H-pyrrolo[3,2-d]pyrimidin-4-yl)benzamide (2i) 
       [0117]    N-Benzoyl derivative (2h) (0.2 g, 0.318 mmol) was dissolved in aq. acetic acid (80%, 5 ml) and stirred at 60° C. for 4 hrs. The resulting solution was concentrated in vacuo to afford a syrup. Chromatography (ethyl acetate:pethroleum ether, 1:1) gave (9), 111 mg (90%) as a clear syrup. 
       N-Benzoyl-N-(7-(2-oxoethyl)-5H-pyrrolo[3,2-d]pyrimidin-4-yl)benzamide (2j) 
       [0118]    Alcohol (21) (78 mg, 202 μmol) was dissolved in dry dichloromethane (5 ml) and treated with Dess-Martin periodinane (1.5 eq., 128 mg). The reaction mixture was stirred at RT for 1 hr. The resulting solution was diluted with ether and treated with 1M NaOH. After 15 min the organic layer was washed with water, dried (MgSO 4 ) and concentrated in vacuo to afford a syrup. Chromatography (ethyl acetate:petroleum ether, 1:1) gave (2j), 71 mg (92%) as a clear syrup. 
       (3S,4R)-1-[2-(9-Deaza-adenin-9-yl)ethyl]-3-hydroxy-4-methylthiomethylpyrrolidine (2) [Methylthio-DAD-Et-Immucillin-A] 
       [0119]    Acetaldehdo-derivative (2j) can be coupled with the (3S,4R)-3-hydroxy-4-methylthiomethylpyrrolidine (2k) by reductive amination using sodium cyanoborohydride in methanol at room temperature, following methodology reported in Evans et al,  J. Med. Chem.,  48 (2005) 4679-4689, (see Scheme 1), and the N-benzoyl protecting groups can then be removed by treatment of the product with methanolic ammonia, to yield the title compound (2). 
       Example 3 
     Inhibition Studies 
       [0120]    Initial (K i ) and equilibrium (K i *) dissociation constants of DAD-Et-Immucillin-H were determined for human PNP. 
         [0121]    Inhibitor dissociation constants for the phosphorolysis of inosine were based on initial and equilibrium reaction rate measurements with varied inhibitor concentrations (Miles, R. W., Tyler, P. C., Furneaux, R. H., Bagdassarian, C. K. and Schramm, V. L. (1998) One-third-the-sites transition state inhibitors for purine nucleoside phosphorylase,  Biochemistry  37, 8615-8621; Morrison, J. F. and Walsh, C. T. (1988) The behaviour and significance of slow-binding enzyme inhibitors,  Adv. Enzymol. Relat. Areas Mol. Biol.  61, 201-301). Reactions were started by adding huPNP (1.4 nM) to reaction mixtures (25° C.) containing 1 mM inosine in 50 mM KHPO 4  pH 7.4 with xanthine oxidase at 60 mU/ml. Hypoxanthine formed by phosphorolysis of inosine was oxidized to uric acid and monitored spectrophotometrically at 293 nm (extinction coefficient for uric acid ε 293 =12.9 mM −1 cm −1 ). Enzyme concentration was adjusted to give absorbance changes not exceeding 1.0 during the time required to characterize initial and final slow-onset inhibition equilibria. The large excess of substrate and continuous product depletion provided extended initial rate conditions. In most cases the concentration of the inhibitor compound was &gt;10-fold greater than the enzyme concentration as required for simple analysis of two-state slow-onset tight-binding inhibition (Morrison, J. F. and Walsh, C. T. (1988) The behavior and significance of slow-binding enzyme inhibitors,  Adv. Enzymol. Relat. Areas Mol. Biol.  61, 201-301). The inhibition constant K i ; describes the reversible equilibrium between enzyme and inhibitor (compound 1) for the initial inhibitor binding step. K i  was determined by fitting the initial rates at different inhibitor concentration to the equation for competitive inhibition: ν i =(k cat ×S)/(K m (1+I/K i )+S), where μ i  is initial reaction rate, k cat  is the catalytic turnover number, K m  is the Michaelis constant, K i  is the dissociation constant of enzyme-inhibitor complex (EI), I is inhibitor concentration and S is substrate concentration. The dissociation constant for the complex formed after slow onset equilibrium (K i *) was determined by ν=(k cat ×S)/(K m (1+I/K i *)+S), where ν is the steady state reaction rate and the other variables are the same as above. 
         [0122]    Initial (K i ) and equilibrium (K i *) dissociation constants of Compound 1 for huPNP were found to be 1.6±0.3 nM and 0.46±0.05 nM, respectively. 
         [0123]    Although the invention has been described by way of example, it should be appreciated the variations or modifications may be made without departing from the scope of the invention. Furthermore, when known equivalents exist to specific features, such equivalents are incorporated as if specifically referred to in the specification. 
       INDUSTRIAL APPLICABILITY 
       [0124]    The present invention relates to compounds that are inhibitors of PNP, PPRT, MTAP, MTAN and/or NH. The compounds are therefore expected to be useful in the treatment of diseases in which the inhibition of PNP, PPRT, MTAP, MTAN and/or NH is desirable. Such diseases include cancer, and bacterial infection, protozoal infection or T-cell mediated diseases.