ANTIVIRAL COMPOUNDS

Abstract: Compounds of formula (wherein X is oxygen or sulphur and n is 0 or 1) and physiologi­ cally acceptable salts and esters thereof, have been found to have good activity in vivo against herpes viruses particularly herpes simplex.

Description: Antiviral Compounds The present invention relates to novel purine derivatives having valuable antiviral activity particularly against viruses of the herpes family. U.K. Patent Specification No. 1523865 describes a broad class of purine derivatives containing an acyclic side chain in the 9-position. These purine derivatives have been found to have antiviral activity aginst various classes of DNA viruses particularly against herpes viruses such as herpes simplex. Among these derivatives, 9-(2-hydroxyethoxymethyl)guanine (otherwise known as acyclovir) has been found to have particularly good activity against herpes simplex virus. Other purine derivatives containing an acyclic side chain in the 9position have also been described including for example analogues of acyclovir containing a 2-hydroxy-1-hydroxymethylethoxymethyl group in the 9-position, described in UK Patent Specification No. 2104070A and acyclovir analogues which are unsubstituted at the 6-position, as described in UK Patent Specification No. 2150204A. We have now discovered advantageous antiviral activity in a new class of 6-H analogues of acyclovir as described below. According to the present invention we provide a compound of the formula. EMI1.1 (wherein X is oxygen or sulphur and n is O or 1) and physiologically acceptable salts and esters thereof. The present invention thus includes compounds of formula (I) wherein n is 0 and also compounds of formula (I) wherein n is 1 and X is oxygen or sulphur and physiologically acceptable salts and esters thereof. Salts of the compound of formula (I) which may be conveniently used in therapy include physiologically acceptable salts of organic acids as lactic, acetic, malic or p-toluenesulphonic acid as well as physiologically acceptable salts of mineral acids such as hydrochloric or sulphuric acid. Esters of the compound of formula (I) which may be conveniently used in therapy include those containing a formyloxy or C1 16 (for example C1 6) branched or straight chain alkanoyloxy (e.g. acetoxy or propionyloxy), optionally substituted aralkanoyloxy (e.g. phenyl-C1 4alkanoyloxy such as phenyl-acetoxy) or optionally substituted aroyloxy (e.g. benzoyloxy or naphthoyloxy) or phosphate ester grouping at one or both of the terminal positions of the 9-side chain of the compounds of formula (I). The above-mentioned aralkanoyloxy and aroyloxy ester groups may be substituted, for example by one or more halogen (e.g. chlorine or bromine) atoms or amino, nitrile or sulphamido groups, the aryl moiety of the grouping advantageously containing 6 to 10 carbon atoms. According to a further feature of the present invention we provide a compound of formula (I) and physiologically acceptable salts and esters thereof for use in therapy for example in the treatment or prophylaxis of a viral disease in an animal, e.g. a mammal such as man. The present invention also provides a method for the treatment or prophylaxis of a viral disease in an animal, e.g. a mammal such as man which comprises administering to the animal an effective antiviral amount of the compound of formula (I) or a physiologically acceptable salt or ester thereof. The present invention further provides the use of a compound of formula (I) or a physiologically acceptable salt or ester thereof in the manufacture of a medicament for the treatment or prophylaxis of a viral disease. The compounds of formula (I) and their physiologically acceptable salts and esters have a particularly effective activity in vivo against DNA viruses particularly those of the herpes family which includes herpes simplex, varicella zoster, cytomegalovirus and Epstein-Barr virus,as well as hepatitis B. The compound of formula (I) and the physiologically acceptable salts and esters thereof (hereafter collectively referred to as the active ingredients) may be administered by any route appropriate to the condition to be treated, suitable routes including oral, rectal, nasal, topical (including buccal and sublingual), vaginal and parenteral (including subcutaneous, intramuscular, intravenous, intradermal, intrathecal and epidural). It will be appreciated that the preferred route may vary with for example the condition of the recipient. For each of the above-indicated utilities and indications the amount required of an active ingredient (as above defined) will depend upon a number of factors including the severity of the condition to be treated and the identity of the recipient and will ultimately be at the discretion of the attendant physician or veterinarian. In general however, for each of these utilities and indications, a suitable, effective dose will be in the range 0.1 to 250mg per kilogram bodyweight of recipient per day, preferably in the range 1 to 100mg per kilogram bodyweight per day and most preferably in the range 5 to 20mg per kilogram bodyweight per day; an optimum dose is about 10mg per kilogram bodyweight per day. (Unless otherwise indicated all weights of active ingredient are calculated as the parent compound of formula (I): for salts and esters thereof the figures would be increased proportionately.) The desired dose is preferably presented as two, three, four or more sub-doses administered at appropriate intervals throughout the day. These sub-doses may be administered in unit dosage forms, for example, containing 10 to 1000mg, preferably 20 to 500mg and most preferably 100 to 400mg of active ingredient per unit dosage form. While it is possible for the active ingredients to be administered alone it is preferable to present them as pharmaceutical formulations. The formulations, both for veterinary and for human use, of the present invention comprise at least one active ingredient, as above defined, together with one or more acceptable carriers therefor and optionally other therapeutic ingredients. The carrier(s) must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof. The formulations include those suitable for oral, rectal, nasal, topical (including buccal and sublingual), vaginal or parenteral (including subcutaneous, intramuscular, intravenous, intradermal, intrathecal and epidural) administration. The formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. Such methods include the step of bringing into association the active ingredient with the carrier which constitutes one or more accessory ingredients. In general the formulations are prepared by uniformly and intimately bringing into association the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product. Formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution or a suspension in an aqueous liquid or a non-aqueous liquid; or as an oilin-water liquid emulsion or a water-in-oil liquid emulsion. The active ingredient may also be presented as a bolus, electuary or paste. A tablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, preservative, surface active or dispersing agent. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active ingredient therein. For infections of the eye or other external tissues e.g. mouth and skin, the formulations are preferably applied as a topical ointment or cream containing the active ingredient in an amount of, for example, 0.075 to 20% w/w, preferably 0.2 to 15% w/w and most preferably 0.5 to 10% w/w. Formulations suitable for topical administration to the eye also include eye drops wherein the active ingredient is dissolved or suspended in a suitable carrier, especially an aqueous solvent for the active ingredient. The active ingredient is preferably present in such formulations in a concentration of 0.5 to 20%, advantageously 0.5 to 10% particularly about 1.5% wiw. Formulations suitable for topical administration in the mouth include lozenges comprising the active ingredient in a flavoured basis, usually sucrose and acacia or tragacanth; pastilles comprising the active ingredient in an inert basis such as gelatin and glycerin, or sucrose and acacia; and mouthwashes comprising the active ingredient in a suitable liquid carrier. Formulations for rectal administration may be presented as a suppository with a suitable base comprising for example cocoa butter or a salicylate. Formulations suitable for nasal administration wherein the carrier is a solid include a coarse powder having a particle size for example in the range 20 to 500 microns which is administered in the manner in which snuff is taken, i.e. by rapid inhalation through the nasal passage from a container of the powder held close up to the nose. Suitable formulations wherein the carrier is a liquid, for administration as for example a nasal spray or as nasal drops, include aqueous or oily solutions of the active ingredient. Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the active ingredient such carriers as are known in the art to be appropriate. Formulations suitable for parenteral administration include aqueous and nonaqueous sterile injection solutions which may contain anti-oxidants, buffers, bacteriostats and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example sealed ampoules and vials, and may be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described. Preferred unit dosage formulations are those containing a daily dose or unit daily sub-dose, as herein above recited, or an appropriate fraction therof, of an active ingredient. It should be understood that in addition to the ingredients particularly mentioned above the formulations of this invention may include other agents conventional in the art having regard to the type of formulation in question, for example those suitable for oral administration may include flavouring agents. The compounds of formula (I) and its their physiologically acceptable salts and esters may be prepared in conventional manner by analogous processes for preparing compounds of similar structure, such as those methods described in U.K. Patent Specification Nos. 1523865, 2104070 and 2130204. According to a further feature of the present invention there is provided a process for preparing the compounds of formula (I) and physiologically acceptable salts and esters thereof, characterised in that: a) one deblocks a compound of formula EMI6.1 (wherein X and n are as hereinbefore defined, R1 represents an amino or blocked amino group, R2 and R3 which may be the same or different, each represents a hydroxy or blocked hydroxy group, providing at least one of R1, R2 and R3 represents a blocked group) or a salt or ester thereof; b) one converts a compound of formula EMI6.2 (wherein X and n are as defined above and M represents a hydrogen atom or a radical convertible to a hydrogen atom and G represents a radical convertible to an amino group or (when M represents a radical as defined above) an amino group) or a salt or ester thereof, into the compound of formula (I) or a salt or ester thereof; c) reacting a compound of formula EMI6.3 (wherein Q represents a leaving group or atom) with a compound of formula EMI6.4 7 (wherein n and X is as defined above,- R is a blocking group and A represents a leaving group or atom); (d) a compound of formula EMI7.1 (wherein R4 is a precursor group for the CH2(X)n CH2 CH(OH) CH2 OH group) is converted into the desired compound of formula (I) or a salt or ester thereof; (e) a ring is closed in a precursor compound having either the pyrimidine or imidazole ring incompletely formed; and optionally effecting one or more of the following conversions, in any desired sequence:i) where the resulting product is a base, converting the said base into a physiologically acceptable acid addition salt thereof; ii) where the resulting product is an acid addition salt, converting the said salt into the parent base; iii) where the resulting product is the compound of formula (I) or a salt thereof converting the said compound or salt thereof into a physiologically acceptable ester of the said compound or salt; and iv) where the resulting product is an ester of the compound of formula (I), converting the said ester into the parent compound of formula (t), a physiologically acceptable salt thereof or a different physiologically acceptable ester thereof. In methods a) and c) the blocking groups may be selected, as appropriate, for example from acyl groups such as C14 alkanoyl groups e.g. acetyl or pivaloyl, or aroyl groups, e.g. benzoyl; arylmethyl groups e.g. benzyl; or tri-C1 4 alkylsilyl e.g. trimethysilyl. Arylmethyl blocking groups, may be removed for example by hydrogenolysis, e.g. by hydrogenation in the presence of Raney Nickel or palladium catalyst or by use of sodium in liquid ammonia. Acyl blocking groups may be removed for example by hydrolysis using for example an amine such as methylamine or triethylamine, advantageously in an aqueous medium. Trialkylsilyl blocking groups may be removed for example by solvolysis e.g. with alcoholic or aqueous ammonia, or by alcoholysis. Conversion of a compound of formula (III) into a compound of formula (I), by method b), can be achieved by various conventional means. For example G may represent an azide group which can be reduced to an amino group by catalytic hydrogenation using a suitable catalyst such as palladium. Alternatively, G may represent a halogen, e.g. chlorine, atom or a mercapto or thio (S=) group which can be converted into a hydrogen atom in a conventional manner, e.g. by catalytic hydrogenation using for example a palladium-charcoal catalyst. These processes together with other conventional processes are described in Fused Pyrimidines, Part II, Purines Ed. by D.J. Brown (1971), Willey-Intrescience. In process (c), the group Q in formula (IV) may for example represent a hydrogen atom; an acyl group, e.g. a Cl,rr alkanoyl group such as an acetyl group or an aroyl group such as a benzoyl group; or a tri-C14alkylsilyl group such as a trimethylsilyl group. The group A in formula (V) may for example represent a halogen atom (e.g. chlorine) or an acyloxy group wherein the acyl moiety may be for example a C1-4 alkanoyl group such as acetyl, or an aroyl group such as benzoyl. The reaction may be conveniently effected in a strong polar such as dimethyIformamide or hexamethylphosphoramide, advantageously in the presence of a base such as triethylamine or potassium carbonate. Alternatively, a thermal condensation may be effected by heating the compounds of formulae CIV) and (V) in the presence of a catalytic amount of a strong acid, e.g. sulphuric acid. With regard to process (d) R4 in formula (V') may be selected from various precursor groups for the desired end group including for example the following:i) -CH2CH2COCH2OH: this group may be converted into the desired group in conventional manner for example by treatment with sodium borohydride; ii) -CH2CH2CH(OR5)CH2(OR5) wherein at least one R5 group is an alkyl or aralkyl group, any other R5 being a hydrogen atom; the alkyl or aralkyl group may be converted into the desired group for example by treatment with HBr or BBr3 or catalytic hydrogenation in the presence of palladium charcoal. 6 iii) -CH2cH2CH(CH)CO2R6 wherein R represents a hydrogen atom or alkyl group; this group may be converted into the desired group for example by treatment with lithium aluminium hydride; iv) -CH2CH2CH(Y)CH2(Y) wherein Y represents halogen: EMI9.1 these groups may be converted into the desired group in conventional manner for example by hydrolysis; The preparation of the physiologically acceptable salts and esters of the compound of formula (I) may be effected in conventional manner, e.g. by appropriate esterification or salt-formation of the compound of formula (I). The optional conversions i)-iv) may also be carried out in conventional manner. The starting materials employed in the processes described above may also be prepared in conventional manner, e.g. in accordance with the processes described in the above-mentioned UK Patent Specifications. The following Examples illustrate the present invention. Example 1 a) 4-Bromo--1,2-dihydroxybutane monoformate A solution of 22.59 (0.167M) of 4-bromo-1-butene in 30ml of 98% formic acid and 17ml of 30% hydrogen peroxide was stirred at 40 C for 18 hours, then at room temperature for two days. The solution was evaporated in vacuo with a bath temperature of 400C to yield 28.48g of an oil (86%). The 'H NMR spectrum indicated the correct structure with the presence of a formate group. Mass spectrum gave the following fragments m/e 178 (M-H2O)+, 150 (M-CO2H2)+, 137 (M-CH2OCOH), 107 (Br-CH2CH2) and 71 (H COOCH=CH)+. b) 2-Amino-6-chloro-9-(3,4-dihydroxybutyl)-9H-purine A mixture of 3.0g (0.018M) of 2-amino-6-chloropurine, 4.2g (0.021M) of 4-bromo1,2-dihydroxybutane monoformate and 5.09 (0.036M) of potassium carbonate in 75ml of dry dimethylformamide was stirred at room temperature for 24 hrs. The mixture was filtered and the filtrate evaporated in vacuo. The residue was dissolved in methanol and combined with 5g of 70-230 mesh silica gel. After removal of solvent, the powder was applied to a column prepared for flash chromatography and the desired 9-isomer eluted with 10% methanol in ethyl acetate. The white solid obtained from evaporation of the eluate was recrytallised from ethyl acetate- hexane to give 1.669 (32%) after drying of the title compound, mp 178-1810C. The 'H NMR spectrum showed the presence of ethyl acetate but otherwise was consistent with the desired structure. The elemental analysis (CHNCl) indicated 1/5 molar amount of ethyl acetate with the correct structure. TLC (Silica gel in 12% MeOH tOAc) showed 1 spot. c) 2-A mino-9-(3,4-dihydroxybutyl)-9H-purine A mixture of 1.2g (4.2mM) of Z-amino4-chloro-9-(3,4-dihydroxybutyl)-9H- purine, 0.129 of palladium hydroxide, 2ml of triethylamine, 150ml methanol and 50ml of water was shaken on a Parr under an initial pressure of 50 p.s.i. of H2 for 2 days at room temperature. The mixture was filtered through a celite pad and the filtrate evaporated in vacuo. The residue was dissolved in 50ml of water and stirred for I hour at room temperature with 5.5g of strong OH anion exchange resin. The mixture was filtered through a celite pad, evaporated in vacuo and the residue redissolved in I ml of water. The aqiuedus solution was injected into a Waters preparative LC system-500 and chromatographed on a Waters Pre-Pak -500/C-18 reverse phase cartridge, eluting the desired compound with 5% acetonitrile in water. The solid obtained from the evaporated eluate was recrystallised from methanol-ethyl acetate to give 0.3029 of the title compound (32% after drying). mp = 140 142 0C. The elemental analysis and 'H NMR spectrum were consistent with the desired structure. Example 2 3-1(2-Amino-9H-purin-9-yl)methoxy-1 -1,2-propanediol a) 3-[2-Amino-6-chloro-9H-purin-9-yl)methoxy0-1,2-diacetoxypropane A mixture of 5.46 g (32.2mMO of 2-amino-6-chloropurine, 3.299 (24.9 mM) of ammonium sulfate, and 100ml of hexamethyldisilazane was refluxed for 4 hours and evaporated in vacuo to near dryness, then dissolved into about 200ml of dry toluene. To the mixture was added 9.189 (32.2 mM) of 3-0 (bromomethyl-1,2-diacetoxy)propanol and the solution was refluxed for 18 hours. The pH 1 mixture was neutralized using triethylamine followed by the addition of 95% ethanol, then heated for about 20 minutes and evaporated to near dryness. The mixture was partitioned between methylene chloride and water and the organic layer dried over MgS04, filtered and evaporated in vacuo to an amber oil which was purified by flash chromatoraphy on silica gel eluting with 100% CH2Cl2 and yielded 5.9749 (52%) of the alkylated 2-amino-6-chloropurine intermediate. b) 3-1(2-Amino-9H-purin-9-yl)methoxy]-1,2-diacetoxypropane A mixture of 4.2159 (11.8 mM) of 3-[(2-amino-6-chloro-9H-purin-9 yl)methoxyj-1,2-diacetoxypropane, 0.422 g palladium on carbon catalyst. (10% by weight), 140 ml of 1:1 ethanol-tetrahydrofuran, and 3.25ml triethylamine was shaken at initial pressure of 50 psi H2 on the Parr apparatus for 17 hours. The mixture was filtered and recharged with 0.8229 Pd/C and 2ml triethylamine under 53 psi H2 and shaken for an additional 19 hours. The celite filtered reaction mixture was evaporated to near dryness and then purified by flash chromatography on silica gel eluting with 50:30:20 Et20:Hexane:MeOH to yield 2.735 g (724b) of 3-[(2-amino 9H-purin-9-yl)methoxyl-1,2-diacetoxypropane c) 3-2-Amino-9H-purin-9-yl)methoxy] -1,2-propanediol 2.59 (7.732 mM) of 3-((2-amino-9H-purin-9-yl)methoxy]-1,2- diacetoxypropane was stirred at room temperature for ten minutes with 40 ml of aqueous methylamine. The reaction mixture was evaporated to half volume then extracted twice with methylene chloride to remove acetamide. The H20 product containing layer was evaporated to an oil which was recrystallised using methanol/acetone to yield 0.426g (34%) of the title compound as analytically pure product, mpt. 150-1530C, (overall yield 13%) The following Examples illustrate pharmaceutical formulations according to the invention in which the active compound is a compound of formula (I) Example 3 Tablet Active compound 200mg Lactose 235mg Starch 50mg Polyvinylpyrrolidone 50mg Magnesium stearate 5mg 500mg Mix the active compound with the lactose and starch and wet granuIate with a solution of the polyvinylpyrrolidone. Dry, sift, blend the granules with magnesium stearate and compress. Example 4 Capsule Active compound 200mg Lactose 184mg Sodium starch glycollate 8mg Polyvinylpyrrolidone 6mg Magnesium stearate 2mg Mix the active compound with the lactose and sodium starch glycollate and wet granulate with a solution of the polyvinylpyrrolidone. Dry, sift, blend the granules with the magnesium stearate and fill into hard gelatin capsules. Example 5 Cream Active compound 5.009 Glycerol 2.009 Cetostearyl alcohol 6.759 Sodium lauryl sulphate 0.75g White soft paraffin 12.509 Liquid paraffin 5.009 Chlorocresol 0.109 Purified water to 100.009 Dissolve the active compound in a mixture of purified water and glycerol and heat to 70 C. Heat the remaining ingredients together at 700C. Add the two parts together and emulsify. Cool and fill into containers. Example 6 Intravenous Injections A) Active compound 200mg Sodium hydroxide solution q.s. to pH 7.0 to 7.5 Water for injections to 5.0 ml Dissolve the active compound in part of the water for injections. Adjust the pH with the sodium hydroxide solution and make up to volume with additional water for injections. Under aseptic conditions, sterilise the solution by filtration, fill into sterile ampoules and seal the ampoules. B) Active compound 100mg Sodium hydroxide solution q.s. to pH 7.0 to 7.5 Mannitol 125mg Water for injections to 2.5ml Dissolve the active compound and mannitol in part of the water for injections. Adjust the pH with the sodium hydroxide solution and make up to volume with additional water for injections. Under aseptic conditions, sterilise the solution by filtration, fill into sterile vials and remove the water by freeze-drying. Seal the vials under an atmosphere of nitrogen and close with a sterile stopper and Antiviral Activity The compounds of Examples 1 and 2 were tested in vivo to determine their potency in vivo against herpes simplex infections. The compounds were tested in comparison with the 6-deoxy analogue of the compound of Example 1, namely 9 (3,4-dihydroxybutyl) guanine (DHi3G). The following is description of the testing. The compounds were tested in CD 1 mice infected with herpes simplex ICI cell culture stock having a titre of I x 105 plaque forming units (pfu)/ml and administered to the mice in a dose of 0.025ml by the intra-cerebral route. The test compounds were prepared as aqueous suspensions or solutions, each compound being administered at a dose of 50 mg/kg in a volume of 0.1 ml, by either the oral or sub-cutaneous (s.c.) route, to a treatment group of animals. Each group contained 10 animals for each compound and for each route of administration. Treatment of the animals commenced 2-3 hours after infection and continued twice daily for 4.5 days. A group of 13 animals which were infected but untreated served as controls. Survival times for the test animals were recorded over 14 days and expressed as mean reciprocol survival times (MRST). The results shown in the following table were obtained in which the figures in the column headed "Survival Times" indicate the number of animals that died on the day indicated in parentheses. TABLE Compound Survival Times MRST Example 1 (oral) 1(5), 4(6), 3(7), 1(7.5), 1(9) 0.154 Example 1 (s.c.) 7(6), 3(7) 0.160 Example 2 (oral) 1(6), 1(7), 1(8), 1(10.5) 5 survivors* 0 0.059 Example 2 (s.c.) 3(8), 1(9) 5 survivors* 0.054 DHBG (oral) 1(4.5), 3(5), 5(6), 1(7) 0.18 DHBG (s.c.) 1(5), 3(6), 5(7), 1(7.5) 0.155 (Controls) 6(4), 5(5), 2(6) 0.215 The above results indicate that the compounds of Examples 1 and 2 have a potent antiviral effect in vivo against HSV, particularly in comparison with the 6hydroxy analogue DHBG. * 1 mouse died within 24 hours of infection.

Claims: CLAIMS 1. Compounds of the general formula. EMI16.1 (wherein X is oxygen or sulphur and n is 0 or I) and physiologically acceptable salts and esters thereof. 2. Compounds as claimed in claim 1 wherein n is 0. 3. Compounds as claimed in claim 1 wherein n is 1. 4. Compounds as claimed in claim 3 wherein X is oxygen. 5. 2-Amino-9-(3,4-dihydroxybutyl)-9H-purine. 6. 3-[(2-Amino-9H-purin-9-yl)methoxy]-1, 2-propanediol. 7. A process for the preparation of compounds of formula (I) (as defined in claim 1) or a physiologically acceptable salt or ester thereof which comprises. a) deblocking a compound of formula EMI16.2 (wherein X and n are as defined in claim 1, R1 represents an amino or blocked amino group, R2 and R3 which may be the same or different, each represents a hydroxy or blocked hydroxy group, providing at least one of R1, R2 and R3 represents a blocked group) or a salt or ester thereof; b) converting a compound of formula EMI17.1 (wherein X and n are as defined in claim 1 and M represents a hydrogen atom or a radical convertible to a hydrogen atom and G represents a radical convertible to an amino group or (when M represents a radical as defined above) an amino group) or a salt or ester thereof, into a compound of formula (I) or a salt or ester thereof; c) reacting a compound of formula EMI17.2 (wherein Q represents a leaving group or atom) with a compound of formula EMI17.3 (wherein n and X is as defined in claim 1, R7 is a blocking group and A represents a leaving group or atom); (d) a compound of?formula EMI17.4 (wherein R4 is a precursor group for the CH2(X)n CH2 CH(OH) CH2 OH group) is converted into the desired compound of formula (I) or a salt or ester thereof; (e) a ring is closed in a precursor compound having either the pyrimidine or imidazole ring incompletely formed; and optionally effecting one or more of the following conversions, in any desired sequence:i) where the resulting product is a base, converting the said base into a physiologically acceptable acid addition salt thereof; ii) where the resulting product is an acid addition salt, converting the said salt into the parent base; iii) where the resulting product is the compound of formula (I) or a salt thereof converting the said compound or salt thereof into a physiologically acceptable ester of the said compound or salt; and iv) where the resulting product is an ester of the compound of formula (I), converting the said ester into the parent compound of formula (I), a physiologically acceptable salt thereof or a different physiologically acceptable ester thereof. 8. Pharmaceutical formulations comprising at least one compound as claimed in any of the preceding claims together with at least one pharmaceutical carrier or excipient. 9. A compound of formula (I) (as defined in claim 1) or a physiologically acceptable salt or ester thereof for use in therapy. 10. A compound of formula (I) (as defined in claim 1) or a physiologically acceptable salt or ester thereof for use in the treatment or prophylaxis of viral infections. 11. A compound of formula (I) (as defined in claim 1) or a physiologically acceptable salt or ester thereof for use in the treatment or prophylaxis of herpes simplex infections. CLAIMS 1. A process for the preparation of a compound of formula (I) EMI20.1 (wherein X is oxygen or sulphur and n is 0 or 1) or a physiologically acceptable salt or ester thereof,which comprises a) deblocking a compound of formula EMI20.2 (wherein X and n are as defined in claim 1, RX represents an amino or blocked amino group, R2 and R3 which may be the same or different, each represents a hydroxy or blocked hydroxy group, providing at least one of R1, R2 and R3 represents a blocked group) or a salt or ester thereof; b) converting a compound of formula EMI20.3 (wherein X and n are as defined in claim 1 and M represents a hydrogen atom or a radical convertible to a hydrogen atom and G represents a radical convertible to an amino group or (when M represents a radical as defined above) an amino group) or a salt or ester thereof, into a compound of formula (I) or a salt or ester thereof; c) reacting a compound of form EMI21.1 (wherein Q represents a leaving group or atom) with a compound of formula EMI21.2 (wherein n and X is as defined in claim 1, R7 is a blocking group and A represents a leaving group or atom); (d) a compound of formula EMI21.3 (wherein R4 is a precursor group for the CH2(X)n CH2 CH(OH) CH2 OH group) is converted into the desired compound of formula (I) or a salt or ester thereof; ; (e) a ring is closed in a precursor compound having either the pyrimidine or imidazole ring incompletely formed; and optionally effecting one or more of the following conversions, in any desired sequence:i) where the resulting product is a base, converting the said base into a physiologically acceptable acid- addition salt thereof; ii) where the resulting product is an acid addition salt, converting the said salt into the parent base; iii) where the resulting product is the compound of formula (I) or a salt thereof converting the said compound or salt thereof into a physiologically acceptable ester of the said compound or salt; and iv) where the resulting product is an ester of the compound of formula (I), converting the said ester into the parent compound of formula (I), a physiologically acceptable salt thereof or a different physiologically acceptable ester thereof. 2. A process for the preparation of compounds as claimed in claim 1 wherein n is 0. 3. A process for the preparation of compounds as claimed in claim 1 wherein n is 1. 4. A process for the preparation of compounds as claimed in claim 3 wherein X is oxygen. 5. A process for the preparation of 2-amino-9-(3,4-dihydroxybutyl)-9H-purine as claimed in claim 1. 6. A process for the preparation of 3-((2-amino-9H-purin-9-yl)methoxyj-1,2 propanediol as claimed in claim 1.

Inventors: BEAUCHAMP, LILIA MARIE, KRENITSKY, THOMAS ANTHONY
Applicants: THE WELLCOME FOUNDATION LIMITED
Application year: 1986
Main classification: C07D473
IPC codes: C07D473