NZ217312A - Purine derivatives and pharmaceutical compositions - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £17312 21731 Priority DaleiS1: .^V.~ !^P., k2. «vr.lQ:82 ..Uj.- iO-S2,2&1^.?.

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Cavv-^p jc :r_c.:; ' ' ! •.' rccn anrc-chtdl to 13> Cc.+c4o^- i / £3L •^taicJaU PATENTS ACT, 1953 Divided from No. 205955 No.: Date: COMPLETE SPECIFICATION ANTIVIRAL COMPOUNDS )tyWe> THE WELLCOME FOUNDATION LIMITED, 183-193 Euston Road, London, N.W.I., England, a company incorporated in England, hereby declare the invention for which Ity we pray that a patent may be granted to *it#yus, and the method by which it is to be performed, to be particularly described in and by the following statement:- (followed by la) r o -la- Antiviral Compounda The present invention relates to antiviral purine derivatives containing an acyclic chain in the 9-position.

New Zealand Patent Specification No. 178556 describes a broad class of purine derivatives containing an acyclic side chain in the 9-Dosition. These purine derivatives have been found to have antiviral activity against various classes of DNA viruses particularly against herpes viruses such as herpes simplex.

Among these derivatives, 9-(2-hydraxyethoxymethyl)guanine (otherwise known as acyclovir) has been found to have particularly good activity against herpes viruses such as herpes simplex. However, while acyclovir has been found to be especially effective upon topical or parenteral administration, it is only moderately well absorbed upon oral administration with corresponding levels of drug in the plasma. It will be appreciated that when one is treating an internal disorder by oral administration of a drug, it is clearly desirable that the drug should be well absorbed from the gastro-intestinal tract with resulting high plasma levels.

We have now made the surprising discovery that purine derivatives which are characterised by the presence of a hydrogen atom in the 6- position of the purine nucleus, can be readily converted jn vivo by the action of enzymes of the molybdo-flavo-protein type (especially xanthine oxidase/dehydrogenase or aldehyde oxidase) into the corresponding 6-hydroxy purine derivatives having antiviral activity. Furthermore, from experiments in rats, we have found that oral administration of such 6-hydrogen derivatives results in efficient absorption from the gastra-intestinal tract and high plasma levels of the corresponding 6-hydroxy compound, formed by enzymatic conversion of the 6-hydrogen compound.

The above-mentioned class of 6-hydrogen purine derivatives may be represented by the general formula (wherein X represents an oxygen or sulphur atom) and physiologically acceptable salts ar.d esters thereof (other than the compound of formula (I) wherein X represents an oxygen atom and its physiologically acceptable salts and benzoa^e ester).

Salts of the compounds of formula (I) which may be conveniently used in therapy include physiologically acceptable salts of organic acids such 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 compounds of formula (I) which may be conveniently used in therapy include those containing a formyloxy or (for example C., Jalkanoyloxy (e.g. acetoxy or propionyloxy), optionally substituted aralka-1 *6 noyloxy (e.g. phenyl-C^ ^alkanoyloxy such as phenyl-acetoxy) or optionally substituted aroyloxy (e.g. benzoyloxy or naphthoyloxy) ester grouping at one or both of the terminal positions of Che 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.

The present invention also includes bioprecursors of the compounds of formula (1) and their physiologically acceptable salts and esters, i.e. compounds which are converted in vivo into compounda of formula (I) and their above-mentioned derivatives. 2-Amino—9-(2-benzoyloxyethoxymethyl)purine (i.e. the benzoate ester of the compound of formula (I) wherein X represents an oxygen atom) is disclosed in US Patent Specification No. 4,199,547 and no claim is made herein to this compound per se. However, there is no indication or suggestion in the said US Specification that the compound can be converted in vitro into the corresponding 6-hydroxy analogue. The discussion hereinafter relating to the medical usage and pharmaceutical formulations of compounds of formula (I) ■; . and their physiologically acceptable salts and esters thus includes the said ^j^gnzoate ester. The parent compound formula (I) wherein X represents an oxygen atom and its physiologically acceptable salts are described and claimed 1 ONOV1987i„J New Zealand Patent Specification No. 205955.

The diicovery that the 6-hydrogen purines above can be readily converted into their corresponding 6-hydroxy analogues is surprising since in previous studies with xanthine oxidase from bovine milk (H.Lettre et al (1967) Biochem.Pharmacol., 16, 1747-1755; T.A. Krenitsky et al (1972) Arch. Biophys., 150, 585-599), it was shown that 9- substitution obliterates or greatly diminishes the rate at which a variety of purines are oxidised. In view of these observations, it was surprising to find that this enzyme oxidised for example 6-deoxyacyclovir, a 9-subntituted derivative of 2-aminopurine, at a faster rate than the 9-unsubstituted purine, as we have established from enzyme studies.

The high level of absorption of the compounds of formula (1) from the gastrointestinal tract renders the compounds especially useful when oral administration of the compounds is desired, e.g. in the treatment of diseases caused by various DNA viruses, such as herpes infections for example herpes simplex, varicella or zoster, cytomegalovirus as well as diseases caused by hepatitis B or EpsteirvBarr virus. The compounds of formula (I) can also be used for the treatment or prophylaxis of papilloma or wart virus infections. In addition to their use in human medical therapy the compounds of formula (1) can be administered to other animals for the treatment or prophylaxis of viral diseases, e.g. in other mammals.

By administration of a compound of formula (I) or physiologically acceptable salt or ester thereof, especially by the oral route, it is possible to achieve an advantageous effect agpinst such disorders.

The compounds 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 Co be created and the identity of the recipient and will ultimately be at the discretion of the attendant physician or tfgterinarian. In general however, for each of these utilities and indications, a ■n, "1* * i t: 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 lOOmg per kilogram # body weight per day and most preferably in the range 5 to 20mg per kilogram I bodyweight per day; an optimum dose is about lOmg per kilogram badyweight 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 lOOOmg, preferably 20 to 500mg and most preferably 100 to <t00rng 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 earrieKs) must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof. v i' \ 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 oil— in-water liquid emulsion or a water-in-oil liquid emulsion. The active ingredient may also be presented as a bolus, electuary or paste.

* - A cablet may be made by compression or moulding, optionally with one or more accessory ingredients. Compressed Cablets 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 Cablets 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 che 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. When formulated in an ointment, the active ingredients may be employed with either a paraffinic or a water-misciblo ointment base. Alternatively, the Bctive ingredients may be formulated in a cream with an oil-in-wacer cream base.

If desired, the aqueous phase of the cream base may include, for example, at least 30% w/w of a polyhydric alcohol, i.e. an alcohol having two or more hydroxyl groups such as propylene glycol, butane 1,3-diol, mannitol, sorbitol, glycerol and polyethylene glycol and mixtures Chereof. The topical formulations may desirably include a compound which enhances absorption or penetration of the active ingredient through the skin or other affected areas. Examples of such dermal penetracion enhancers include dimethylsulphoxide and related analogues.

The oily phase of the emulsions of Chis invenCion may be constituted from'known ingredients in a known manner. While the phase may comprise merely an emulsifier (otherwise known as an emulgent), it desirably comprises a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil. Preferably, a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabiliser. It is also preferred to include both an oil and a fat. Together, the emulsifier(s) with or without stabiliserfs) make up the so-called emulsifying wax, and the wax together with the oil and/fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations.

Emulgents and emulsion stabilisers suitable for use in the formulation of the - 'present invention include Tween 60, Span 80, cetostearyl alcohol, myristyl Oh lcohol, glyceryl mono-stearate and sodium lauryl sulphate.

The choice of suitable oils or fata for the formulation is based on achieving the desired cosmetic properties, since the solubility of the active compound in most oils likely to be used in pharmaceutical emulsion formulations is very low. Thus the cream should preferably be a non-greasy, non-staining and washable produce with suitable consistency to avoid leakage from tubes or other containers. Straight or branched chain, mono- or dibasic alkyl esters such as di-isoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palm it ate or a blend of branched chain esters known as Crodamol CAP may be used, the last three being preferred esters. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and/or liquid paraffin or other mineral oils can be used.

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 tho 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% w/w.

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 aid 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 Cy 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 present invention further provides veterinary compositions comprising at least one active ingredient as above defined together with a veterinary carrier therefor.

Veterinary carriers are materials useful for the purpose of administering the composition and may be solid, liquid or gaseous materials which are otherwise inert or acceptable in the veterinary art and are compatible with the active ingredient. These veterinary compositions may be administered orally, parenterally or by any other desired route.

For oral administration the compositions can be in the form of a tablet, granule, drench, paste, cachet, capsule or feed supplement. Granules may be made by the well known techniques of wet granulation, precompression or slugging. They can be administered to animals in an inert liquid vehicle so as to form a drench, or in a suspension with water or oil base. Preferably further accessory ingredients ■v such as a dispensing agent are included. These formulations preferably contain from 15 to 85% of the active ingredient.

A pa3te may be formulated by suspending the active ingredient in a liquid diluent. A stiffening or thickening agent may be included together with a 1 0 NOV 1987 t> // 1 wetting agent or a humectant if the liquid diluent is water. If an emulsion paste is needed then one or more surface active agents should desirably be Included. From 25 to 80% by weight of these paste formulations may comprise the active ingredient.

In feed supplements the active ingredient is generally present in large amounts relative to the accessary ingredients, and the supplements may be added directly or after intermediate blending or dilution. Examples of accessory ingredients for such formulations include solid, orally ingestible carriers such as corn meal, soya flour, wheat shorts, soya grits, edible vegetable materials and fermentation residues. The active ingredient is usually incorporated in one or more of the accessory ingredients and intimately and uniformly dispersed by grinding, tumbling or stirring with conventional apparatus. Formulations containing 1 to 90% by weight of the active ingredient are suitable for adding to feeds.

For the treatment of herpes infections in horses, an oral or parenteral of from 0.1 to 250mg per kg body weight per day, preferably from 2 to lOOmg per kg per day may be required. The dose may be split up into discrete units administered at regular intervals during the day, and repeated daily for up to 14 days or until the infection is cleared. For viral infections in other animals the dose may vary depending on the size and metabolism of the animal. The compositions may be administered in unit "dosage form, such as a tablet a few times daily in the amount of 10 to lOOOmg per unit dose.

The compounds of formula (I) and 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 New Zealand Patent Specification No. 178556.

The present invention provides a process for the preparation of compounds of formula (I) and physiologically acceptable salts and esters thereof (as defined above) which comprises (a) converting a compound of formula M (II) 1 ONOV19* . I ch2 x ch2ch2oh * > » • ' f ' * (wherein X is as defined above, M represents a hydrogen atom or a group or atom convertible info a hydrogen atom and G represents a group or atom convertible into an amino group or (when M is other than a hydrogen atom) G may alternatively represent an amino group) or a salt or ester thereof into a compound of formula (I) or a physiologically acceptable salt or ester thereof; » ) reacting a compound of formula O <3 (wherein Q represents a leaving atom or group) with a compound of formula ACH 2 X CH2CH2B (IV) (wherein X is as defined above, A represents a leaving group or atom and B represents an optionally protected hydroxy group); c) closing a ring in a precursor compound having either the pyrimidine or imidazole ring incompletely formed; d) converting a compound of formula CH X CH2CH2NH2 (V) \ < 10HOVl98?;r! v-/v e 0 S ' 1 ' t; (therein X is as defined above) into a corresponding compound of formula (I) or a physiologically acceptable salt or ester thereof; and optionally effecting one or more of the following conversions, in any desired sequence:' where the resulting product is a base,..converting the said base into a physiologically acceptable acid addition salt thereof; where the resulting product is an acid additon salt, converting the said salt into the parent base; where the resulting product is a 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/or where the resulting product is an ester of a 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. i> O ii) ni) iv) Conversion of a compound of formula (II) into a compound of formula (I) by method a) 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 atom or an alkylthio or alkylsulphonyl group which can be converted to an amino group by aminolysis using for example ammonia. M may represent a halogen e.g. chlorine, atom or a mercapto or thio (S <) group which c \ IJ°«0Vl987i \ -n / / v * t\- // I o can be converted into a hydrogen atom in conventional manner. In the case where M represents a thio qroup, this conversion may be effected using a compound of formula ill) m which any amino or hydroxyl groups are optionally blocked by acyl groups, the conversion being effected using a Raney nickel catalyst, e.g in a basic medium which additionally removes the amino and/or hydroxy blocking groups.

These processes together with other conventional processes are described in Fused Pyrimidines, Part II, Purines Ed. by D. J. Brown (1971), Wiley-Interscience. 'w In process (b) the group Q in formula (IllVnay for example represent a hydrogen atom; an acyl group, e.g. a ^alkanoyl group such as an acetyl group or an aroyl group such as a benzoyl group; or a tri-C^_^alkylsilyl group such as a trimethylsilyl group. The group A in formula (iv)nay for example represent a "halbgeh~arom~fe:gv chlorine) or an acyloxy group wherein the acyl moiety may be for example a C^^alkanoyl group such as acetyl, or an aroyl group such as benzoyl. The reaction may be conveniently effected in a strong polar solvent such as dimethylformamide 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 (m jand (IVjn the presence of a catalytic amount of a strong acid, e.g. sulphuric acid.

Process c) involves the ring closure of either the imidazole or pyrinudine ring to give the final product. In the case of the imidazole ring this may be achieved by reaction of an appropriate percursor with t triethylorthoformate, under for example mildly temperature of about ?5°C, for several hours, substituted pyrimidine of formula* reagent, such as acidic conditions, at a A suitable precursor is CH-XCHCH.OH i n. 2 v Y °~\ An alternative reagent is diethoxymethyl acetate, when neutral conditions at about 100°C for about 10-15 minutes are preferred. r .r-W*®- i n ; ' <; In process d) the conversion is advantageously effected by treatment of the amino compound of formula (v) with a nitrite, e.g. sodium nitrite, in an acidic medium.

The starting materials employed in the processes described above may be prepared in conventional manner, e.g. in accordance with the processes described in the above-mentioned New Patent Specification No* 170556.

The following Examples illustrate the present invention Example 1 2-Amino-9-(2-hydroxye thy 1thiomethy1*-9H-purinc A 1 litre round bottom flask equipped with a magnetic stirring bar and a CaCl^ drying tube was charged with 5.0g (29.50mM) 2-amino-^-chloro-p urine, 6.8g (29.50mM) 2-(chloromethylt!iio)ethyl benzoate, 4.07g (29.50mM) potassium carbonate and 750ml of anhydrous dimethyl formamide. The reaction was stirred at room temperature for 16 hours after which time another 2.0g (8.7mM) of 2-(chloromethylthio)ethyl benzoate with 1.2g (8.7mM) potassium carbonate were added and stirring continued for an additional 24 hours at room temperature. The reaction mixture was then filtered through a pad of Celite in a sintered glass funnel and rotary evaporated in vacuo to a viscous yellow oil.

The oil was adsorbed on to 20.0g of Merck silica gel 60 (70-230 mesh) and this preadsorbed phase applied to the top of a column of Merck silica gel 60 (230-400 mesh). Elution of the column using 6:4 ethyl acetate-benzene provided 2-amino-9-(2-benzoyloxyethylthiomethyl)-6-chloro-9H-purine as an off-white solid as a single material by TLC on silica gel 8:2 ethyl acetate-hexane. *H NMR, CDCl^ 8.0-7.15, 6H, multiplet; 5.1, 4H, broad singlet; 4.5, 2H, triplet 2-985, 2H triplet.

The last-mentioned product (Q.98g 2.70mM) was placed into a 500ml Parr hydrogenator bottle together with 2.5g Pd (OH^ catalyst, 50ml triethylamine arid 200ml of methanol. This was shaken in a Parr hydrogenator under 50 p-s.i. hydrogen for 16 hours at room temperature. TLC of the hydogenolysis product on silica gel with 8% methanol - ethyl acetate showed only partial reaction- The catalyst was removed by filtration through a pad of Celite in a sintered glass funnel, 2.0g of fresh PtftOH^ catalyst and 7.0ml triethylamine were added and • • S\ the reaction mixture again shaken under 50 p.s.i. hydrogen (or 20 hours. At this point t.I.c showed the reaction to be complete, the catalyst was removed as before and the methanol removed by rotary evaporation in vacuo to give a clear glass, which was taken up into 100ml of 1:1 methanol-water containing 20% methylamine. The resulting solution was stirred at room temperature for 4 hours and removed by rotary evaporation in vacuo to give an amorphous solid. The solid was adsorbed on co lO.Og of 70-230 mesh Merck silica gel £0 and this preadsorbed phase applied to the top of a column of 230-400 mesh Merck silica gel 60. Elution of the column using 10% methanol ethyl acetate provided a solid that cyrstallised from ethyl acetate-hexane to give the title compound in the form of needles, m.p. 122-124°C, t.l.c.: 1 spot on silica gel with 15% methanohethyl acetate, "H NMR dmso-d6 8.59, 1H singlet; 8.15, 1H singlet; 6.56, 2H broad singlet; 5.24, 2H singlet; 4.83, 1H triplet; 3.49, 2H multiplet; 2^9, 2H, *~" multiplet; Anal. Theory C: 42.65 H4.92, N: 31.09 found C: 42.70,H: 4.94, N: 31.04. cli - 1 Example 2 9-(2-Acetoxyethoxymethyl)-2-amino-9H-t>urine A mixture of 0.82g (3.92mM) of 9-(2-hydroxyethaxyrnethyt)-2-«mino-9H-purirwl 48mg (0.392mM) of 4-dimethylaminopyridine and 0.75ml (7.84mM) of acetic my anhydride in 18ml of dry dimethylformamide was stirred at room temperature for two days.

The reaction mixture was evaporated in vacuo and the residue dissolved in ethyl acetate and absorbed on silica gel. The solvent was removed by flash evaporation and the residual powder added to a column prepared for flash chromatography. Elution with 5% methanol in dichloromethane gave l.Og of a semicry3talline oil which on recrystallization from benzene-hexane gave analytically pure 9-(2-acetoxyethoxymethyl)-2-amino-9H-purine, mpt=115-118°C. ftanple 3 9-(2-Acetoxyethylthiomethyl)-2-amino-9H-purine A 100ml flask equipped with a magnetic stirring bar and a CaCIj drying tube was charged with l.Og (4.4mM) 2-amino-9-(2-hydroxyethylthiomethyl)-9H-purlnBf 0.054g (0.44mM) 4-dimethylaminopyridine, 0.9ml (8.8mM) acetic anhydride, and 20ml of dry DMF. The solution was stirred for 24 hours at room temperature and t.'ien quenched with 5ml of MeCH. Tha solution was evaporated In vaciM (bach temp 40°C) and the brown oil -o obtained chramato graphed using Che "flash" method. Elution of the column with 1.5% methanol in ethyl acetate provided a yellow oil which crystallizad on standing. The light yellow crystal* ware dissolved in a solution of 2% MeCH in touene and treated with QJ)5g Darco G-60.

The methanol was evaporated from the toluene solution resulting in the precipitation of light yellow crystals.

The product was dried for lo houm at 78°C ta yield the title compound mp =119-120.5°C. Anal. Calcd. for C^qH^N^Q^S: C, 44.93; H, 4.9: N, 26.20. Found: C.44.97, H, 4.96; N, 26.17. XH NMR in*DMS06 8.59 (1HS), 8.15 ClHs), 6.52 (2H broad 3) 5.26 (2Hs), 4.15 (2Ht J = 6.36 Hz), 2.89 (2Ht J = 6.36 Hz), 1.99 (JHs).

Exaaple 4 2-Amino-9-(2-benzovloxyethvl:hiornethyl)-9H-purine A 5- litre, 3-neck flask was equipped with an air-stirring motor, glass stirring rod with teflon paddle, and provision made for evacuating and filling the flask with either or gas. The flask was then charged with 7.Q g (0J)19 M) of 2-amina-9-(2-benzoyloxyethylthiomethyl)-6-chloro-9H-purine, 14.0 g palladium hydroxide on carbon, 12.0 ml (0.163 M) triethylamine, 75.0 ml water and 3.0 litres of methanol. The flask waa then sealed and evacuated using a water aspirater, flooded with Nj gas, evacuated until 3 complete cycles 'were completed. The flask was evacuated, flooded with H^ gas, evacuated and refilled with gas. The stirring motor was started and the reaction was stirred under for 4 days at room temperature.

The solution was filtered through a sintered glass funnel and the catalyst washed with 800 ml of methanol. The methanol solution was evaporated in vacuo to give 6.0 g of a light yellow solid. The solid was absorbed onto 18.0 g of 70-230 mesh silica gel 60 and this preabsorbed phase applied to the top of a column of 230-400 mesh silica gel 60. Elution of the column by the "Flash" method using'5% • methanol in ethyl acetate provided a whits solid which was racrystallized from •" ethyl acetate-hexane, dried at 78°C under 1.0 mm Hg vacuum to white flakes mp ~ 120-121°C, H NMR in dmso d& 8.60 (1 H,s), 8.19 (1 hU), 8.0 7.5 (5 H/n), 6^55 <2 H,s) 5.32 (2 H,a), 4.52 (2 H, t), 3.06 (2 H, t) Anal, theory C: 54^9, Hi 4^9 N: • 21.26 Anal, found C: 54.68, Hs 4.64, Ns 21.24 ; ? 2-Amino-9-(2-hydaxyethylthiomethyl)-9H-purine was oabtairted by continued elution of che above column.

The following Examples, 5 to 3 illustrate pharmaceutical formulation according to the invention where the active compound is a compound of focrnula (I) or a physiologically acceptafcie salt or escer thereof.

EmnoifA Tablet Active compound 200mg Lactose 23Smg Starch 50 mg Polyvinylpyrrolidone 50 mg Magnesium stearate 5mg 500mg Mix the active compound with che lactose and starch and wet .granulate with a solution of the polyvinylpyrrolidone. Dry, sift, blend Che granules with magnesium stearate and compress.

Example6 Capsule AcCive compound 200mg Lactose 184mg Sodium starch glycollaCe 8mg Polyvinylpyrrolidone 6mg Magnesium stearate Zmg Mix Che active compound with Che lactose and sodium starch glycollaCe and wet granulate with a solution of the polyvinylpyrrolidone. Dry, sift, blend theV.:'; granules with the magnesium'stearate and fill into hard gelatin capsules. . . .'v •

Claims (2)

E-tampla7 Cream Active compound 5.00g Glycerol 2.C0g Cetostearyl alcohol 6.75g Sodium lauryl sulphate 0.75g White soft paraffin * 12.50g Liquid paraffin S.OOg Chlorocresol 0.10g Purified water to 100.OOg .r r.Vr"'. Dissolve the active compound in a mixture of purified water and glycerol and heat to 70°C. Heat the remaining ingredients together at 70°C. Add the two parts together and emulsify. Cool and fill into containers. Example 8 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 che ampoules. 8) Active compound lOOmg 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 wich 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 aluminium collar. -G" i'-o .: -17- WHAT WK CLAIM 15:

1. Compounds cf the general formula O h2-N (I) 0Ho X CH^CH^OH (wherein X rppr-?s<*t.tr; an oxygen or sulphur atom) and physiologically acceptable salts and esters thereof (other than the compound of formula ([) wherr-in X represents an oxygen atom and it3 physiologically acceptable salts and benzoate ester).

2. 2-Amino-9-(2-hydr .xyethylthiomethy1)-9H-purine. 9-(2-Acetoxyethoxymethyl)-2-amino-9H-purine. 2-Amino-9-(2-benzoyloxyethy1thiomethyl)-9H-purine. A process for the preparation of compounds of formula (I) and physiologically acceptable salts and esters thereof as claimed in claim 1 which comprises a) converting a compound of formula (II) CH2 X CH2CH20H (wherein X is as defined in claim 1, M represents a hydrogen atom or a group or atom convertible into a hydrogen atom and G represents a group or atom convertible into an amino group or (when M is other than a hydrogen atom) G may alternatively represent an amino group) or a salt or ester thereof, into a compound of formula (I) or a physiologically acceptable salt or ester thereof; b) reacting a compound of formula N' h2N (III) I -18- (wherein Q represents a leaving atcn or group) with a compound of formula ACH2 X CH2CH2B (IV) (wherein X is as defined in claim 1, and A represents a leaving group or atom and B represents an optionally protected hydroxy group); c) closing a ring in a precursor compound having either the pyrimidine or imidazole ring incompletely formed; d) converting a compound of formula N (V) h2N CH2 X CH2CH2NH2 (•^herein X is as defined above) into a corresponding compound of formula or a physiologically acceptable salt or ester thereof; ar.i optionally effecting ore or more of the following conversions, L:\ ... desired sequence :- i) where Che 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 :he said salt into the parent base; iii) where the resulting product is a 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/or _ . - r "^iv) where the resulting product is an ester of a compound of formula U) converting the said ester into the parent compound of formula (I), a physiologically acceptable salt thereof or a different physiologically ^ if acceptable ester thereof! — r t Pharmaceutical formuLations comprising at least one compound as claimed in any one of drums 1 to A (additionally including the benzoate ester of the compound r>f formula tl) wherein X represents an oxygen atom), together with one or more pharmaceutical^ acceptable carriers therefor. Compounds as claimed in any one of claims 1 to A for use in the treatment or prophylaxis of a viral disease in an animal. "a™ j ^PAoAV0F,sb^^i»^ ^HK & sON *ZR AbfcMTSFOq n-.CAPPL^wm