CS244696B2 - Production method of 2-amino-9/(2-hydroxyethoxymethyl)-9h-purine - Google Patents

Abstract

Cpds. of formula (I) and their physiologically acceptable salts and esters are new (where X is O, S or a bond; R' is halogen, amino or azido; R2 is H, OH, alkyl or hydroxyalkyl; R3 is H or alkyl; R4 is OH, hydroxyalkyl, benzyloxy, phosphate or carboxypropionyloxy; and R5 is H, alkyl or hydroxyalkyl). 3 cpds. are specifically claimed, e.g. 2-amino-9-(2-hydroxyethoxymethyl) -9H-purine. (I) are antiviral agents having a high level of absorption from the g.i. track. They are useful in treatment of diseases caused by e.g. herpes simplex, -raricella or -zoster, cytomegalovirus, ehpatitis B virus or Epstein-Barr virus. They may also be used for treatment or prophylaxis of papilloma or wart virus infections, and for treatment of equine rhinopneumonitis. Doses are 0.1-250, esp. 5-20 mg/kg/day, e.g. in units contg. 100-400 mg of active agent. Admin. may be enterally, parenterally or topically.

Description

The present invention relates to antiviral purine derivatives containing an acyclic chain at the 9-position.

British Patent No. 1,523,865 discloses a series of purine derivatives having an acyclic side chain at the 9-position. These purine derivatives have been found to have antiviral activity against various classes of DNA viruses, particularly herpes viruses such as Herpes simplex.

Among these derivatives, a particularly good effect against herpes viruses such as Herpes simplex has been found with 9- (2-hydroxyethoxymethyl) guanine (commonly referred to as acyclovir). However, while acyclovir has been found to be particularly effective against viruses when administered topically or parenterally, it is only moderately absorbed when administered orally at appropriate plasma levels of the drug. It is clear that in the treatment of internal disorders by oral drug administration, it is desirable that the drug be well absorbed from the gastrointestinal tract and achieve high plasma levels.

It has now surprisingly been found that a purine derivative characterized by the presence of a hydrogen atom at the 6-position of the purine nucleus, namely 6-deoxyacyclovir, i.e. 2-amino-9- (2-hydroxyethoxymethyl) purine, a 6-hydrogenated acyclovir analog, may be easily converted in vivo by the action of molybdo-flavoprotein type enzymes (particularly xanthine oxidase / dehydrogenase or aldehyde oxidase) to the corresponding 6-hydroxypurine derivatives having antiviral activity. In addition, experiments in rats have shown that oral administration of such a 6-hydrogenated derivative results in efficient absorption from the gastrointestinal tract and high levels of the corresponding 6-hydroxy compound in plasma, which compound is formed by enzymatic conversion of the 6-hydrogenated compound. Also, for example, 6-deoxy-acyclovir is much more soluble in water nežacyklovir wherein 6-deoxy-acyclovir exhibits a solubility of 50 mg / MR c zaHmco ^YKL r ⁱ s ^{1, 2,} 3 mg / m ^{L at} 5 ° C. This of e ^{l p p} Sena extended ustnos ^t in water enhanced by the use of 6-deoxy-acyclovir in a plurality of aqueous pharmaceutical formulations which require a solubility of the drug.

The above 6-hydrogenpurin derivative is represented by the formula I

CH ₂ -O-CH ₂ -CH ₂ -OH and its physiologically tolerable salts. Salts of a compound of formula I which can usually be used for therapeutic purposes include physiologically tolerable salts of organic acids such as lactic acid, acetic acid, malic acid or p-toluenesulfonic acid and physiologically tolerable salts of mineral acids such as hydrochloric acid or sulfuric acid .

The finding that 6-hydrogenpurine can easily be converted to its corresponding 6-hydroxy analog is surprising since in previous studies and with cow's milk xanthine oxidase / Hilettre et al., Biochem. Pharmacol., 1767-1755 (1967); T. A. Krenitsky et al.,

Sheet. Biophys., 150, 585-599 (1972)], it has been found that the 9-substitution attenuates or greatly reduces the rate at which various purines are oxidized. In view of these observations, it was surprising to find that this enzyme oxidized more rapidly, for example, 6-deoxyacyclovir, a 9-substituted 2-aminopurine derivative, than a 9-unsubstituted purine, as found in enzymatic studies.

The high absorption value of the compound of formula I from the gastro-Snbivial tract is particularly advantageous in the oral administration of this compound, for example in the treatment of diseases caused by various DNA viruses such as herpes infections such as Herpes simplex, varicella or zoster, cytomegalovirus, as well as Epstein-Barr virus.

The compound of formula I can also be used for the treatment or prophylaxis of papilloma or wart virus infection. In addition to its use in human medicine, the compound of formula I may be administered to animals, for example mammals, in the treatment or prophylaxis of viral diseases.

The invention further relates to a compound of formula I and their physiologically tolerable salts for use in the treatment or prophylaxis of viral diseases in animals, for example mammals, such as humans.

The invention also relates to a method for the treatment or prophylaxis of viral diseases in animals, for example mammals, such as humans, comprising administering to the patient an effective amount of a compound of formula I or a physiologically tolerable salt thereof.

The compound of formula I and its physiologically tolerable salts (hereinafter referred to as the active ingredients) may be administered by any route suitable for the method of treatment, including oral, rectal, massal, topical (including buccal and siblivgial), vaginal and the parenteral (including ucutaneous, intramuscular, intravascular, intradermal, intrathecal, and epidural) routes. Obviously, a suitable method will be guided, for example, by the condition of the recipient.

The amount of active ingredient required for each of the above methods and indications depends on many factors, including the pain of the condition being treated and the individual recipient, and ultimately depends entirely on the judgment of the attending physician or veterinarian. In general, however, for each of these uses and indications, an effective dose is in the range of 0.1 to 250 mg per kilogram of recipient body weight per day, preferably in the range of 1 to 10 mg per kilogram. body weight per day, and in particular in the range of 5 to 20 mg per kilogram body weight per day.

The optimum dose is about 10 mg per kilogram of body weight per day. (Unless otherwise indicated, all weights of active ingredient are recalculated to the compound of Formula I. As such, for salts of this compound the values are proportionally increased). The desired dose is preferably administered in two, three, four or more sub-doses administered at appropriate intervals throughout the day. These sub-doses may be administered in the form of dosage units, for example, containing 10 to 1000 mg. preferably 20 to 20 substances per dosage unit.

500 mg, and most preferably 100 to 400 mg, is better to be administered in the form of a pharmaceutical-pharmaceutical use according to the invention

Although it is possible to administer the active ingredient alone, the compositions may be administered. Compositions for both veterinary and at least one active ingredient, together with one or, if desired, other therapeutic ingredients. The carrier or carriers must be compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

The compositions include forms suitable for oral, rectal, massal, topical (including subcutaneous, intramuscular and intravenous, intradermal, intrathecal, and epidural) administration. The compositions may conveniently be presented in unit dosage form and may be prepared by methods well known in the art of pharmacy. Such methods include the step of mixing the active ingredient with a carrier which comprises one or more accessory ingredients. In general, the compositions are prepared by homogeneously intimately mixing the active ingredient with liquid carriers or finely divided solid carriers and optionally shaping the product.

Compositions of the invention suitable for oral administration may be in unit dosage form, for example, capsules, cachets or tablets each containing a specified amount of the active ingredient, such as a powder or granules, as a solution or suspension in an aqueous or non-aqueous liquid. or as an oil-in-water or water-in-oil emulsion. The active ingredient may also be presented in the form of a large soft pill, potion or paste.

Tablets may be made by compression or molding, as appropriate, together with one or more accessory ingredients. Compressed tablets may be compressed in a suitable machine from the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, preservative and surface-active or dispersing agent. Molded tablets may be prepared in a suitable machine by casting a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may advantageously be coated or scored and formulated to provide the active ingredients.

slow or controlled release or skin, with the effectiveness of the additive in amounts

In the case of infection of the eyes or other external tissues, for example the mouth, they are preferably applied as topical ointments or creams which contain, for example, 0.075 to 20% by weight, preferably 0.2 to 15% by weight and most preferably 0.5 to 10% by weight. When used in an ointment, the active compounds can be used either with a paraffinic base or with a water-miscible ointment base. Alternatively, the active ingredients may be formulated in a cream with an oil-in-water cream base.

If desired, the aqueous phase of the cream base may contain, for example, 30% by weight of a polyhydric alcohol, i.e., an alcohol having two or more hydroxy groups such as propylene glycol, 1,3-butanediol, mannitol, sorbitol, glycerol and poylethylene glycol and mixtures thereof. Topical formulations may, if desired, contain a compound which facilitates the absorption or penetration of the active ingredient into the skin or other affected area. Examples of such skin penetration agents are dimethylsulfoxide and analogs thereof.

The oily phase of the emulsions of the invention may be constituted by known ingredients and may be prepared in a known manner. While this phase may comprise a mere emulsifier (otherwise referred to as an emulsifier), it is preferred that it comprises a mixture of at least one emulsifier with a fat or an oil or both a fat and an oil.

Preferably, a hydrophilic emulsifier is used together with a lipophilic emulsifier which acts as a stabilizer. It is also preferred that this phase contain both oil and fat. Emulsifier or emulsifiers with or without a stabilizer or stabilizers form a so-called emulsifying wax. This wax together with the oil and / or fat forms a so-called emulsifying ointment base which forms the oil dispersed phase of the cream compositions. *

Emulsifiers and emulsion stabilizers suitable for use in the compositions of the invention include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate and sodium lauryl sulfate.

The choice of suitable oils or fats for the compositions is governed by the desired cosmetic properties since the solubility of the active compound in most of the oils contemplated for use in pharmaceutical compositions is very low. The cream should preferably be non-greasy and spotless and should be washable with a suitable consistency to prevent leakage from tubes or other containers. It is possible to use straight or branched mono- or dialkyl esters such as diisoadipate, isocetyl stearate, coconut fatty acid propylene glycol ester, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a mixture of branched esters known as Crodamol. The three latter esters are preferred. These may be used alone or in admixture depending on the desired properties of the product. Alternatively, high melting point lipids may be used as well. and white soft paraffin and / or liquid paraffin or other mineral oils.

Compositions suitable for topical administration to the eye also include eye drops in which the active ingredient is dissolved or suspended in a suitable carrier, especially an aqueous solution. the active ingredient. Such compositions preferably contain the active ingredient in a concentration of 0.5 to 20% by weight, preferably 0.5 to 10% by weight and in particular about 1.5% by weight.

Formulations suitable for topical administration in the mouth include drinkable sauces, usually sucrose and acacia or tragacanth. The lozenges contain the active ingredient in an inert base such as gelatin or glycerin or sucrose and acacia. Mouthwashes contain the active ingredient in a suitable liquid carrier.

The compositions for rectal administration may be in the form of suppositories with a suitable base comprising, for example, coconut butter or salixylate.

Formulations suitable for nasal administration in which the carrier is in the form of a solid include coarse powders having a particle size of, for example, 20-500 microns, which are administered by snuffing, i.e. by rapid inhalation through the nasal channel from a powder reservoir held near the nose. Suitable compositions in which the carrier is a liquid, for administration in the form of, for example, a nasal spray or nasal drops, include aqueous or oily solutions of the active ingredient.

Compositions suitable for vaginal administration may be in the form of pessaries, tampons, creams, jellies, pastes, foams or sprays containing in addition to the active ingredient carriers which are known in the art to be appropriate. ‘

Compositions suitable for parenteral administration include aqueous and non-aqueous sterile injectable solutions which may contain antioxidants, buffers, bacteriostats and solutants that improve the ionic relationship of the composition to the blood of the recipient, and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickeners.

The compositions may be stored in disposable or multidose containers, for example, sealed ampoules and vials, and may be stored in a lyophilized state, and prepared just prior to use by simply adding a sterile liquid carrier, such as water for injection. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described. Preferred unit dosage formulations comprise a daily dose or unit daily sub-dose of the active ingredient, as mentioned above, or a suitable fraction thereof.

It is to be understood that in addition to the ingredients individually listed above, the compositions of the invention may contain other ingredients conventional in the art with respect to the type of composition concerned. E.g. the composition for oral administration may contain flavoring agents.

The invention further relates to veterinary compositions comprising at least one active ingredient mentioned above together with a suitable veterinary carrier.

Veterinary carriers are substances suitable for the purpose of administering the composition and may be in the form of solid, liquid or gaseous materials which are otherwise inert or veterinary compatible and miscible with the active substance. The veterinary compositions may be administered orally, parenterally, or by any other appropriate means.

For oral administration, the compositions may be in the form of tablets, granules, wettable solutions. flow, wafer with a special cap, capsule or feed supplement. Granules can be prepared by known wet granulation, pre-compression or chopping procedures. The animals may be administered in an inert liquid vehicle in the form of a wetting solution or in suspension with an aqueous or oily base. Preferably, an additional component such as a dispersant is used. Such compositions preferably contain from 15 to 85% by weight of active ingredient.

The paste may be prepared by suspending the active ingredient in a liquid diluent. The densification or thickening agent may be used together with a humectant or wetting agent if the liquid diluent is water. In preparing the emulsion paste, one or more surfactants are suitable. The active ingredient in these paste compositions may comprise 25 to 80% by weight.

In feed supplements, the active ingredient is generally present in larger amounts relative to the constituents and these feed supplements may be administered directly or after mixing or dilution. Examples of additional ingredients for such compositions are, for example, solid, orally administrable carriers such as corn flour, soy flour, wheat feed flour, soybean, edible vegetable materials and fermentation residues. The active ingredient is usually contained in one or more accessory ingredients and thoroughly and uniformly dispersed by crushing, tumbling or mixing in conventional equipment. Compositions containing 1 to 90% by weight of the active ingredient are suitable for incorporation into feed.

For the treatment of Herpes virus infections in horses, an oral or parenteral dose of 0.1 to 250 mg per kilogram of body weight per day, preferably from 2 to 100 mg per kilogram per day, may be suitable. This dose may be divided into subdoses administered at regular intervals throughout the day and repeated for 14 days or until the infection has resolved. For viral infections in other animals, the dose depends on the size of the animal and its metabolism. The compositions may be administered in the form of dosage units, such as tablets, several times a day, the content of active ingredient being 10 to 1000 mg per dosage unit.

The compounds of formula I and their physiologically tolerable salts may be prepared by processes described for the preparation of compounds of similar structure, for example, as described in British Patent No. 1,523,865.

SUMMARY OF THE INVENTION The present invention provides a process for the preparation of a compound of formula (I) and physiologically tolerable salts thereof, comprising:

СН ₂ ОСН ₂ СН ₂ ОН Where

Vod represents a hydrogen atom or a halogen atom or a mercapto group; and

G is acylamido or when M is other than hydrogen, G optionally is amino, or a salt or ester thereof hydrolyses or hydrogenolyses to a compound of formula I or a physiologically tolerable salt or ester thereof, and at least one of the following conversions is carried out as desired order:

(I) if the resulting product is a base, the base is converted into a physiologically tolerable acid addition salt;

(II) where the resulting product is an acid addition salt, the base salt shall be converted;

III) when the resulting product is an ester of a compound of formula I, the ester is converted to the parent compound of formula I or a physiologically tolerable salt thereof.

Conversion of a compound of formula II to a compound of formula I is accomplished by a variety of methods known in the art.

When M is a halogen atom, such as a chlorine atom, or is a mercapto group, their conversion to a hydrogen atom in the resulting compound of formula I may be carried out in a conventional manner.

In one embodiment of the process of the invention, the starting compound is a general compound. of formula II, in which the amino group is protected by an acyl group, is subjected to hydrogenation using Raney nickel catalyst. For example, the reaction is carried out in a basic medium, additionally removing the amino protecting group.

Methods useful in the process of this invention are described in more detail in Fused Pyrimidines, Part II, Purines, published by D. J. Brown (1971), Wiley-Interscience.

Esters of the compound of formula (I) include esters of a compound containing a C 1 -C 16 -alkyloxy or C 1 -C 16 -alkanoyloxy group, for example C 1 -C 6, for example acetoxy or propionyloxy, optionally substituted arylalkanoyloxy, for example C 1 -C 4 phenylalkanoyloxy, in the alkanoyl moiety; or optionally substituted aroyloxy, for example benzoyl-, oxycupine or naphthoyloxy at one or two end positions 9 of the side chain of the compounds of formula I.

The aforementioned aralkanoyloxy and aroyloxy groups of the ester may be substituted, for example, by one or more halogen atoms, for example chlorine or bromine, or by an amino, nitrole or sulfamide group, the aryl part of the group preferably having 6 to 10 carbon atoms.

The starting compounds used in the above process may be prepared in a conventional manner, for example according to the method described in the aforementioned British Patent No. 1,523,865.

The following examples serve to illustrate the invention.

Example 1

A process for the preparation of 2-amino-9- (2-hydroxyethoxymethyl) -9H-purine

A mixture of 2.48 g (7.13 mmol) of 2-amino-6-chloro-9- (2-benzoyloxyethoxymethyl) purine, 250 ml of absolute ethanol, 1.9 ml of triethylamine and 0.6 g of 5% palladium on charcoal was added. shake under an atmosphere of hydrogen at an initial pressure of 34 kPa at a room temperature for 20 hours. The mixture is filtered, 0.265 g of fresh palladium catalyst and 1.9 ml of triethylamine are added and the mixture is shaken under a hydrogen atmosphere for a further 16 hours. The ethanol solution is, after filtration through a pad of Celite, evaporated in vacuo and the resulting white solid extracted several times with boiling benzene. The benzene extracts are evaporated, mixed with 20 ml of 40% aqueous methylamine and 20 ml of methanol and allowed to evaporate to dryness in an open flask on a steam bath. The resulting mixture was triturated with ether to remove N-methylbenzamide and then recrystallized from 100% ethanol to give 2-amino-9- (2-hydroxyethoxymethyl) -9H-purine as analytically pure white granules, m.p. 186-187 °. C.

Example 2

a) A process for the preparation of 2-acetamido-9-acetyl-6-mercapto-9H-purine

A mixture of 54.0 g of thioguanine, 250 ml of acetic anhydride and 2.0 g of p-toluenesulfonic acid was heated at reflux overnight. The reaction mixture was cooled and the solid obtained was filtered off and washed thoroughly with acetone. 62.3 g of 2-acetamido-9-acetyl-6-mercapto-9H-purine are obtained as a brown solid. The NMR spectrum was consistent with the proposed structure.

b) Process for the preparation of 2-acetamido-9- (2-acetoxyethoxymethyl) -6-mercapto-9H-purine

To a mixture of 30.0 g of 2-acetamido-9-acetyl-6-mercapto-9H-purine and 2.0 g of p-toluic acid in 150 ml of toluene is added dropwise over 4 hours at a temperature of 90 to 95 ° C. 0 g of 2-oxa-1,4-butanediol diacetate. After 10 hours, the reaction mixture was cooled and the resulting solid was removed by filtration and washed with acetone. Recrystallization from a 1: 1 mixture of dimethylformamide and acetonitrile and decolourisation with activated carbon gave 25.6 g of 2-acetamido-9- (2-acetoxyethoxymethyl) -6-mercapto-9H-purine as a yellow solid. 205 DEG-206 DEG.

c) A process for the preparation of 2-amino-9- (2-hydroxyethoxymethyl) -9H-purine

0.50 g (1.53 mmol) of 2-acetamido-9- (2-acetoxyethoxymethyl) -6-mercapto-9H-purine, 2 g of freshly prepared W-2 Raney nickel and 25 ml of 58% ammonium hydroxide are heated to reflux. cooler for 2 hours. The catalyst was filtered off and the filtrate was evaporated to a volume of 5 ml. Acetone (20 ml) was then added and the resulting precipitate was filtered and dried to give 0.21 g (65%) of a white solid, mp 188-189 ° C. The product is identical to an authentic sample according to thin layer chromatography and NMR analysis.

Claims (2)

A process for the preparation of 2-amino-9- (2-hydroxyethoxymethyl) -9H-purine of formula I (I) and physiologically tolerable salts thereof, characterized in that the compound of formula II (II) wherein: M represents a hydrogen atom, a halogen atom or a mercapto group; G is acylamido or, when M is other than hydrogen, C optionally represents amino, or a salt or ester thereof, is hydrolysed or hydrogenolyzed to a compound of formula I or a physiologically tolerable salt or ester thereof, and one or more of the following is carried out as appropriate conversions in any order. (I) where the resulting product is a base, the base is converted into a physiologically tolerable acid addition salt, (Ii) where the resulting product is an acid addition salt, the base addition salt is converted; III) when the resulting product is an ester of a compound of formula I, the ester is converted to the parent compound of formula I or a physiologically tolerable salt thereof. 2. The process of claim 1 wherein the compound of formula (II) wherein M is halogen and G is as defined in (1) is subjected to hydrogenation in the presence of palladium catalyst.