CS244679B2 - Production method of anti virus effective compound - 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, 9- (2-hydroxyethoxymethyl) guanine (commonly referred to as acyclovir) has been found to be particularly effective against herpes viruses such as herpes simplex. 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 corresponding plasma drug levels. It is clear that when treating 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-deoxyacyclines, i.e. 2-amino-9- (2-hydroxyethoxymethyl) purine, a 6-hydrogenated acyclovir analogue readily 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 of the gastrointestinal tract and high levels of the corresponding 6-hydroxy compound in plasma, which compound is formed by enzymatic conversion of the 6-hydrogen compound.

Also, for example, 6-deoxyacyclovir is much more soluble in water than acyclovir, with 6-deoxyacyclovir having a solubility of 50 mg / ml while acyclovir 1.23 mg / ml at 25 ° C. This improved water solubility allows the use of 6-deoxyacyclovir in a number of aqueous pharmaceutical compositions which require some solubility of the active ingredient.

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

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 compatible salts of mineral acids such as hydrochloric acid or sulfuric acid .

The discovery that 6-hydrogenpurine can easily be converted to its corresponding 6-hydroxy analog is surprising, as in previous studies with cow's milk xanthine oxidase / Hilettre et al., Biochem. Pharmacol., 16, 1747-1755 (1967); T. A. Krenitsky et al., Arch. Biophys., 150, 585-599 (1972)], it has been shown 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 of the compound of formula I from the gastrointestinal tract is particularly advantageous when administered orally, for example in the treatment of diseases caused by various DNA viruses such as herpes infections such as herpes simplex, varicella or zoester, cytomegalovirus as well as diseases caused by hepatide B; 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 physiologically tolerable salts thereof 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 an antiviral effective amount of a compound of formula I or a physiologically tolerable salt thereof.

The compounds of formula (I) and physiologically tolerable salts thereof (hereinafter referred to as active ingredients) may be administered by any route suitable for the method of treatment including oral, rectal, nasal, topical (including buccal and sublingual), vaginal and parenteral (including subcutaneous, intramuscular, intravenous, intradermal, intrathecal, and epidural) routes. It will be appreciated that a suitable method will follow, for example, the condition of the recipient.

The amount of active ingredient required for each of the above uses 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 body weight of the recipient per day, preferably in the range of 1 to 100 mg per kilogram body weight per day, and particularly in the range of 5 to 250 mg. 20 mg per kilogram of body weight per day.

dosages, administered at appropriate intervals in dosage unit form, for example mg and most preferably 100 to 400 mg of the active ingredient

The optimal 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 increase proportionally). The desired dose is preferably administered in two, three, four or more sub-doses per day. These sub-doses may be administered containing 10 to 1000 mg, preferably 20 to 500, per dosage unit.

although it is possible to administer the active ingredient alone, it is preferable to administer it in the form of pharmaceutical compositions. The compositions for both veterinary and human use of the invention comprise at least one active ingredient, together with one or more suitable carriers of the active ingredient and, 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, nasal, topical (including subcutaneous, intratricular, 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 comprising 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 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 surfactant or dispersant. 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 be coated or scored and formulated so as to provide slow or sustained release of the active ingredient.

preferably be regulated

In the case of infection of eyes or other external tissues, such as the mouth or skin, the compositions are preferably administered as topical ointments or creams containing the active ingredient in an amount of, for example, 0.075 to 20% by weight, preferably 0.2 to 15% by weight and most preferably 0.5 to 15%. 10% by weight. When an ointment is used, the active compounds can be used either with a paraffin base or with a water-miscible massage 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 with two or more hydroxy groups, such as propylene glycol, 1,3-butadiol, mannitol, sorbitol, glycerol and polyethylene 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 and skin penetration agents are dimethylsulfoxide and analogs thereof.

The oil phase of the emulsions of the invention may be constituted by known ingredients and may be manufactured in a known manner, although 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 fat or oil or both. oil. Preferably, a hydrophilic emulsifier is used together with a lipophilic emulsifier which acts as a stabilizer.

and

It is also preferred that this phase contain both oil and fat. An emulsifier or emulsifiers with or without a stabilizer 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. Direct or branched mono- or dialkyl esters such as diisoadipate, isocetyl stearate, coconut fatty acid propylene glycol diester, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a branched ester mixture known as Crodamol may be used. 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 as well as white soft paraffin and / or liquid paraffin or other mineral oils may be used.

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 solvent for 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.

Compositions suitable for topical administration in the mouth include tastes containing the active ingredient in a palatable base, usually sucrose and acacia or tragacanth. Pastilles contain the active ingredient in an inert basis such as gelatin or glycerin or sucrose and acacia. Mouthwashes contain the active ingredient in a suitable liquid carrier.

The formulations for rental administration may be in the form of suppositories with a suitable base comprising, for example, coconut butter or salicylate.

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 formulations 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 enhance the isotonicity of the composition with 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 multiple dose containers, eg sealed ampoules and vials, and may be stored in a lyophilized state, and prepared immediately by use only by the addition of 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. Suitable 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. For example, a composition suitable 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 compositions and may be in the form of solid, liquid or gaseous materials which are otherwise inert or veterinary compatible and miscible with the active ingredient. The veterinary compositions may be administered orally, parenterally, or by any other appropriate means.

For oral administration, the compositions may take the form of tablets, granules, wetting solutions, wafers with a special cap, capsule or feed supplement. Granules may be prepared by known wet granulation, compression molding or chopping techniques. The animals may be administered in an inert liquid vehicle in the form of a wetting solution or suspension with an aqueous or oily base. Preferably, additional ingredients such as a dispersant are 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 densifying or thickening agent may be used together with a humectant or wetting agent if the liquid diluent is water. In preparing the emulsion paste, it is convenient to use one or more surfactants. 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 compounds of formula I and their physiologically tolerated salts by removing protective groups from a compound of formula II

N.

CH2O (CH2) 2Ra where (II)

denotes amino or protected amino and denotes hydroxy or protected hydroxy, with the proviso that at least one of R a and R g is a protected group to form a compound of formula I or a physiologically tolerable salt or ester thereof and one or more of the following 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 salt shall be converted;

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

In the above process, the protecting groups may be selected, for example, from the group consisting of acyl groups such as C 1-4 alkanoyl groups such as acetyl or pivaloyl, or aroyl groups such as benzoyl, arylmethyl groups such as benzyl, or trialkylsilyl C1-C4 groups in each alkyl, for example triemtylsilyl.

Arylmethyl protecting groups can be removed, for example, by hydrogenolysis, for example by hydrogenation in the presence of Raney nickel or a palladium catalyst, or with sodium in liquid ammonia. Acyl protecting groups can be removed, for example, by hydrolysis using, for example, an amine such as methylamine or triethylamine, preferably in an aqueous medium. Trialkylsilyl protecting groups can be removed, for example, by solvolysis, for example by alcoholic or aqueous ammonia, or by alcoholysis.

The starting compounds used in the above process can be prepared by a conventional method, 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 I

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

A mixture of 2.48 g (7.13 mol) 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 is added. Shake under an atmosphere of hydrogen at an initial pressure of 34 kPa at 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, after filtration through a pad of Celite, was evaporated in vacuo and the resulting white solid was 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 the N-methylbenzamide and then recrystallised from I00% ethanol to give 2-amino-9- (2-hydroxyethoxymethyl) -9H-purine as analytically pure white granules, m.p. I86 to ^I87, Low: 14 ° 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-toluenesulfonic 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 diemtylformamide and acetonitrile and decolourisation with activated carbon gave 25.6 g of 2-acetamido-9- (2-acetoxyethoxymethyl) -6-mercapto-9H-purine as a yellow ^p evný genus ^{p kt} te ^pl of T ^and the OTE. 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 5 ml. Then 20 ml of acetone and the resulting precipitate was filtered and dried to give 0.21 g (65%) ^b l ^{e p e la} t evn ^{alkyl pl} of TE counting revolutions ^of 18 ^{s 8-189} ° C. Produ t ^to this ^NY with an authentic sample by TLC and NMR analysis.

SUBJECT OF THE INVENTION

Claims (4)

A process for the preparation of an antiviral active compound of formula I ch ₂ and ₂ ch ₂ oh and its physiologically tolerable salts, characterized in that the protecting group is removed from the compound of the general formula II (II), wherein: R @ 1 denotes amino or protected amino and Ra is a hydroxy or protected hydroxy group, 12 12 with the proviso that at least one of Ra and R < 6 > is a protected group to form a compound of formula I or a physiologically tolerable salt or ester thereof and one or more subsequent conversions as desired : (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 salt shall be converted; III) when the resulting product is an ester of a compound of formula I, said ester is converted to a base compound of formula I or a physiologically tolerable salt thereof. 2. A process according to claim 1, wherein the removal of the acyl protecting group is carried out by hydrolysis. 3. The process of claim 1 wherein the removal of the arylmethyl protecting group is by hydrogenolysis. 4. A process according to claim 1 wherein the removal of the trialkylsilyl protecting group is by solvolysis or alcoholysis.