CH632758A5 - Process for preparing substituted purines - Google Patents

Abstract

Substituted purines of the formula I are prepared by eliminating trialkylsilylamino or trialkylsilyloxy groups from the 2 and 6 positions. The elimination is effected by alcoholysis or by neutral solvolysis. The symbols in the formula I have the meaning given in Patent Claim 1. The compounds of the formula I and their salts are active against different type of viruses in vitro and in vivo. <IMAGE>

Description

The invention relates to a process for the preparation of substituted purines and their salts. The 15 esters of the 9- (2-hydroxyethoxymethyl) derivatives of guanine and 2,6-diaminopurine and the pharmaceutically acceptable salts of these compounds are preferably prepared.

It has now been found that substituted purines of the formula I

(I),

CH .O.CH .CH2OC.R

(II),

0

0

wherein Ro1 is trialkylsilylamino or trialkylsilyloxy and R3 is trialkylsilylamino which is subjected to alcoholysis or neutral solvolysis and, if the process product is the free base, is converted into an acid addition salt or an alkali metal salt or, if the process product is a salt, this into the free base or transferred to another salt.

2. The method according to claim 1, characterized in that one produces a compound of formula I, wherein R1 is hydroxy.

3. The method according to claim 1 or 2, characterized in that one produces a compound of formula I, wherein R2 is hydrogen or an alkyl group with a straight or branched chain and 2 to 8 carbon atoms.

4. The method according to claim 1 or 2, characterized in that a compound of formula I, wherein R2 is an aryl group substituted by a halogen atom, an amino, nitrilo- or sulfonamido group or an acyl or alkyl group having 1 to 4 carbon atoms, manufactures.

5. The method according to any one of claims 1, 2 or 4, characterized in that a compound of the formula I in which R 2 is a substituted aryl group having fewer than 10 carbon atoms is prepared.

6. The method according to claim 1, characterized in that 9- (2-formyloxyethoxymethyl) guanine is prepared.

35 where

R1 is a hydroxy or amino group; and R2 is hydrogen, a straight-chain or branched alkyl group having 2 to 16 carbon atoms, a naphthyl group or a substituted aryl group having 6 to 18 carbon atoms, preferably having less than 10 carbon atoms,

mean, are effective against viruses, namely against different types of DNA and RNA viruses in vitro and against DNA viruses in vivo. In particular, these compounds are particularly effective against herpes, cowpox and rhinoviruses, including herpes simplex, herpes zoster and chickenpox viruses in mammals, which cause diseases such as keratitis herpetica in rabbits and encephalitis herpetica in mice.

The invention accordingly relates to a process for the preparation of compounds of the formula I in which R1 and R2 have the meanings given above, or a salt thereof, in particular a pharmaceutically acceptable salt.

The compounds of the formula I in which R 1 is hydroxy or their salts are preferred, as are compounds in which R 2 is hydrogen or a straight-chain or branched alkyl group having 2 to 8 carbon atoms, with 2 to 4 carbon atoms being particularly preferred. If R2 is a substituted aryl group having 6 to 18 carbon atoms, preferably less than 10, the preferred substituents on the aryl group are halogen atoms, amino, nitrilo or sulfonamido groups, and acyl or alkyl groups having 1 to 4 carbon-65 atoms.

The most preferred compounds are:

9- (2-formyloxyethoxymethyl) guanine;

9- (2-propionyloxyethoxymethyl) guanine;

9- [2- (2,2-dimethylpropionyloxy) ethoxymethyl] guanine; and

2-amino-9- (2-formyloxyethoxymethyl) adenine.

These compounds are distinguished by their extraordinarily strong activity against herpes viruses.

Salts which are particularly suitable for therapeutic purposes are those of pharmaceutically acceptable acids such as lactic acid, acetic acid, malic acid or p-toluenesulfonic acid and the salts of pharmaceutically acceptable mineral acids such as hydrochloric acid or sulfuric acid. If R1 is a hydroxyl group, the pharmaceutically acceptable alkali metal salts are also suitable, the sodium salt being particularly preferred. Other salts can also be prepared and then converted into salts suitable for the respective treatment purpose.

The process according to the invention for the preparation of substituted purines of the formula I is characterized in that a compound of the formula II

CH

0

wherein Ro1 is trialkylsilylamino or trialkylsilyloxy and R3 is trialkylsilylamino, which is subjected to alcoholysis or neutral solvolysis, and if appropriate subsequently subsequently converted a compound of the formula I into another compound of the formula I; or if the product of one of the reactions described above is the free base, optionally converting it into an acid addition salt or an alkali metal salt or, if the product obtained is a salt of a compound of the formula I, if appropriate converting it into another salt or the base thereof releases.

The starting compound of formula II, in which both the amino group in the 2-position and the substituent in the 6-position is protected by a trialkylsilyl group, can be prepared by condensing a trialkylsilylated purine with an ester or diester. According to a preferred embodiment, a purine, which has the desired substituents in the 2- and 6-position, is condensed with a 2-halomethoxy oxyethanol protected by an acyl group or an acyloxymethoxy ethanol protected by an acyl group, e.g. 2-propionyloxyethoxymethyl chloride or butyryloxyethoxymethyl acetate, in a strongly polar solvent such as dimethylformamide (DMF) and in the presence of a base, e.g. Sodium hydride. The reaction is preferably carried out at room temperature over a longer period of time. It may take several hours or even days to get reasonable yields.

The protective groups mentioned are very unstable and are solved by solvolysis e.g. removed with alcoholic or aqueous ammonia or by alcoholysis.

The process according to the invention is based on intermediates obtained from monosubstituted purines

632758

can be. Such purines are readily available and can be prepared by processes known per se, which are described in the literature and in text books such as “Heterocyclic Compounds-Used Pyrimidines Part II Purines”, published by DJ Brown (1971), published by Wiley-Interscience will.

A compound of formula I obtained according to the invention can optionally be converted into another compound of formula I by transesterification. Such a conversion can be carried out, for example, by reacting the compound of the formula I with a suitable carboxylic acid; for example, propionic acid is required for the production of 9- (2-propionyloxyethoxymethyl) guanine. In certain cases, the acid can act as an acid catalyst at the same time, but in other cases an additional acid catalyst is required, for which p-toluenesulfonic acid is suitable.

The compounds of formula I obtainable according to the invention and their pharmaceutically acceptable salts can be processed together with pharmaceutically acceptable carriers to give pharmaceutical preparations and preparations. In a particular exemplary embodiment of a pharmaceutical preparation, a compound of the formula I is in the form of an “effective single dose” preparation.

The term "effective single dose" used above means a predetermined amount effective against viruses which is sufficient to control the virus organism in vivo. Pharmaceutically acceptable carriers are substances that are suitable for the administration of the drug. They can be solid, liquid or gaseous, and they should also be inert, medically acceptable and compatible with the active ingredients.

These pharmaceutical preparations can be administered parenterally, orally, as suppositories or as a pessary; furthermore, they can be administered locally as ointment, cream, aerosol, powder or in the form of eye or nose drops. The particular form of preparation depends on whether an internal or external virus infection is to be treated.

In the case of internal infections, the preparations are usually administered orally or parenterally in doses of 0.1 to 250, preferably 1 to 50, mg / kg body weight of the mammal, the amount of the active ingredient being calculated in relation to the free base. In humans, these compounds are administered in the form of single doses, several times a day, in an amount of 1 to 250 mg per single dose.

For oral administration, fine powders or granules are suitable which contain diluents, dispersants and / or surface-active agents and in a mixture, either in water or in a syrup, in capsules or sachets in the dry state or in a non-aqueous solution or Suspension, which may contain suspending agents, can be offered. The preparations for oral administration can also be in the form of tablets, in which binders or lubricants can be incorporated, or in the form of a suspension in water or syrup. In addition, if desired or necessary, flavorings, preservatives, suspending agents, thickeners or emulsifiers can be added. Of the preparation forms mentioned, tablets and granules are preferred, which can also be provided with a coating.

For parenteral administration or for administration in the form of drops, for example in the case of eye infections, the compounds can be dissolved in an aqueous solution in a con

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concentration of 0.1 to 10%, preferably 0.1 to 1% and in particular 0.2% (w / v). These solutions can contain antioxidants, buffers and / or other additives.

In case of infections of the eye or other external tissues, e.g. In the mouth or on the skin, the preparations are preferably applied directly to the infected part of the body as a topical ointment or cream. The compounds can be in an ointment, for example with a water-soluble ointment base, or in a cream, for example with an 01-in-water cream base, in a concentration of 0.1 to 10%, preferably 0.3 to 3% and in particular 1 % (W / v).

The following examples serve to illustrate the invention.

example 1

Preparation of 9- (2-propionyloxyethoxymethyl) guanine

A mixture of 4.9 g (0.03 M) guanine, 3.6 g ammonium sulfate and 225 ml hexamethyldisilazane was heated under reflux under nitrogen for 20 hours. Excess hexamethyldisilazane was removed by distillation under reduced pressure. 40 ml of dry toluene was added to the remaining oil, followed by 11.6 ml (0.083 M) of dry triethylamine and 6.6 g (0.04 M) of 2-propionyloxy-ethoxymethyl chloride in 40 ml of toluene. The mixture was refluxed under nitrogen for 6 hours, 5 ml of triethylamine was added and refluxing was continued for an additional 18 hours.

After the reaction solution was cooled to room temperature, 100 ml of ethanol was added and the mixture was heated under reflux with stirring for 15 minutes. The solvents were removed by flash evaporation under vacuum. The semi-solid residue obtained was taken up in 300 ml of acetone, followed by 150 ml of ethanol. The washing liquids acetone and ethanol were combined, evaporated to dryness under vacuum and taken up in water. Recrystallization from water gave 3.1 g of 9- (2-propionyloxyethoxymethyl) guanine, the NMR and UV spectra of which were identical to those of a known sample of this compound. The yield was 37% and the melting point was 223 to 226 ° C.

Example 2

Preparation of 9- [2- (3-chlorobenzoyloxy) ethoxy-methyljguanine

78.3 g (0.5 M) 3-chlorobenzoic acid (1 M), ethylene glycol and 15 g of a cation exchange resin (50 to 100 mesh) in the hydrogen form are mixed together and heated under reflux with stirring in 180 ml of toluene for 18 hours. A Dean-Stark trap is attached to the reaction vessel to catch the water formed.

The toluene is removed by evaporation under a water jet vacuum and the remaining liquid is distilled at a pressure of 0.25 mm.

The fractions were examined using NMR. The yield of 2- (3-chlorobenzoyloxy) ethanol was 67%.

Drier hydrogen chloride is introduced into a cooled (0 ° C) suspension of 12.4 g (0.06 M) 2- (3-chlorobenzoyl-oxy) ethanol and 1.8 g (0.02 M) paraformaldehyde in 500 ml dichloromethane until the solids have dissolved and the mixture is saturated with hydrogen chloride. The mixture was dried over molecular sieves and calcium chloride, filtered and the solvents were removed by flash evaporation at 30 ° C.

The remaining oil was examined by NMR and used directly. The yield was about 75% of theory.

A mixture of 1.0 g (6.6 mM) guanine, 0.73 g ammonium sulfate and 40 ml hexamethyldisilazane was refluxed under nitrogen overnight. Excess hexamethyldisilazane was distilled off under reduced pressure. 30 ml of dry toluene was added to the remaining oil, followed by 0.12 g (0.7 mM) p-toluenesulfonic acid and 1.6 g (6.9 mM) 2- (3-chlorobenzoyloxy) ethoxy-methyl chloride. The mixture was then refluxed under nitrogen overnight.

The solvent was removed by flash evaporation and the remaining oil heated on a steam bath in methanol for 10 minutes. The mixture was cooled, filtered and the precipitate which precipitated was recrystallized twice from methanol. 1.5 g of analytically pure (analyzed as hemihydrate) 9- [2- (3-chlorobenzoyloxy) ethoxymethyl] guanine were obtained, which corresponds to a 60% yield. The melting point was 218 to 220 ° C.

Example 3

Preparation of 9- (2-p-toluoyloxyethoxymethyl) guanine

68.08 g (0.5 M) p-toluic acid, 62.07 g (1 M) ethylene glycol and 15 g (50 to 100 mesh) cation exchange resin in the hydrogen form were mixed and refluxed in 180 ml toluene for 18 hours with stirring. A Dean-Stark trap was attached to the reaction vessel to catch the water formed.

The toluene was removed by evaporation under a water jet vacuum and the remaining liquid was distilled to 0.25 mm pressure.

The fractions were examined by NMR spectroscopy. The yield of 2- (p-toluoyloxy) ethanol was 67%.

Drier hydrogen chloride is introduced into a suspension of 10.8 g (0.06 M) 2- (p-toluoyloxy) ethanol and 1.8 g (0.02 M) paraformaldehyde in 500 ml dichloromethane, cooled to 0 ° C., until the Solids were dissolved and the mixture was saturated with hydrogen chloride. The mixture was dried over molecular sieves and calcium chloride, filtered and the solvents removed by flash evaporation at 30 ° C.

The oil obtained was examined by NMR spectroscopy and used directly. The yield was approximately 75%.

A mixture of 1.0 g (6.6 mM) guanine, 0.73 g ammonium sulfate and 40 ml hexamethyldisilazane was refluxed under nitrogen overnight. Excess hexamethyldisilazane was distilled off under reduced pressure. 30 ml of dry toluene was added to the remaining oil, followed by 0.12 g (0.07 mM) of p-toluenesulfonic acid and 1.58 g (6.9 mM) of 2- (p-toluoyloxy) ethoxy-methyl chloride. The mixture was refluxed under nitrogen overnight.

The solvent was removed by flash evaporation and the remaining oil was heated in methanol on a steam bath for 10 minutes. The mixture was cooled, filtered and the precipitate recrystallized twice from methanol. 1.19 g of analytically pure (analyzed as hemihydrate) 9- (2-p-toluoyloxyethoxy-methyl) guanine with a melting point of 220 to 221 ° C. were obtained. This corresponds to a 55% yield.

Example 4

Preparation of 9- (2-a-naphthoyloxyethoxymethyl) guanine

86.09 g (0.5 M) 9-naphthoic acid, 62.07 g (1 M) ethylene glycol and 15 g cation exchange resin in the hydrogen form were mixed and heated under reflux in 180 ml toluene for 18 hours. A Dean

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Stark trap was attached to the reaction vessel to catch the water formed.

The toluene was evaporated under a water jet vacuum and the remaining liquid was distilled at a pressure of 0.25 mm.

The fractions were examined by NMR spectroscopy. The yield of ethylene glycol mono-a-naphthoate was 67%.

Dry hydrogen chloride was introduced into a suspension of 12.97 g (0.06 M) ethylene glycol mono-a-naphthoate and 1.8 g (0.02 M) paraformaldehyde in 500 ml dichloromethane, cooled to 0 ° C., until the solids dissolved and the mixture was saturated with hydrogen chloride. The mixture was dried over molecular sieves and calcium chloride, filtered and the solvents were removed by flash evaporation at 30 ° C.

The remaining oil was examined by NMR spectroscopy and used directly. The yield was approximately 75%.

A mixture of 1.0 g (6.6 mM) guanine, 0.73 g ammonium sulfate and 40 ml hexamethyldisilazane was refluxed under nitrogen overnight. Excess hexamethyldisilazane was removed by distillation under reduced pressure. 30 ml of dry toluene was added to the remaining oil, followed by 0.12 g (0.7 mM) p-toluenesulfonic acid and 1.83 g (6.9 mM) 2- (a-naphthoyl-oxy) ethoxymethyl chloride. The mixture was refluxed under nitrogen overnight.

The solvent was removed by flash evaporation and the remaining oil was heated in methanol on a steam bath for 10 minutes. The mixture was cooled, filtered and the precipitate recrystallized twice from methanol. 1.18 g of analytically pure 9- (2-a-naphthoyloxyethoxymethyl) guanine with a melting point of 219 to 220 ° C, i.e. 47% yield.

Example 5

Preparation of 9- (2-formyloxyethoxymethyl) guanine

Hydrogen chloride was introduced into a suspension of 3.6 g of ethylene glycol monoformate and 1.18 g of paraformaldehyde in 100 ml of dry dichloromethane, cooled to 0 ° C., until the mixture was saturated. The oily suspension was dried over molecular sieves and anhydrous calcium chloride, filtered and the solvent was removed by flash evaporation (bath temperature below 30 ° C.). 2-Formyloxyäthoxymethylchlorid was obtained.

A solution of 13 mM tris-trimethylsilylguanine and 2.5 g of the 2-formyloxyethoxymethyl chloride obtained above was dissolved in 50 ml of dry toluene and heated under reflux under nitrogen for 24 hours. After removal of the solvent by flash evaporation

5 632758

the remaining oil was stirred in methanol at room temperature for 1 hour. The methanol was evaporated and the residue was recrystallized from dimethylformamide and acetonitrile. The 9- (2-formyloxyethoxy-s methyl) guanine obtained had a melting point of 225 to 227 ° C.

Example 6

Preparation of 9- (2-propionyloxyethoxymethyl) guanine hydrochloride io The pH of a solution of 300 mg of 9- (2-propionyloxyethoxymethyl) guanine in 400 ml of ethanol was measured with ethereal hydrochloric acid at room temperature to 1.0, using a Broadband pH paper, discontinued. The solution was diluted to a volume of 1.91 with dry ether and cooled overnight. The precipitated granules were filtered, washed with ether and dried in a desiccator under reduced pressure for 3 days. They were further dried at 3.5 mm Hg for 2.5 hours. 260 mg of 9- (2-propionyloxyethoxy-20 methyl) guanine hydrochloride with a melting point of 125 to 131 ° C. were obtained. The elemental analysis and the NMR spectrum (DMSO-ds) corresponded to the above compound. The silver nitrate test was positive for halogen.

2s Example 7

Sodium salt of 9- (2-propionyloxyethoxymethyl) guanine 125 mg of 9- (2-propionyloxyethoxymethyl) guanine was added to 44.5 ml of a cooled 0.01N sodium hydroxide solution with stirring. The mixture was frozen and lyophilized. The sodium salt of 9- (2-propionyloxyethoxymethyl) guanine was obtained. Elemental analysis, NMR and IR spectra corresponded to the above compound.

Preparations

3s 1) A tablet preparation containing a mixture of 100 mg 9- (2-formyloxyethoxymethyl) guanine, 200 mg lactose, 50 mg starch, 5 mg polyvinylpyrrolidone and 4 mg magnesium stearate was prepared by wet granulation.

2) A tablet preparation containing a mixture of 100 mg 4o2-amino-9- (formyloxyethoxymethyl) adenine, 200 mg lactose, 50 mg starch, 5 mg polyvinylpyrrolidone and 4 mg magnesium stearate was prepared by wet granulation.

3) A tablet preparation containing a mixture of 100 mg 4s 9- (2-propionyloxyethoxymethyl) guanine, 200 mg lactose,

50 mg of starch, 5 mg of polyvinylpyrrolidone and 4 mg of magnesium stearate was prepared by wet granulation.

4) A tablet preparation containing a mixture of 100 mg of 5o9- [2- (2,2-dimethylpropionyloxy) ethoxymethyl] guanine,

Containing 200 mg lactose, 50 mg starch, 5 mg polyvinylpyrrolidone and 4 mg magnesium stearate was prepared by wet granulation.

B

Claims (4)

632 758 2nd PATENT CLAIMS 1. Process for the preparation of substituted purines of the formula I CD, CH2.O.CH2 , CH_OC.R 2 II 0 wherein R1 is a hydroxy or amino group; and R2 is hydrogen, an alkyl group with a straight or branched chain and 2 to 16 carbon atoms, a naphthyl group or a substituted aryl group with 6 to 18 carbon atoms, characterized in that a compound of the formula II R 1 "o N N ' CH2.O.CH2.CH2OC.R 7. The method according to claim 1, characterized in that 9- (2-propionyloxyethoxymethyl) guanine is prepared. 8. The method according to claim 1, characterized in that 9- [2- (2,2-dimethyl-propionyloxy) ethoxymethyl] - 5 guanine. 9. The method according to claim 1, characterized in that 2-amino-9- (2-formyloxyethoxymethyl) adenine is prepared. 10th