DK147824B - ANALOGY PROCEDURE FOR PREPARING 9- (2-ACYLOXYETHOXYMETHYL) -PURINES OR SALTS THEREOF - Google Patents

Description

U782A

The present invention relates to an analogous process for the preparation of 9- (2-acyloxyethoxymethyl) purines of formula I: R1

• GH2.0.CH2.CH20. ^ .R

Wherein R represents a hydroxy or ammo group and R represents a straight or branched chain alkyl group of 2-6 carbon atoms, or salts thereof.

2 147024

It has been found that substituted purines of formula (I) have antiviral activity against various genera of DNA and RNA viruses in vitro and against DNA viruses in vivo. In particular, the compounds are particularly active against herpes, vaccinia, and rhino viruses, with herpes viruses including simplex, zoster, and varicella in mammals causing such diseases as, for example, herpetic keratitis in rabbits and herpetic encephalitis mouse.

Those compounds of formula (I) wherein hydroxy, or a salt thereof, 2 are preferred, as are compounds wherein R is a straight or branched alkyl group of 2-4 carbon atoms.

The most preferred compounds are 9- (2-propionoyloxyethoxymethyl) -guanine and 9- [2- (2,2-dimethylpropionoyloxy) -ethoxymethyl] -guanine, in particular because of their very high antiviral effect against herpes.

The salts may be of pharmaceutically acceptable organic acids such as lactic acid, acetic acid, malic acid or p-toluenesulfonic acid, or of pharmaceutically acceptable mineral acids such as hydrochloric acid or sulfuric acid. When R 1 is hydroxy, pharmaceutically acceptable alkali metal salts, preferably the sodium salt, may be used.

Other salts can also be prepared and then converted into salts that are directly suitable for treatment purposes.

The process is peculiar to the characterizing part of claim 1.

It is known that related 9- (2-acyloxyethoxymethyl) purines have antiviral effect, as described in Danish Patent Application No. 3926/75. According to said patent application, inter alia, compounds similar to the above formula I are prepared, but wherein the substituent at the 9-position has a different meaning and e.g. may represent 2-hydroxyethoxymethyl, 2-carboxypropionyloxyethoxymethyl or 2-acetoxyethoxymethyl. However, these known compounds are less absorbed than desired by oral administration.

Compounds prepared according to the present invention are substantially better absorbed than said known compounds, as demonstrated by experiments with rats.

In these experiments, an aqueous suspension of the compound to be tested was administered orally to rats corresponding to 25 mg / kg of 9- (2-hydroxyethoxymethyl) guanine. The urine of the rats was collected over a 24 hour period and the amount of the compound concerned in the urine was determined by high pressure liquid chromatography. The amount of the compound determined in the urine, calculated as a percentage of the administered dose, was taken as a measure of the amount absorbed in 24 hours. The results are shown in the following table: 147824 3 u i

W C

cn ρ <U> 60 P. β 05 Ή 60 +++ + Ρ P +++ ++ +

Ai · Η μ g V i

-ΰ .h I P Ai µ P

• H i — I

.5 ft 4J Td $% CO iw

• ι-l ClJ

CO

O 00 JJ X) Ai Q) · ~~ n β 60 / -1-

©. CM co P Yes CM

1-1 ih ih Td m ή • η Λ ρ p 1— td

0 tH

η Η Η Ή (0 H

• Η · Η · Η M W td · Η

μ β β ρ γη P

P in co S 0) (U in μ g g -S xj x) g

• Η P ρ Ρ η p Ρ P

g p p <u · η p

w · η ρ p ο μ Ai C

• hh ρ p 1- ρ μ <u tn 60 60> O 60 o <r Ή w .H CO IH 'T3 cm _ _ tn o m o o ihih xj m w σι m oo

ClJ Cd 1 «« «« «σι cn cm T- i- xt

t-s cn CM CM

λ L

µ t M -S g P

p jS P p, Ρ · Η Η Η Η Ρ Ρ ρ ρ ρ ρ PS PS Ρ 05 60 / -> Ρ • Η · Η γΗ '—- ^ ι 60 Ρ 05 ΡΧΡ lOPrH ^^ - x Μ Ρ POP PTdÉnOt-l, Η ιΗ d Ρ 3 ι-Ι β Ad tH>.

Ρ ι — I 60 Η 60 rH · Η Η!, Ρ • Ρ · λ λ Ρ λ · ΗΙΗ Ρ Ρ Η

Ρ Η rH ^ irM HP-SOP

• Η ιη >>! 1! >> tnO >> 1Hg X 0 rd Ο Ad 6 1 & μ pin η ιΗ η ρρ o o I1! ο μη- pf-, ρ μ 60 Ad t-ι ο

ΙΗ ΙΗ · ^ - g Ρ 0 Μ-ΙιΗ HP.AJ

ιΟ FiO η »'θ-ΡτΗΗ Η θ cm« · µ tf MIW >> ^ ^ ρ ο σι ορ <ο ο · µ X Ad

μ cn cn Ad ο Ad id oh X

ρ η μ η prHppo μ λ · ρ pu Ρ 1 Ρ ί> ι 0 Η Η η μμ>!> -, μ · Ρ ρ · ηρ> χ μ Ρβ X ί4 Κ Ρ «5 ° 722 • Η 05 ΟΟ Ο 050 -ΗΙΡβ ρ Η 60 μ Ad Η γ-Ι 05 ft CM 60 Ρ • Η Pp Ρ) μ Ρ Ρ 60 Ο 1> I tt g χ3 · η? 1, ρ ο -d β μ cm ι — ι ρ Ό ΡΡ Ad Ο β Ρ ΡΡ Ρ. 3

<3 · Η 60 1 I · Η I · Η 60 I I Ρί I

Α5 & CMCMpCM Ad 0 CM CM Ad CM

J_j tø n— 'fij v— ^ d) v— ^ i — t JJ' w 'on iipi ομ i <Si ·

PuP σισΐ6οσι ft ih σι σι g σι · · · · · cm cn -σ m io 4 14782 / »

These test results show that compounds 4, 5 and 6 are superior to compounds 1, 2 and 3 in terms of their ability to be absorbed from the intestinal tract after oral administration.

In process a), the leaving atom or leaving group Å is preferably a reactive residue of an organic or inorganic acid and can therefore be a halogen atom or a sulfonate group and Q is hydrogen or an alkali metal, preferably sodium. The preferred process comprises condensing a purine having the desired 2- and 6-substitution with an acyl-blocked 2-halo-genomethoxyethanol or an acyl-blocked acyloxymethoxyethanol, for example, 2-propionoyloxyethoxymethyl chloride or butyryloxyethoxymethyl acetate, in a strong 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 prolonged period of time, i.e. that several hours or even days may be necessary to obtain reasonable yields.

In process h), an alcohol of formula (V) is reacted with a suitable acylating agent such as a carboxylic acid, an aliphatic or aromatic anhydride, an aliphatic or aromatic acyl halide, a mixed carbonic-carboxylic anhydride or a carboxylic acid ester. Compounds of formula (V) can be prepared by the processes described in German Publication No. 2,539,963.

In process c), one or both of the amino group at the 2-position and the substituent at the 6-position can be reversibly blocked with a blocking group, for example a trialkylsilyl group, an activated acyl group or a benzyloxycarbonyl group, but these last two types of groups will only block r \ when this is amino. When both the amino group at the 2-position and the substituent at the 6-position are blocked with a trialkylsilyl group, such a compound will be the product of the condensation of a trialkylsilylated purine and an ester or diester similar to process a). Such blocking groups are very labile and can be removed by solvolysis with alcoholic or aqueous ammonia or by alcoholysis.

One or both of the 2- and 6-positions of the purine ring may be blocked by an activated acyl group such as a trihalogenoacyl group, e.g. trichloroacetyl, which together with the amino group it blocks, forms a trichloroacetamido group. The 6-position of the purine ring is blocked only when it is substituted by an amino group. Such groups can be reductively cleaved. If the blocking group is a benzyloxycarbonyl group, it can also be removed by reductive cleavage.

Methods a) to c) are all based on intermediates which can be prepared from simply substituted purines. Such purines are, of course, readily available by techniques known per se found in literature 5 U7824 and in textbooks such as "Heterocyclic compounds - Fused Pyrimidines Part II Purines ed. By D. J. Brown (1971) published by Wiley-Interscience".

A compound of formula (I) prepared by one of processes a) to c) may, if desired, be converted to another compound of formula (I) by transesterification. Such conversion can be achieved by reacting a compound of formula (I) with a suitable carboxylic acid. For example, to prepare 9- (2-propionoyloxyethoxymethyl) -guanine reaction with propionic acid is required. In some cases, the acid may also act as an acidic catalyst, but in other cases an additional acidic catalyst, e.g. p-toluenesulfonic acid.

The compounds or their salts can be administered orally or parenterally at dosage levels, calculated as the free base, of approx. 0.1 to 250 mg per preferably 1 to 50 mg / kg of mammalian body weight, and they are used in humans in a unit dosage form given a few times daily in an amount of 1 to 250 mg per day. unit dose.

For oral administration, fine powders or granules may contain diluents or dispersants and / or surfactants and may be administered in a beverage, in water or in a syrup, in dry state capsules or bags, or in a non-aqueous solution or suspension containing suspending agents are present in tablets which may contain binders and lubricants, or in a suspension in water or in a syrup. Tablets and granules are preferred and these may be coated.

For parenteral use or for use as drops, such as in eye infections, the compounds may be present in aqueous solution at a concentration of from ca. 0.1 to 10%, preferably 0.1 to 17, and most preferably 0.27. w / v. The solution may contain antioxidants, buffers, etc.

Alternatively, in the case of infections of the eye or other external tissues, e.g. mouth and skin, preferably the infected portion of the patient's body is applied as a local ointment or cream. The compounds may be present in an ointment, for example, with a water-soluble ointment base, or in a cream, for example, with an oil-in-water cream base, at a concentration of from ca. 0.1 to 10%, preferably 0.3 to 3% and more preferably 1% w / v.

Example 1, (Method b)

Preparation of 9- (2-hexanoyloxyethoxymethyl) guanine.

9- (2-Hydroxyethoxymethyl) -guanine (1.0 g), prepared by the processes described in German Publication No. 2,539 ° 3, was dissolved in dry dimethylformamide (70 ml) by heating on a steam bath, and the solution was cooled to room temperature and dry pyridine (10 ml) and hexanoic anhydride (9.4 g) were added. After stirring at room temperature for 4 days, TLC (silica gel in 10% methanol / chloroform) showed that the reaction was complete.

6 147824

The yellow reaction solution was diluted with ethyl acetate to a volume of 800 ml and cooled for several days. The fine white powder which precipitated was filtered off, dried and recrystallized from dry acetonitrile to give 400 mg (28%) of white granules, m.p. 221-223 ° C.

Example 2 ((Method a))

Preparation of 9- (2-propionoyloxyethoxymethyl) guanine.

(A) Ethylene glycol (31 g), propionic acid (18.5 g) and 7.5 g strong hydrogen ion resin, Bio Rod AG 50 WX-4 in 100 ml of toluene was refluxed with stirring under a Dean Stark scavenger for 18 hours. .

Toluene was removed by flash evaporation and the remaining liquid was distilled. The initial course of ethylene glycol was followed by distillation of the desired product, ethylene glycol monopropionate. NMR sample was used to determine purity. Yield 70%.

(B) Dry gaseous hydrogen chloride was introduced into the cooled (0 ° C) suspension of ethylene glycol monopropionate (7.1 g) prepared above and parafomaldehyde (1.8 g) in dichloromethane (50 ml) until the solid was dissolved and the mixture was saturated with hydrogen chloride. After drying over molecular sieves and calcium chloride, the mixture was filtered and the solvent was removed by flash evaporation at 30 ° C.

The residual oil of 2-propionoyloxyethoxymethyl chloride was used directly. Yield 60%.

(C) Sodium hydride (2.53 g) in the form of a 57% mineral oil dispersion was washed with dry bexane and added to a solution of guanine (4.53 g) in 100 ml of dry dimethyl sulfoxide and the mixture was stirred at 30 °. C for 23 hours.

2-Propionoyloxyethoxymethyl chloride (5.5 g) was added and the reaction mixture was stirred at 20 ° C for 18 hours. The solution was filtered and the solvent removed by flash evaporation in vacuo. The evaporation residue was cooled in an ice bath, dissolved in water and neutralized with acetic acid.

After standing for one hour, the product was filtered off, washed with water and dried. Recrystallization (3 times) of boiling acetonitrile gave 9- (2-propionoyl-oxyethoxymethyl) guanine. Yield 35%, m.p. 223-226 ° C.

Example 3, (Method b)) 9- (2-Propionyloxyethoxymethyl) guanine.

A mixture of 9- (2-hydroxyethoxymethyl) -guanine (1.0 g) and dry dimethylformamide (50 ml) was heated on a steam bath until most of the solid dissolved. It was then cooled to room temperature. Dry pyridine (10 ml) and propionic anhydride (2.9 ml) were added and the mixture was stirred at room temperature overnight. Additional propionic anhydride (1.0 ml) was added and the mixture was stirred for an additional 18 hours. The reaction mixture was diluted with ethyl acetate and cooled and the resulting solid was removed by filtration. This was recrystallized from dimethylformamide to give 9- (2-propionyloxyethoxymethyl) guanine (0.9 g), m.p. 223-226 ° C.

Example 4 (Process b)) 9- [2- (2,2-Dimethylpropionyloxy) ethoxymethyl] guanine.

A landing of 9- (2-hydroxyethoxymethyl) guanine (2.46 g), dry pyridine (400 ml) and pivalic anhydride (6.5 ml) was heated on a steam bath for a total of 33 days.

On the 11th day, additional pyridine (150 ml) was added and on the 27th day dimethylformamide (50 ml) was added. Volatiles were removed under reduced pressure and the residue evaporated with ethyl acetate. The insoluble solid was removed by filtration and dissolved in methanol-acetone. Silica gel (3 g) was added and the solvent was evaporated. The residue was added to a column of silica gel (180 g) in acetone. Elution with acetone gave an initial fraction of Ν, Ο-diacylated material, followed by a fraction containing the desired monoacylated product. The acetone was evaporated from this latter fraction and the residue was recrystallized from dimethylformamide acetonitrile ether acetate to give 9- [2- (2,2-dimethylpropionyloxy) ethoxymethyl] guanine (0.5 g), m.p. 245-246 ° C.

Example 5 (Method b))

Preparation of 9- (2-butyryloxyethoxymethyl) guanine.

A solution of sodium methoxide in dry methanol (10 ml) was added to a methanolic solution of 9- (2-hydroxyethoxymethyl) guanine at room temperature. Removal of the solvent in vacuo gave the sodium salt of the purine as a white powder.

The above sodium salt was suspended in a mixture of ethyl butyrate and dry DMF (20 ml) and refluxed with stirring. After 3 1/2 days, most of the solid was dissolved, then the reaction mixture was concentrated to dryness in vacuo and the residue was dissolved in 2N acetic acid (15 ml). Removal of the solvent in vacuo gave a semi-solid mass which solidified after treatment with water (15 ml) and SD3A (15 ml) with removal of the solvents in vacuo. This product was slurried with SD3A (25 ”1), filtered and air dried to give 195.2 mg of a tan solid.

Claims (6)

Example 6 (process c)) 9- (2-propionyloxyethoxymethyl) guanine. A mixture of 4.9 g, 0.03M guanine, 3.6 g ammonium sulfate and 225 ml of hexa-methyldisilazane 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 residual oil, followed by 11.6 ml, 0.083M, triethylamine and 6.6 g, 0.04M, 2-propionyloxyethoxymethyl chloride in 40 ml of toluene. The mixture was refluxed under nitrogen for 6 hours, 5 ml of triethylamine was added and the reflux continued for 18 hours. After cooling the reaction solution to room temperature, 100 ml of ethanol was added and the mixture was refluxed with stirring for 15 minutes. Solvent was removed by instantaneous evaporation in vacuo. The resulting semi-solid residue was triturated with 300 ml of acetone followed by 150 ml of ethanol. Acetone and ethano1 rinses were combined, evaporated in vacuo to dryness and triturated with water. Recrystallization from water gave 3.1 g of 9- (2-propionyloxyethoxymethyl) guanine, whose NMR and UV spectra were identical to corresponding spectra from authentic material. The yield was 37%, m.p. 223-226 ° C. 1. Analogous Process for the Preparation of 9- (2-Acyloxyethoxymethylphthyl) -purines of Formula (I): R1] V \ CH2.0.CR2.CH20.jj.R2 1. 2 wherein R represents a hydroxy or amino group and R represents a straight or branched alkyl group of 2-6 carbon atoms, or salts thereof, characterized in that a) a compound of formula (XI): R 1) Q 147824. wherein R is as defined above and Q is hydrogen or an alkali metal, is reacted with a compound of formula (III) A-CH-O-CEL-CIVOC-R2 (III) 2 2 2, 0 2 wherein A represents a or R) has the meaning given above, or b) an alcohol of the formula (V) Jxy h9it in 2 ch2.o.ch2.ch2.oh is esterified by reaction with an acylating agent, or c) blocking groups is removed from a compound of formula (I) wherein one or both of the 2-amino group and the R 2 substituent are blocked and that, if desired, the compound of formula (I) is obtained by any of the methods a ) to c) is converted to another compound of formula (I) by transesterification, or that, when the product of a h any of the above reactions is a base, if desired, the product is converted to an acid addition salt or to an alkali metal salt thereof, or when the product is a salt of a compound of formula (I), this salt if desired is converted to the corresponding base or to another salt thereof. Process according to claim 1, characterized in that A represents halogen or sulfonate. Process according to claim 2, characterized in that when A is halogen and Q is hydrogen, the reaction is carried out in the presence of a base. 4. A process according to claim 1, characterized in that the acylating agent is a carboxylic acid, an aliphatic or aromatic anhydride, an aliphatic or aromatic acyl halide, a mixed carbonic carboxylic anhydride or a carboxylic acid ester. 5. A process according to claim 1c, k characterized in that the R * and the amino group are blocked with a trialkylsilyl group and that this blocking group is removed by solvolysis or alcoholysis. Process according to claim 1, characterized in that when in form ~ 1. in 2 (I) R represents amino, both the R and R amino group are blocked with an activated acyl group or a benzyloxycarbonyl group, which blocking groups are removed by reductive cleavage.