PH26922A - Purinyl cyclobutanes - Google Patents

Description

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PURINYL CYCLORUTANES

BRIEF DESCRIPTION OF THE INVENTION

Antiviral activity is exhihited by compounds having the formula 5 . I i Ho

R,0-CH C R 2-12 1

NSN

C C

ZN /\

H C H, /%

H OR, and pharmaceutically acceptable salts thereof. In formula I, and throughout the specification, the symbols are as defined helow,

Ry is

Oo X

I !

N N = (Lr CC 3 NT x } N NT OX; wherein X15 Xo and X35 is independently hydrogen or amina, with the proviso that if Xo ig hydrogen, Xa is amino;

Ro is hydrogen, =PO,H, or 0 . 1 “C-Xg wherein Xy is alkyl, substituted alkyl, aryl; and ’ Ry is hydrogen or

OQ

I

-C-X4» with the proviso that when Ro is -PO4H,, Ry is hydrogen 3 : - al oriGIV oy and when Ry is

Q

[ ~C-Xy -, Roy is : 0 i

I

-C-Xy

Listed below are definitions of terms used to describe the compounds of this invention. These definitions apply to the terms as they are used throughout the specification (unless they are atherwise limited in specific instances) either individually or as part of a larger group.

The term "acyl" refers to phenyl and phenyl suhstituted with one, two or three substituents.

Preferred substituents are alkyl of 1 to 6 carhans, alkoxy of 1 to 6 carbons, halogen, trifluoromethyl, amine, alkylamine, dialkylamino, nitre, cocyano, alkanoyloxy of 2 to 11 carbons, carhoxy, carbamoyl and hydroxy.

The term "alkyl" refers to hath straight and hranched chain groups. Those groups having 1 to 10 carbon atoms are preferred.

The term "substituted alkyl” refers to alkyl groups having one, or more, substituents. Preferred suhstituents are halogen, amine, azide, hydroxy, cvano, trialkvlammonium wherein each alkyl group has 1 to B carbons, alkoxy of 1 to A carhons, aryl and carhoxy.

DETAILED DESCRIPTION OF THE INVENTION

The cvelohutanes nf formula 1, and the pharmaceutically acceptahle salts thereof, are antiviral agents that can he nsed to treat viral infections in © oRaNA 2 phD _— _

mammalian species such as domesticated animals (e.g. dogs, cats, horses and the like) and humans, and avian species (e.g., chickens and turkevs). They are effective against herpes simplex virus 1 and 2, varicella-zoster virus, acytomegalovirus, and vaccinia virus. They may also he effective against a variety of

DNA and RNA viruses. Exemplary DNA viruses in addition to those named above include herpes viruses (e.g.,

Epstein-Barr virus, pseudorahies virus, and the like}, other poxviruses (e.g., monkey pox and myxoma), papovaviruses (e.g., the papilloma viruses), hepatitis B virus, and adenoviruses. Exemplary RNA viruses are the retroviruses (e.g., human immunodeficiency viruses), rotaviruses, influenza viruses, paramyxoviruses, sand picnrnoviruses such as the rhinoviruses. The compounds of this invention may he administered parenterally (for example, by intravenaus, Sntraperitonenl or intramuscular injection), arally, aor topically depending on whether the preparation is used to treat internal or external viral infections.

For internal infections, the compounds may he administered orally or parenterally in an amount effective to treat the infection. The dosage will, of course, depend on the severity of the infection, but will likely be in the range of ahout 1.0 te 30 mg/kg of hody weight .

For infections of the eve, or other external tissues, e.g., mouth and skin, the compositions may be applied ta the infected part of the bndy of the patient topically as an ointment, cream, aerosol, gel, powder, \ re lotion, suspension or solution (e.g., as eye rors) pnp O — 3 . i . CL + ean

The concentration of the compound in the vehicle will, of course, depend on the severity of the infection, but will likely be in the range of about 0.1 to 7% hy weight. } : The compounds of this invention can be prepared from the known chemical compound 1-chleora-3- (hydroxymethyl )cyclobutane, which is a mixture of cis and trans isomers, Its hydroxymethyl group is first protected using, for example, a silyl containing group (e.g., t-butyldiphenylsilyl), ¢trityl, substituted trityl{(e.g., 4,4'-dimethoxytrityl), or henzyl protecting group. The protection reaction yields a compound of the formula

IT

Ho

H C CHy-0-Prot, \N/ NY

C Cc / NN.

Cl C H

Hy wherein "Prot" stands for a protecting group; i.e., a . . group that protects the hydroxyl group from involvement in suhsequent reactions, This protected cyclobutane is a mixture of cis and trans isomers,

Protection with a benzyl group can he accomplished by treating 1l-chloro-3-(hydroxymethyl)eyeclobutane with . sodium hydride in the presence of henzyl' bromide in a polar aprotic solvent such as dimethylformamide, dimethylsulfoxide or tetrahydrofuran. Protection with =a ‘ t-butyldiphenylsilyl group can be accomplished hy treating a dimethylformamide solution of l-chlore-3- (hydroxymethyl )cyclobntane with t-butyldiphenylsilyl chloride in the presence of imidazole. Protection with 4 BA -~ . ~ -

: a trityl or substituted trityl group can he accomplished hy (i) treating a pyridine solution of 1l-chloro-3- (hydroxymetyl)lecvelobutane with trityl chloride or substituted trityl chloride, (ii) treating a dimethyvlformamide solution of l-chloro-3- (hydroxymethvl)evclabutane with trityl chloride or suhstituted trityl chloride in the presence 4-N,N- dimethylaminopyridine or (iii) treating a dichloromethane solution of l1-chloro-3- (hyvdroxymethyl)eyvelobutane with trityl chloride or substituted trityl chloride in the presence of triethylamine.

Basic elimination of hydrogen chloride from a compound of formula II using a base such as potassium t- butoxide in a polar aprotic solvent, such as dimethyl - sulfoxide or tetrahvdrafuran vields the corresponding compound having the formula . . III

H

C CHy-0O-Prot, 7 N\/ ' .

HC C

N/A . C H

H, as a racemic mixture, Alternatively, =a base such a= lithium diisepropylamide in a solvent such as tetrahydrofuran can he used tao effet the elimination.

Epoxidation of a compound of formula III using a peracid, such as m-rhloroperoxyvbenzoic acid yields the corresponding compound having the formula

L oRIGINA shAD -

Iv

H

Q—C CHy-0O-Prot, 7 \N/ . H-C C

N/A

C H :

Hop as a racemic mixture of cis and trans diastereomers,

Separation of the diastereomers using conventional methodology provides the desired trans sterenisomer having the formula

Vv

H iam CC = / \ CH,-0O-Prot,

H-c of

NN

C H

Ho as a racemic mixture, Alternatively, preferential formulation of the trans epoxide can he achieved hy treating a methanol solution of a compound of formula

III with benzonitrile/30% hydrogen peroxide in the presence of a buffer (e.g., potassium hicarbonate or monohasic patassium phosphate/sodium hydroxide).

Nurleophiliec substitution on the epoxide of a compound of formula V using a nucleophile of the formula

Ry -H, wherein Ry» is

A

0 GINA i gAD OV

TT L

_- N N Xu

A

VII

X2 .

N = N

Y N Xs, or a protected form of a purine base of formula VI or

VII, can he accomplished in the presence of a base, such as sodium hydride or potassium carhonate, in a polar aprotic solvent such as dimethyvlformamide or sul falane.

A complexing agent such as 18-crown-6 ether or 15-crown- § ether can be used in conjunction with the sodium hydride nr potassium carhonate to facilitate nucleophilic substitution on the epoxide. The resulting compound has the formula

VIII ly

C

Prot-0-Ci, Y \ Ry» co cf ' : \N/

C

/%

HOH

Removal of the one, or more, protecting groups from a compound of formula VIII can be accomplished using art- recognized procedures which will depend, of course, on ' the particular protecting group or groups present, anrl vields the products of formula I wherein Ry and R,; are + hydrogen.

Alternatively, compounds of formula I wherein Ry pL ow is

Oo tl (1 ; oN can he prepared hy treating the corresponding compound of formula I wherein Ry is

NH,

Ir ~ ¥ N with adennsine deaminase ar nitrous acid,

The compounds of formula I wherein Ry, is 0 : 1 -C-Xy4 and R, is hvdrogen ar 0

Il —C-Xy can be prepared from the corresponding alcohols using canventional acylation techniques. Compounds of formula

V wherein By is -POoH, (and Ra ie hydrogen) can he prepared from the corresponding alcohols using conventional phosphorylation techniques.

The campounds of formula I wherein Ry, and/or Rg are hydrogen or “ oRGNA- gh» ; _—

Rg

0

I

-C-Xy can form acid-addition salts with inorganic and organic acids, Illustrative are the hydrohalide (e.g., hydrochloride and hydrobromide), alkylsulfeonate, sulfate and phosphate salts. The compounds of formula T wherein

Ry, is -POjH, can form hbasie salts with inorganic and nrganic bases. Tllustrative are alkali metal salts {(e.g., sodium and potassium), alkaline earth metal salts (e.g., calcium and magnesium), ammonium and substituted ammonium salts. : Those compounds of formula I wherein By is 0 i 1 L ( ~<

WAS exist in a tautomeric equilibrium as shown helow: ‘ oO il ; NH

Hi ¢

R;0—H,C ENR Al rh N Xi

JE at

H LC H AE

“, —_—

H OR \ ’ o ORIGINA

BA So oo

OH : : I N mo CL

RO— CHIN Nt N Xi. : | uw” NS “Nk om,

Both of these tautomeric forms are encompassed within the structural formula I.

The stereochemistry shown for the compounds of this invention is relative, not ahsolute. It is drawn "to show that in the compounds of this invention, the purine base (Ry) is cis with respect to the -CH,-0OR, substituent and trans with respect to the OR 4 substituent.

The following examples are specific embodiments of this invention.

EXAMPLE 1 (1a,2Rr,3a)~9-[2-Hydroxy-3-(hydroxymethyl) cyclaobutyl guanine (A) [[(3-Chlaracyclobhutyl)methoxylmethyl lhenzene

A mixture nf 3-chlorncyeclohutanemethannl (17.3 g, 0.143 mole) and henzylbromide (29.96 g, 0.1576 mole) in dry dimethviformamide (123 ml) was stirred at room temperature under an argon atmosphere and a 60% suspension of sodium hydride (6.31 g) was added. The reaction was stirred at ambient temperature for 22.5 hours. The reaction mixture was poured into 600 ml of water and the aqueous mixture extracted with ethyl 1o "apd ore i i i acetate (4X600 ml). The ethyl acetate extracts were combined and dried over anhydrous sodium sulfate and the ethyl acetate evaporated in vacuo yielding the crude product as a yellow oil. The material was puri fied an a 5 . 2-liter Merck silica gel column eluting with 3 liters of hexane, followed by 5% ethyl acetate/hexane. The fractions containing the desired product were combined and the volatiles evaported in vacuo yielding 28.6 g of the title compound as a pale vellow oil. (R) [(2-Cyvclabuten-1-vimethoxylmethyl]lbhenzene [[{(3-Chlorocyclobutyvl )methoxy]lmethyl lhenzene (R2 g, 0.39 male) in 390 ml of dry dimethyvlsulfoxide was slowly added to a solution of potassium t-butoxide (132 g, 1.17 male) in 390 ml of dry dimethylsulfoxide in a water-hath at 18°C under a dry argon atmosphere. After stirring for 1 hour at room temperature, the reaction mixture was poured inta 1600 ml ‘of water and extracted with ether (3X1000 ml). The ether extracts were back- extracted with water (4X2000 ml) and the ether extract wags then dried over sodium sulfate, The ether was removed in vacuo and the crude product was purified on a

Merck silica column, eluting the column with 5% ethyl acetate-hexane. Appropriate fractions were combined and the solvents removed in vacua yielding 60.0 g of the title compound as a colarless liquid. : (Cy (1la,2a,4a)-2-[(Phenylmethoxy)methyl]-5- oxahicyelnl[2.1.0]pentane

A solution of 80% m-chloroperoxyvhenzoic acid (19.0 g, 0.088 mol) in B00 ml of dichloromethane was cooled to 0" c and a solution of [(2-cyclobuten-1- vimethoxy)methyllbenzene (14.0 g, 0.080 mol} was added ¥ ro ore

BA —

and the resulting mixture was stirred overnight at 5°C under an argon atmosphere. The precipitated m- chlorobenzoic acid was removed hy filtration and the } dichloromethane solution was washed with 5% sodium thiosulfate (1X500 ml), saturated sodium bicarhonate (3X500 ml) followed hy washing with water (2X500 ml) and then dried over anhydrous sodium sulfate. The solution was filtered and the dichloromethane was evaporated in vacun vielding 11.6 g¢ of a 1:1 mixture of cis and trans product.

A quantity of the cis and trans isomers (1:1) were separated hy preparative HPLC using =a "Water's Prep 500" with a 500 ml silica gel column eluting with 2.5% ethyl acetate/hexane loading 2 g of mixture at 100 ml/minute and then eluting the column at a flow rate nf 200 ml/minute (tntal 10 g of mixture used). Peak shaving technique was used to enrich one isomer over the other, with the mixture heing recycled through the column 3 times. A total of 2.1 g of trans epoxide and 2.48 g of cis epoxide was separated.

Alternative Separation of Cis and Trans Isomers

A erode mixture of cis and trans epoxide (1:1, 58 g) was isolated from two separate m-chleroeperoxyvbenzoic acid oxidations of two 27.058 hatches of [(2-cyclobuten- 1-ylmethoxy)methyl]lhenzene following the general procedures described above, Twa equal 29 g portions were purified on two separate 3.5 liter silica gel rolumng eluting with 5% ethyl acetate/pentane. The fractions containing essentially pure (ber, 200,340) =-2~- [ (phenylmethoxy)methyl]-5-oxahicycle(2.1.0]pentane were combined and the solvents removed in vacuo yielding 4.02 A 12 Gran : Goo .

g of desired compound. Those fractions containing a greater than 1:1 ratio of trans epoxide were combined an ’ the solvents removed in vacuo vielding 20.58 g of a mixture enriched in trans epoxide.

The trans-enriched mixture was further purified by preparative HPLC using a "Waters Prep 500" equipped with two tandem 500 ml silica gel columns eluting with 5% ethyl acetate/pentane loading 4 g of the mixture at =a time (at a flow rate of 250 ml/minute). A total of 20.5 g of material was loaded in this fashion. Peak shaving technique was used to enrich one isomer over the other, with the mixture being recycled back through the column once, Eventually, A.91 g of essentially pure . (1,2, 4)2-[{phenyvlmethoxy)methyl]-6- oxahicyclo[2.1.0)pentane was isolated in this fashion,

Total recovery was 10,93 g,

Alternative Epexidation Reaction

To a mixture of henzonitrile (0.80 ml, 7.8 mmol) and potassium bicarbonate in 12 ml of methanol was added [{2-cyclobuten-1-yIlmethoxy)methyllhenzene (523 mg, 3.0 mmole) in 12 ml of chloroform followed hy the addition ’ nf 1 ml of 20% hydrogen peroxide, The mixture was rapidly stirred at room temperature under an argon atmosphere for 92 hours. The reaction was poured into 75 ml of 5% sodium thiosulfate and was extracted with 200 ml of ether. The ether extract was washed with 200 ml of water, 200 ml of s2turated sodium hicarhonate and 200 ml of saturated sodium chloride solution. The ether extract was dried over ambydrous sodium sulfate, filtered and the ether removed in vacue yielding 1.1 grams of crude mixture. The crude material was purified

GINA on a 100 ml Merck silica column eluting with A000 ml of hexanes followed by eluting with 1000 ml of 2 1/2% ethyl acetate/hexanes. All fractions containing cis and trans-epoxide were comhined. The volatiles were removed in vacuo vielding 478 mg of a 1:2.5 mixture of cis and trans isomers. (D) (1a,2R8,4R)-2[2-Amino-6-{phenylmethoxy)-9H- purin-9-yll-4-(phenylmethoxy)methyl}- cyclobutanol

Freshly dried (65°C @ 0.1 mm Hg overnight) o- henzylguanine (1.21 g, 5.0 mmol) and 1a ,2¢,40)-2- [ (phenylmethoxy)methyl]l-5-oxahicyclal2.1.0)-pentane (571 mg, 3.0 mmol) were dissolved in 13 ml of dry dimethyl formamide under an argon atmosphere. 60% Sodium hydride (60 mg, 1.5 mmol) was added to the reaction mixture at room temperature and the reaction was, then heated at 110°C for 3 days. The reaction was cooled to ronm temperatnre and the dimethyl formamide was evaporated nnder vacuum at 40°C vielding the crude product as a brown solid. The residue was partially dissolved in 8 ml of dicholoromethane and purified on a 50 ml Whatman LPS! silica column eluting with 1500 ml of dichloromethane followed hy 2000 ml of 2% - methanol/dichloromethane collecting 20 ml fractions. ‘ 25 The fractions containing pure product were combined and : the volatiles removed in vacun yielding the title compound as a colorless solid, 336 mg,

Alternative Reactions

To a stirring suspension of 2 = [(phenylmethoxy)methyl]-5-oxahicyclo[2.1.0]pentane (67.1 mg, 0.30 mmol), o-benzylguanine (121.0 mg, 0.50 mmol, _ oro 14 eh —

dried for 24 hours at 80°C, 1 mm Hg, over P,y0g), and 18- crown-6-ether (61.0 mg, 0.23 mmol) in sulfolane (1.3 ml, ‘ dried over 3A° molecular sieves) at room temperature under argon was added sodium hydride (7.0 mg, 0.1758 5 . mmol, 60% oil dispension). After the mixture was heated to 110°, the solution became homngeneons, After 21 hours at 110%, the reaction was cooled to room temperature and was quenched with acetic acid (25 ml, 0.4 mmol). Most of the solvent was removed hy distillation (0.3 mm Hg) leaving an orange oily residue.

This residue was purified by silica gel chromatography (Merck 230-400 mesh), eluting with CH,oCLg, 1%, 2%, and then 3% MeOM: CH: CHyCL, to give the pure coupled product (54.8 mg). (E) (12, 28,3) -9-[2-Hydroxy-3-(hydroxymethyl) cyclobutylgnanine (1a,28,4B)-2-[2-Aminn-f-{phenylmethoxy)-9H-purin-

A-yl}-4-[(phenvimethoxy)methyl Jeyclahutannl (336 ne, 0.78 mmol) in 3 ml of dry, distilled tetrahydrofuran was added to 30 nl of liquid ammonia at -78°C under an argon atmosphere, With stirring, finely cnt sodium (165 mg, f.9 mmol) was added and when the mixture hecame dark blue in color the cooling bath was removed and the mixture was allowed to stir for 10 minutes, The . reaction was quenched by adding small portions of ammonium chloride until the reaction hecame colorless.

The volatiles were next removed by allowing a slow stream of nitrogen to pass through the reaction mixture vielding the crude product as a colorless solid. The crude solid was dissolved in 20 ml of water and the pH was adjusted from pH 12.6 to pH 7.0 by adding 1 N WA

ORC hydrochloric acid solution. When the pH reached pH 10 the product hegan to precipitate from solution. The

SL precipitated product was collected by rentrifugation and ’ was washed twice with cold water (2X4 ml). The resulting colorless solid was dried in vacuo avernight at room temperature yielding 134 mg of the title product, melting point 2467 (dec),

Anal. Cale’d. for CoH 3NgR3+1.25H,0: C, 43,74;

H, 6.72; N, 25.51, Found: CC, 43,43; H, 5.53; N, 25.8213,

EXAMPLE 2 (1a,20,3a)~-2-(6-Amino-9H-purin-9-v1)-2-hydroxy- cvclabutanemethanel (A) (1, 20,4) -2~(2-Amino-9H-purin-9-yl)-4- [ {(phenylmethoxy)methyl Jeyclobutanol

A mixture of dried adenine (557 mg, 4.125 mmol) and (laa ,2ca 4c )2-{(phenvlmethoxy)lmethyl]-6- axahicyecln[2.1.0]lpentane (523 mg,” 2.75 mmol; see example 1¢) was partially dissolved in 5.5 ml of dry dimethylfearmamide under an argon atmosphere, To this mixture was added potassium carhanate (95 mg, 0.69 mmol) - . fallawed hy 18-crown-6 ether (330 mg, 1.25 mmol) and then the mixture was heated at 1109C for 60 hours. The reaction was conled to room temperature, and the volatiles were removed under vacuum at 40°C vielding the crude product as a hrown solid. The residue was partially dissolved in 10 ml of dichloromethane and purified on a 250 ml Whatman LPSI1 silica gel column, eluting with 750 ml of dichloromethane followed hy 2000 mL of 2 1/2% methannl/dichloromethane. The fractions containing the pure desired product were comhined and the volatiles removed in vacuo yielding the title QIGINA- oro

-— EE — compound as a colorless solid, 212 mg. (BR) (1a,2R, 32) -3-(6-Amino-9H-purin-9-yl)-2- hydroxycyeclobutanemethannl (1a,28,4a)-2-(2-Amino-9H-purin-9-y1)-4- [ (phenylmethoxy)methyl]leyelohutanol (200 mg, 0.615 mmol) : was dissolved in 40 ml of absolute ethanol and 20 ml of cyclohexane, 20% Palladium hydroxide (140 mg) was added and the mixture was heated at reflux far 66 hours. The reaction was filtered through a "milipore”" filter to remove the catalyst and the catalyst was washed with approximately 10 ml of ethanol. The volatiles were removed in vacuo yielding the crude product as a colorless solid. The material was dissolved in 5 ml of water and purified on a 50 ml HP-20 column eluting with a 600 ml 50% acetonitrile-water/water gradient. The fractions containing pure product were comhined, the acetonitrile removed in vacuo and the water lyophilized to vield 59 mg of product sas a colorless solid, melting point 2407 (dec),

BAD ORG

Claims (1)

9 6 () >» : id 7 il CLAIM

1. A compound having the formula H - Quin CHy-0-Prot “SAT H-C © \ ON C H Hoy wherein Prot is a hydroxyl protecting group. Inventars: ROBERT ZAHLER . GLENN A. "JACOBS \ \GINA BR Or — 1R j

J ft fw ARSTRACT Disclosed are compounds having the formula H Co Q C CHy~0-Prot / NN! ! H-C C N/A Cc H : Hy wherein Prot is a hydroxvl protecting group. a The compounds are usefyl as intermediates in the preparation of compounds of the formula Hy \N/ NT C Cc : N/A H C H / H ORq which in turn are useful as antiviral agents, r AL 1GIN

} . BAD OR