GB2168704A - 1-(tetrazol-5-ylphenyl)-2-(tetrazol-5-ylalkylthio) alcohols and their use as leukotriene antagonists - Google Patents

Abstract

Compounds of the formula <IMAGE> in which R<1> is C7-20 alkyl or C7-20 alkenyl containing 1 to 3 double bonds, R<2> and R<3> are each hydrogen and X is C1-6 alkylene; and salts thereof are leukotriene antagonists. Compounds of formula (I) in which R<2> and R<3> are each hydrogen or a protecting group are also described and are useful as intermediates in the preparation of the pharmaceutically active compounds.

Description

1 GB2168704A 1

SPECIFICATION

Novel organic compounds and their pharmaceutical use This invention relates to novel compounds and their use as pharmaceuticals. 5 The compounds of the invention are of the formula N R 1 -CH=CH-CH-CH(OH) N NI (1) 10 R 3 10 11 1 -X-'N R2 15 15 in which R' is C,,, alkyl or C7,, alkenyl containing 1 to 3 double bonds, R2 and R3 are each hydrogen or a protecting group, and X is C,, alkylene; and salts thereof.

The compounds of the invention, with the exception of compounds in which R2 or R3 is a protecting group which are intermediates in the preparation of the remaining compounds, have been shown to be pharmacologically active in tests which demonstrate their antagonist effect on 20 leukotriene receptors and indicate their use in the treatment of allergy disorders.

In the above general formula, R' can be an alkyl group containing from 7 to 20 carbon atoms, and is preferably alkyl containing from 8 to 13 carbon atoms, such as for example 10 to 13 carbon atoms. The alkyl group is preferably straight chained. When R' is alkenyl it contains from 25 7 to 20 carbon atoms and preferably from 8 to 13 carbon atoms, such a for example 10 to 13 25 carbon atoms. Preferably the alkenyl group is unbranched and contains 1 or 3 double bonds.

Particularly preferred alkenyl groups are those of formula R 4CH=CH- where R4 is C,-, alkyl or CHACI-1j,Cl-l=CHCH2CH=CH2_.

It will be appreciated that such double bonds, and the double bond between the 3 and 4 30 carbon atoms, provide opportunities for cis-trans isomeric forms. It is preferred that the R' group 30 is arranged in trans configuration about the double bond at the 3 and 4 carbon atoms. It will also be appreciated that the compounds of formula (1) possess chiral centres at the carbon atoms bearing the hydroxyl and thio groups and, accordingly, stereoisomeric forms exist R,R; S,S; R,S; and S,R. All such stereoisomers, and racemic mixtures thereof, are included within the 35 scope of the invention. The preferred compounds are of S,R configuration. Isomers can be 35 isolated from racemic mixtures by conventional methods such as by the preparation of diastereo isomers with subsequent liberation of the enantiomers or, alternatively, can be prepared by methods devised to give the pure isomer.

Examples of particularly preferred groups are those in which the moiety RICH=CH in formula 40 (1) above is 40 CH 3 (CH P7CH 2 /- \==\ 45 45 and 50 50 The -X- group in formula (1) above is an alkylene group containing 1 to 6 carbon atoms which can be branched or unbranched and is preferably of the formula -(CH, ).- where m is 1, 2, or 3.

55 When R2 or R3 is a protecting group it can be any of the well known protecting groups 55 employed for the purpose of protecting the tetrazolyl radical and such groups include optionally substituted trityl and benzhydryl, and optionally substituted benzyi for example p-methoxybenzyl, or a sily] group for example t-butyidiphenyisiiyi. The preferred intermediates are those in which R2 is hydrogen and R3 is a protecting group. As is well known the tetrazolyl group exhibits 60 tautomerism and the position of attachment of the protecing group will depend on its size, 60 though generally the point of attachment is at the 2-position.

The compound of formula (1) bears either one or two acidic functions, depending on whether the R2 or R3 substituent is a protecting group or hydrogen. In the latter case the free tetrazolyl groups provide two acidic functions. Base addition salts of these compounds can thus be 65 prepared and these are included as part of the present invention. Examples of such salts are 65 2 GB2168704A 2 those derived from ammonium hydroxide and alkali and alkaline earth metal hydroxides, carbonates and bicarbonates, as well as salts derived from aliphatic and aromatic amines, aliphatic diamines and hydroxy alkylamines. Bases especially useful in the preparation of such salts include ammonium hydroxide, potassium carbonate, sodium bicarbonate, calcium hydroxide, methylamine, 5 diethylamine, ethylene diamine, cyclohexylamine and ethanolamine. The potassium and sodium 5 salt forms together with other pharmaceutically acceptable salts are particularly preferred, but it is to be understood that other non-pharmaceutical salts are involved in the invention since they may be useful for identification, charactisation or purification of the free compound.

A particular group of compounds according to formula (1) above are those of the formula 10 10 H " CH N::,w - 2 " I I - I 11 CH (CH) CH I ' ' N 'Q 3 2 7 2. / H 0 .0 p3 15 15 N S (CH 2)m-qj H 20 in which R3 is hydrogen or a protecting group and m is 1, 2 or 3; and salts thereof. Such 20 compounds exhibit 1S, 211 chirality.

The invention also includes a process for producing a compound of general formula (1) which comprises reacting a compound of formula 25 'N 25 R i-.10, 1 (11) MCH-CH- CH N 0 N 3 R 30 30 in which R' is as defined above and R-1 is a protecting group, with a thiol of formula N _ N HS-X< ' 1 (111) 35 N 35 R2 in which R2 is hydrogen or a protecting group, optionally followed by removal of the R2 or R3 protecting group. The reaction is generally carried out in the presence of a base, preferably a 40 strong base such as potassium t-butoxide in an organic solvent such as for example t-butanol at 40 a temperature of from O'C to 60'C.

Intermediate compounds of formula (11) may be prepared by the Wittig reaction of a phosphonium salt of formula R4CH2PPh3Br, R4 being an appropriate alkyl or alkenyl group, in the presence of a base such as butyl lithium, with an aldehyde of formula (IV) or (V) 45 45 OHC N - OH 0 N N N h N 2 R R 2 50 50 (M M I R 4 CH,PPh 3 Br- I R 4 CH 2 PPh 3 Sr 55 55 N 0 I R 4//7 N R 4'' 1 2 2 60 60 where R2 is a protecting group. The reaction is generally carried out in an inert organic solvent such as for example, tetrahydrofuran, at a temperature of from - 11 OOC to OOC.

Compounds of formula (IV) may be prepared from known intermediates by, for example, two principal routes. Firstly, they may be prepared, as racemic mixtures, by oxidation with, for 65 3 GB2168704A 3 example, aqueous hydrogen peroxide and sodium hydrogen carbonate in methanolic solution, of an aldehyde of the formula N N OHC 1 5 N R 2 10 in which R2 is a protecting group and, in its turn, the aldehyde of formula (N) may be converted 10 to one of formula (V) by reaction with formyimethylenetriphenylphosphorane.

Alternatively, the compounds of formula (IV) may be prepared by oxidation of an epoxy alcohol of the formula 15 0 N Z-14 15 HO <' 9,1 (VI) o R2 20 with an oxidising agent such as, for example, chromium trioxide in pyridine. Compounds of 20 formula (V1) can be prepared in stereospecific form, the steric configuration being retained on oxidation to provide the aldehyde of formulae (R) and, ultimately, of formula (V).

Compounds of formula (V1) are prepared from the allyl alcohol 25 N -, % 25 1 N HO N (V1 1) R 2 W P 30 using as epoxidising agent a reagent such as titanium isopropoxide-t- butyl hydroperoxide in the 30 presence of L or D diethyl tartrate which yields the S,S or R,R epoxide with the above E olefin.

When the Z olefin is used as starting material, the appropriate S,R and R, S stereoisomers result.

Compounds of formula (V11) can be prepared from the appropriate benzaldehyde via a sequence of reactions involving reaction with malonic acid to provide the cinnamic acid derivative, treat- 35 ment with oxaly] chloride to give the acid chloride, and reduction with a reagent such as lithium 35 tri-t-butoxyaluminohydride. The Z olefin is produced by catalytic reduction using a Lindlar catalyst of the appropriate acetylenic derivative.

Compounds of formula (111) can be prepared from the appropriate compound of formula Br-X-CN by reaction with benzy] mercaptan to give a benzyithio nitrile which, in its turn, can be converted with azide and ammonium chloride to the corresponding tetrazolyl derivative from 40 which the compound of formula (111) is liberated by treatment with sodium in liquid ammonia. A preferred method of making the compound in which -X- is -(C1-1j,- is from acrylonitrile as starting point using the Michael reaction.

The following scheme shows how compounds of the invention may be prepared (R5 stands for 45 the group 45 N R 2 _ W N- GB2168704A 4 H -0 30 (j o 0.o H H 1" 1 i H W R 5 0.

Co 2 H H \C 1 '0', '0 p 5 0 W 9) OH "'4 R5 e', E 5 0 il H /1 (h, o M' 5 0 H3 R 35 p' i R 5 R '_.0 - R 5 : VIl i - li (k., S 1 X- C I 021 (L-> 5 o 5 R 0-1 Key:

(a) reaction with malonic acid in pyridine and piperidine.

(b) reaction with oxalyl chloride in ether (C) reaction with formylmethylenetriphenylphosphorane in toluene (d) reaction with lithium tri-t-butoxyaluminohydride in tetrahydrofuran (e) reaction with aqueous hydrogen peroxide and sodium hydrogen carbonate in methanolic solution (f) reaction with sodium borohydride in methanol (g) reaction with manganese dioxide in dichloromethane (h) reaction with chromium oxide in pyridine (i) reaction with titanium isopropoxide t-butyl peroxide in dichloromethane and L-cliethyl tartrate 0) reaction with RICH,P,Ph,Br in the presence of butyl lithium and in tetrahydrofuran as solvent (k) reaction with thiol of formula (111).

The compounds of the present invention are pharmacologically active, being leukotriene anta gonists as shown by the in vitro test on guinea pig ileum segments at a concentrations of from 55 1 ng/ml to 50 ug/ml, according to the method of Schild (1947) Brit. J. Pharm. 2, 197-206 (the unprotected compounds of formula (1) described in the following Examples exhibited an IC,, against LTD, of less than 10-5 molar). Also compounds of the invention are active in the in vivo Guinea Pig Pulmonary Function Test of Austen and Drazen (1974) J. Clin. Invest. 53 1679-1685 60 at intravenous dosage levels of from 0.05 ug/kg to 5.0 mg/kg and in a modified "Herxheimer" 60 test (Journal of Physiology (London) 117 251 (1952)) at doses of from 25 to 200 mg/kg. The "Herxheimer" test is based on the LTD 4-induced bronchospasm in guinea pigs which closely resembles an asthmatic attack in man. The compounds also show low bronchial irritancy.

The compounds are accordingly indicated for therapeutic use in the treatment of diseases in which leukotrienes are implicated. These include allergic reactions of the pulmonary system in 5 GB2168704A 5 which leukotrienes are thought to be causal mediators of bronchospasm, for example, in allergic lung disorders such as extrinsic asthma and industrial asthmas such as Farmers lung and Pigeon Fanciers lung, and in other inflammatory disorders, for example, associated with acute or chronic infectious diseases such as allergic skin diseases, ectopic and atopic eczemas, psoriasis, contact 5 hypersensitivity and angioneurotic oedema, bronchitis and cystic fibrosis and rheumatic fever. 5 Thus the invention also includes a pharmaceutical composition comprising a pharmaceutically acceptable diluent or carrier in association with a compound of formula (1) in unprotected form; or a pharmaceutically acceptable salt thereof.

The compounds may be administered by various routes, for examples by the oral or rectal 10 route, topically or parenterally, for example by injection, and especially by inhalation, being 10 usually employed in the form of a pharmaceutical composition. Such compositions are prepared by a manner well known in the pharmaceutical art and normally comprise at least one active compound. In making the compositions of the present invention, the active ingredient will usually be mixed with a carrier, or diluted by a carrier, and/or enclosed within a carrier which may, for 15 example, be in the form of a capsule, sachet, paper or other container. When the carrier serves 15 as a diluent, it may be a solid, semi-solid, or liquid material which acts as a vehicle, excipient or medium for the active ingredient. Thus, the composition may be in the form of tablets, lozenges, sachets, cachets, elixirs, suspensions, aerosols (as a solid or in a liquid medium), ointments containing for example up to 10% by weight of the active compound, soft and hard gelatin 20 capsules, suppositories, injection solutions and suspensions and sterile packaged powders. For 20 administration by inhalation, particular forms of presentation include aerosols, atomisers and vaporisers.

Some examples of suitable carriers are lactose, dextrose, sucrose, sorbitol, mannitol, starches, gum acacia, calcium phosphate, alginates, tragacanth, gelatin, syrup, methyl callulose, methyl 25 and propylhydroxybenzoate, talc, magnesium stearate and mineral oil. The compositions of the 25 invention may, as is well known in the art, be formulated so as to provide quick, sustained or delayed release of the active ingredient after administration to the patient.

Where the compositions are formulated in unit dosage form, it is preferred that each unit dosage form contains from 5 mg to 500 mg, for example, from 25 mg to 200 mg. The term 30 "unit dosage form" refers to physically discrete units suitable as unit dosages for human 30 subjects and animals, each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect, in association with the required pharmaceutical carrier.

The active compounds are effective over a wide dosage range and, for example, dosages per day will normally fall within the range of from 0.5 to 300 mg/kg, more usually in the range of 35 from 5 to 100 mg/kg. However, it will be understood that the amount administered will be 35 determined by the physician in the light of the relevant circumstances including the condition to be treated, the choice of compound to be administered and the chosen route of administration, and therefore the above dosage ranges are not intended to limit the scope of the invention in any way.

40 The invention is illustrated by the following Examples. The structure of the compounds pre- 40 pared was confirmed by I.R. and/or n.m.r. and/or mass spectra.

EXAMPLE 1 (A)(i) 3-(Benzylthip)-propionitrile 45 Acrylonitrile (21.4 g, 0.4 M) was added dropwise to a solution of benzyl mercaptan (49.6 g, 45 0.4 M) and triethylamine (4 m1s) in methanol (400 m1s). This addition lead to an exothermic reaction and the temperature of the reaction mixture was allowed to rise from room temperature to 35oC. After 10 minutes the reaction was almost complete as shown by TLC, there being a trace of unreacted thiol still present. Additional acrylonitrile (0.5 g) was then added to consume 50 the last of the thiol. After a further 10 minutes the solution was evaporated to give the title 50 compound 69.0 g as a pale yellow oil.

(ii) 5-[2-(Benzy1thio)-ethy1]- 1H-tetrazole A mixture of 3-(benzylthio)-propionitrile (33.30 g), sodium azide (61.14 g) and ammonium 55 chloride (50.33 g) in dry dimethylformamide (220 m1s) was stirred at 120' for 20 hours. 55 Additional sodium azide (24.50 g) and ammonium chloride (20.13 g) was then added, and heating at 120' continued for further 6 hours.

The cooled reaction mixture was poured into a mixture of ice/water and 2 molar hydrochloric acid and extracted with dichloromethane. The organic extracts were in turn extracted with ten per cent sodium carbonate solution, and the basic extracts cautiously acidified with concentrated 60 hydrochloric acid. The resulting precipitate was collected by filtration, washed with water, and dried in vacuo to give the required product as a white solid (28.95 g), m. p. 80-82C.

(iii) 5-(2-Mercaptoethyl)- 1H-tetrazole 65 5-[2-(Benzylthio-ethylj-lH-tetrazole (15.00 g) was added portionwise as a solid to a solution of65 6 GB2168704A 6-- sodium metal (7.84 g) in liquid ammonia (2-300 mls). The reaction mixture was stirred at 20 under a drying tube (silica gel) for 2 hours and then very cautiously quenched with methanol (100 mls). The excess ammonia was removed under a nitrogen stream and the residue acidified with hydrochloric acid and extracted with ethyl acetate. The organic extracts were dried over magnesium sulphate, filtered and evaporated under reduced pressure to yield the title compound 5 as a white solid (7.15 g), m.p. 104-1060C.

(B)(i) (3-Cyanocinnamoyl chloride) 3-Cyanocinnamic acid (200 9) was treated with diethyl ether (3333 mi), oxaly] chloride (100.8 10 mi) and dimethyl formamide (2 mi) and stirred at room temperature for 5.5 hours in a vessel 10 closed by a silica tube. The solution was decanted from insoluble material and evaporated to dryness to leave a pale yellow to white solid, which was dried at 40- 50"/high vacuum to give the acid chloride, melting point 1OWC.

(ii) (3-Hydroxy-l-propenyi)benzonitrile 15 NaBH,7A1201 (1219 9) (prepared according to Santaniello, Ponti and Manzocchi, "Synthesis',, 1978, 891, but using Woelm Alumina N instead of the type specified: the reagent formed contained 2.04 M.mole of NaBH, per gram) was stirred in diethyl ether (6340 m]) at room temperature and the acid chloride (200 g) from (B)(i) in ether (7800 mi) was added dropwise 20 during one hour. The temperature rose from 20-27', and had fallen to 26 one hour after 20 completion of the addition. The mixture was stirred for a total of 1.5 hours after completion of the acid chloride addition. The alumina was filtered off and washed with ether (3X2 1), the filtrate was evaporated to dryness to leave an oil which solidified on storage in a refrigerator.

The solid alcohol had a melting point <500C.

25 25 (iii) 3-(5Tetrazolyl)cinnamyl alcohol 3-Cyanocinnamyl alcohol (292.97 g), dimethylformamide (914 mi), triethylamine hydrochloride (558.7 g) and sodium azide (358.85 g) were added to a flask. The reaction was carried out under nitrogen and after addition of all the reactants heat was applied. The temperature of the 30 reaction mixture reached 1OWC 1-2 hours after commencement of heating and the solution was 30 stirred and heated at 100' for 8 hours. The solution was transferred to a 10 litre flask, treated with water (2944 mi), stirred and cooled to MC (ice-bath), treated with concentrated HCI (736 m]) and stirred for 2.5 hours while the temperature dropped from 20' to WC. The solid was filtered washed with cold water (3 X 21---and 1 X 1 L) and dried, initially for 1.5 hours in a fluid 35 bed drier, then at W/high vacuum to give 3-(5-tetrazoiyi)cinnamyi alcohol, melting point 174'C. 35 (iv) (E) 3-[3-(2-Triphenyimethyl-2H-tetrazol-5yl)phenyll-2-propenol To a solution of 3-[3-(1H-tetrazol-5-yi)phenyll-2-propenol of (iii) above (2.02 g) in dry dichloromethane (50 mi) was added triethylamine (1.5 mi) followed by triphenylchloromethane (2.8 g) in 40 dry dichloromethane. The solution was stirred at room temperature for 90 minutes, washed with 40 water (50 m]) followed by sodium bicarbonate solution (5%; 50 mi), dried over magnesium sulphate, filtered and evaporated under reduced pressure to give a pale brown viscous oil which crystallised on standing to a cream solid.

(v) (2S,3S)-3-[3-(2-Triphenyimethyl-2H-tetrazol-5-yl)phenyl]2,3epoxypropanol 45 L-(+)-Dimethyl tartrate (1.85 9) was added in dry dichloromethane (10 mi) dropwise to a stirred solution of titanium (IV) isopropoxide (3.1 mi) in dry dichloromethane (30 m]) at -20 to -25'C under nitrogen. The solution was stirred for 10 minutes and a solution of 3-[3-(2 triphenylmethy]-2H-tetrazol-5-yi)phenyll-2-propenol (4.5 9) in dry dichloromethane (20 mi) was 50 added, followed by a 3.7 M solution of t-butylhydroperoxide in toluene (6.7 mi), both at -20 to 50 -25'C. The pale orange solution was left to stand in a freezer for 3 hours. To the stirred solution was added aqueous tartaric acid (10%; 50 mi) and the mixture stirred for 1 hours, filtered and separated. The dichloromethane layer was dried over magnesium sulphate filtered and evaporated under reduced pressure to give a yellow oil. The oil was dissolved in carbon 55 tetrachloride, washed with water, dried over magnesium sulphate, filtered and evaporated under 55 reduced pressure to give a pale yellow oil. The oil was chromatographed on a silica gel column using diethyl ether and hexane (2:1) and the required fractions evaporated under reduced pres sure to give a colourless crystalline solid.

(vi) (4S,5S)-5-[3-(2-Triphenylmethyl-2H-tetrazol-5-yl)phenyll-4,5-epoxy-2pentena l 60 Solid chromium trioxide (5.0 g) was added to a stirred solution of pyridine (7.9 mi) in dry dichloromethane (200 mi) at 5'C. The mixture was stirred for 45 minutes, warming to 13'C, allowing all the chromium trioxide to dissolve, then a solution of the epoxyalcohol of step (ii) (4.61 9) in dry dichloromethane (50 mi) was added rapidly. The dark mixture was stirred for 90 minutes. warming to room temperature, then filtered through a pad of Florisil (RTM) to remove 65 7 GB2168704A 7 the chromium salts, and the colourless filtrate was evaporated under reduced pressure to leave a pale yellow oil.

To a solution of the oil (1.8 g) in benzene (75 mi) under nitrogen, was added formyimethylen etriphenylphosphorane (1.34 9) in one portion. The suspension was stirred at room temperature 5 under nitrogen for eight hours, unreacted ylid was filtered off and the filtrate evaporated under 5 reduced pressure to a brown oil. The brown oil was extracted with hot ether, cooled, filtered and evaporated under reduced pressure to give a yellow oil, which crystallised on standing to give a yellow solid.

10 (vii) (1S,2S)-5-R[3-[2-(1,2-Epoxy)pentadeca-3(E),5(Z)-dienyllphenyll-2triphenyime thyl-2H-tetrazole 10 n-Butyl lithium (8.91 mi; 1.5 M) in hexane was added dropwise to a stirred solution of n-decyl triphenylphosphonium bromide (6.07 9) (dried at 8WC under reduced pressure for 16 hours) in dry tetrahydrofuran (130 mi) at -70'C under nitrogen. The clear deep orange solution obtained was stirred for a further 10 minutes at -70'C, then a solution of 5-[3-(2- triphenyimethyi-2H 15 tetrazol-5-yi)phenyll-4,5-epoxy-2-pentenal (6.4 g) in dry tetrahydrofuran (75 mi) was added 15 dropwise. The pale yellow solution was stirred at -70C for 1 hour, allowed to warm to room temperature and evaporated under reduced pressure to a brown oil. The oil was extracted with ether:hexane (12; 4X200 mi) and the pale hazy extract evaporated under reduced pressure to give the title compound as a yellow oil.

20 20 (1S,2R)-5-[3-[2(2-(1H)-Tetrazol-5-ylethyithio)1-hydroxypentadeca-3(E), 5(Z)-dienylphenyll-2triphenyimethyl-2H-tetrazole 5-(2-Mercaptoethyi)-1H-tetrazole (73 mg, 0.5 mM) was dissolved in dry tertiary butanol (2 m]) under nitrogen at room temperature. Potassium tertiary butoxide (112.2 mg, 1.0 mM) was added 25 and the resultant suspension stirred at room temperature for 10 minutes. This suspension was 25 then added to (1S,2S)-5-13-[2-1,2-oxido)pentadeca-3(E),5(Z)dienyllphenyll-2-triphenyimeth yl-2H- tetrazole also under nitrogen and the resultant mixture stirred at room temperature for 6 hours.

Water 10 mi was then added and pH of the solution adjusted to 7 with acetic acid. This aqueous solution was then extracted 3 times with dichloromethane and the combined extracts 30 evaporated to dryness. The resultant colourless oil was chromatographed on a silica column 30 eluted with ethyl acetate. The title compound was obtained chromatographically pure as a colourless oil, yield 55 mg.

(ii) (1S,2R)-5-1'3-[2-(2-1H-Tetrazol-5-ylethylthio)-1-hydroxypentadeca3(E),5(Z)-d ienyllphenyll-1H- 35 tetrazole, di sodium salt 35 (1S,2R)-5-13-[2-1H-Tetrazole-5-yiethyithio)-1-hydroxypentadeca-3(E),5(Z)die ny1]phenyll-2-triphe- nyimethyi-2H-tetrazole (30 mg) was dissolved in ether (1 mi), Water (1 mi) and 98/100 formic acid (0.5 mi). The resultant solution was stirred at room temperature for 6 hours. The pH of the reaction mixture was then adjusted to 9 using sodium carbonate and extracted three times with 40 ether. The pH of aqueous was then adjusted to 3 using hydrochloric acid and extracted three 40 times with ether. The combined ether extracts were dried and evaporated to yield the free acid of the title compound, yield 12 mg. This was converted to a solution of the disodium salt by reaction with aqueous sodium bicarbonate.

45 EXAMPLE 2 45 This Example illustrates a further preparation of the compound of Example 1C(ii) above, and the isolation of its 3(E), 5(E) isomer.

(i) (1S,2R)-5-13-[2-(2-(1H)-Tetrazol-5-ylethylthio)-1-hydroxypentadeca3(E)15(Z) -dienyll-2-triphenyl- 50 methyketrazole. 50 5-(2-Mercaptoethyi)-1H-tetrazole (1.469) was dissolved in dry tertiary butanol (15mi) under nitrogen at room temperature. Potassium tertiary butoxide (2.249) was added and the resultant suspension stirred at room temperature for 10 minutes. This suspension was then added to (1S,2S)-5-13-[2-1,2-oxido) pentadeca-3(E),5(Z)-dienyi]phenyl-2triphenylmethyl-tetrazole (1.2169) 55 also under nitrogen and the resultant mixture stirred at room temperature for 20 hours. The 55 solvent was then removed under reduced pressure and water (120mi) added, the resultant solution extracted twice with hexane/diethyl ether 50/50 to remove non- acidic non polar impuri ties. The pH of the aqueous solution was then adjusted to 3 using 2M hydrochloric acid and the suspension extracted five times using diethyl ether. The combined diethyl ether extracts were 60 concentrated to a total volume of 15mi and this solution of the title compound used in the next 60 experiment.

(ii) (1S,2R)-5-[3-[2-1H-Tetrazol-5-ylethylthio)-1-hydroxypentadeca-3(E), 5(Z)-dien yilphenyll-1H-tetra- zole.

65 The solution of (1S,2R)-5-13-[2-(2-1H-tetrazole-5-yiethyithio)-1hydroxypentadeca-3(E),5(Z)-d ieny- 65 8 GB2168704A 8 1]phenyll-2-triphenyimethyi-tetrazole (1 5mi) from the previous experiment was stirred under nitro gen. Formic acid 98% (5mi) and water (5mi) were added and the solution stirred for a further 6 hours at room temperature. The diethyl ether was then removed under reduced pressure and solid sodium carbonate added to the aqueous solution until the pH was 10. Additional water 5 (15mi) was then added and the triphenyl carbonate removed by filtration. The aqueous solution 5 was then extracted once with diethyl ether and the pH then adjusted to 3 using 2M hydrochloric acid and extracted five times using chloroform. The combined chloroform extracts were evapo rated to dryness to yield the crude product (1.59) as an oil.

The oil was then purified by reverse phase high performance liquid chromatography using a 2.5X50cm C18 column eluted with methanollwater:80/20 0.1% acetic acid, the material being 10 processed as ten equal aliquots. The major product was the title compound which after evapora tion of the solvent and recrystallization from diethyl ether was obtained as white crystals, mp 100-103'C.

The E,E isomer of title compound was obtained as an impurity which eluted as a separate 15 peak of marginally greater retention time than the title compound. 15 On evaporation of the solvent (1S,2R)-5-13-[2-(2-1H-tetrazol-5- ylethylthio)-1-hydroxypentadeca3(E),5(E)-dienyl]phenyfl-1H-tetrazole was obtain as a pale yellow oil.

EXAMPLE 3

20 (A)(i) 2-(Benzylthio)-acetonitrile 20 To a stirred solution of benzylthiol (27.289) in ethanol (50mi) under nitrogen was added, dropwise with cooling, triethylamine (22.29), then sodium iodide (339). After stirring this mixture at room temperature for fifteen minutes, a solution of chloroacetonitrile (16.6g) in ethanol (50mi) was added dropwise, with ice-bath cooling. The reaction mixture was stirred at room tempera 25 ture, under nitrogen, overnight. 25 The reaction mixture was filtered through Hi-Flow (HYFLO is a RTIVI) and the filtrates evapo rated in vacuo to give a gelatinous residue, which was partitioned between water (200mi) and diethyl ether (2X100mi). The ether extracts were washed with 2M sodium carbonate (2X100mi) and saturated brine (2X100mi), dried over magnesium sulphate and evaporated in vacuo to give 30 the title compound as a nearly colourless oil (32.549). 30 The following compound was simularly prepared 4-(Benzyithio)- butyronitrile b.p.

172-174'C/mmHg.

(ii) 5-(Benzylthiomethyl)- 1H-tetrazole 35 A mixture of 2-(benzylthio)-acetonitrile (32.329), sodium azide (64. 449) and ammonium chloride 35 (53.049) in dry dimethylformamide (300mis) was stirred at 1OWC for sixteen hours. The reaction mixture was allowed to cool and then poured into an ice/water

mixture (11) previously acidified to pH2 with 2M hydrochloric acid. The off-white precipitate was collected by filtration, washed with more water on the sinter, and dried in vacuo at WC to give the product 40 as an off-white solid (29.59), m.p. - 1OWC. 40 The following compound was simularly prepared 5-(3-Benzyithiopropyi)-1H- tetrazole, an oil.

(iii) 5-(Mercaptomethyl)-1H-tetrazole To a stirred solution of sodium metal (9.99) in liquid ammonia (about 400mis) was added 5 45 (benzyithiomethyi)-1H-tetrazole (29.59). The reaction mixture was stirred at room temperature for 45 two hours and then cautiously quenched with methanol (150mi) (effervescence). After removing excess ammonia with a fast nitrogen stream the reaction mixture was acidified with concentrated hydrochloric acid and extracted three times with ethyl acetate. The extracts were dried over magnesium sulphate and evaporated in vacuo to give a solid residue which, after washing with 50 hexane, gave the title compound as a white fluffy solid (9.19), m.p. 74-76"C. 50 The following compound was simularly prepared 5-(3-Mercaptopropyi)-1H- tetrazole, an oil.

(B) The intermediates synthesised in (A)(iii) above were used to prepare the following end products by the methods described in Example 1: (1S,2R)-5-1-[2(2-1H- Tetrazol-5-yimethyithio)-1hydroxypentadeca-3(E),5(Z)-dienyllphenyil-1H-tetrazole, a yellow oil.

55 (1S,2R)-5-1t-[2-(2-1H-Tetrazol-5-yipropy[thio)-1-hydroxypentadeca-3(E), 5(Z)-dienyllphenyil-1H-tet- 55 razole, a yellow oil.

The active compounds of the invention are preferably employed in salt form. The following formulations are given by way of example:

60 EXAMPLE 4 60 Soft gelatin capsule Each soft gelatin capsule contains:

9 GB2168704A 9 Active ingredient 150 mg Arachis oil 150 mg 5 After mixing together, the blend is filled into soft gelatin capsules using the appropriate 5 equipment.

EXAMPLE 5

Hard gelatin capsule Each capsule contains 10 Active ingredient 50 mg PEG 4000 250 mg 15 The PEG 4000 is melted and mixed with the active ingredient. Whilst still molten the mixture 15 is filled into capsule shells and allowed to cool.

EXAMPLE 6

Aerosol 20 20 Active ingredient 10 mg Ethanol 50 mg Dichlorodifluoromethane (Propellant 12) 658 mg Dichlorotetrafluoroethane (Propellant 114) 282 mg 25 25 The active ingredient is dissolved in the ethanol. The concentrate is filled into extruded aluminium cans for inhalation aerosols. The cans are degassed with propellant 12 and sealed with an appropriate metered dose valve. The volume of product expelled per actuation is 50 or 100 pi equivalent to 0.5-1 mg active ingredient.

30 30

Claims (10)

1. A compound of the formula N 35 35 R -CH=CH-CH-CH(GH) N N R3 N zzzw i N N 5-X 1 1 RN'N 40 R2 40 in which R' 'S C7-20 alkyl or C,,o alkenyl containing 1 to 3 double bonds, R 2 and R 3 are each hydrogen or a protecting group, and X is C,, alkylene; or a salt thereof.

2. A compound according to claim 1 in which R2 and R3 are both hydrogen.

45

3. A compound according to claim 2 in which R' is of the formula R 4 CH=CH- where R4 is 45 C,-, alkyl or CHACHICH=CHCH2CH=CH2_.

4. A compound according to claim 3 in which RICH=CH in formula (1) is 50 50 CH 3 (CH P7 CH 2 /=\=L-\ or 55 55

5. A compound according to claim 1 of the formula 10 GB2168704A 10 H 11 OH ' - Qm - W.1 ":tN 2 CE (CE CH N 3 2)7 2 N 0-, H 1. 0 p3 r - N, - N 5 S' (CH) 11, 1 5 i 2 IQ H 10 10 in which R3 is hydrogen or a protecting group and m is 1, 2 or 3; and salts thereof.

6. (1S,2R)-5- 3-[2-(2-1H-Tetrazol-5-yiethyithio)-1-hydroxypentadeca-3(E), 5(Z)-dienyl]pheny l -11-1tetrazole, or a pharmaceutically acceptable salt thereof.

7. A pharmaceutical formulation comprising a compound according to claim 2 or a pharma- 15 ceutically-acceptdble salt thereof in association with a pharmaceutically-acceptable diluent or 15 carrier therefor.

8. A process for producing a compound as defined in claim 1 which comprises reacting a compound of formula 20 N 'N 20 1- - 1, 0, 1 (11) R CH=CH CH-CH-C9N N R R3 25 25 in which R' is as defined in claim 1 and R3 is a protecting group, with a thiol of formula N --N 30 N N 30 R2 in which R2 is hydrogen or a protecting group, optionally followed by removal of an R2 or R3 protecting group.

9. A compound according to claim 2 or a pharmaceutically-acceptable salt thereof, for use as 35 a pharmaceutical.

10. A compound according to claim 1 substantially as described with reference to Example 1.

Printed in the United Kingdom for Her Majesty's Stationery Office. Dd 8818935, 1986, 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies may be obtained.