GB2238788A - Tetrahydropyridine compounds - Google Patents

Abstract

Compounds of general formula (I> <IMAGE> wherein R<1> represents a halogen atom; a hydroxy, amino or mono- or di-alkyl amino group; or an alkyl, cycloalkyl or phenyl group each of which may be optionally substituted by one or more halogen atoms, hydroxy, alkoxy, amino or mono- or di-alkylamino groups; R<2> represents a hydroxy group; R<3> represents an optionally substituted phenyl group; R<4> represents a hydrogen atom, a halogen atom, an optionally substituted C1-6 alkyl group or an optionally substituted phenyl group; R<5> represents a hydrogen atom or an optionally substituted C1-6 alkyl group; and salts thereof, are useful as antibiotics.

Description

Heterocyclic Compounds The present invention relates to novel heterocyclic compounds, processes for preparing them, pharmaceutical compositions containing them and their use as antibacterial agents. More particularly this invention concerns novel tetrahydronicotinic acid derivatives.

Dihydronicotinic acid derivatives have previously been disclosed as antibacterial agents.

Thus for example UK Patent No. 2130580B claims 4-oxo-1,4-dihydronicotinic acid derivatives of formula

wherein Ra is a hydrogen atom or a carboxyl protecting group, Rb Is a substituted aryl group (such as phenyl) or a substituted or unsubstituted heterocyclic group and Rc is inter alia a substituted or unsubstituted aryl group (such as phenyl). The specification lists a vast range of possible substituents which may be present on the groups Rb and Rc. The compounds are said to have broad-spectrum, antibacterial activity.

UK Patent No. 2130580B also discloses, as intermediates, tetrahydronicotinic ester derivatives of formula (B).

wherein Rb and Rc are defined as in formula (A) and Rd is a carboxyl protecting group.

Similarly UK Patent Application No. 2013190A discloses, as intermediates in the preparation of dihydronicotinic acid derivatives, compounds of formula (C).

where Re represents a hydrogen atom or a C1-6 alkyl group; represents a C1 8 alkyl, C3 10 cycloalkyl, -lo cycloalkyl C1 6 alkyl, C1-6 alkoxy or C16 alkoxy-C1-6alkyl group; and Rg represents inter alia an optionally substituted phenyl group.

Japanese Laid-Open Patent Application No. 246163/86 discloses compounds of formula (D)

where Rh is a carboxyl or protected carboxyl group; Ri and Rj are inter alia optionally substituted phenyl groups; Rk is hydrogen, halogen or a lower alkyl group; Z is N or CH and --- --is a single or double bond. In the majority of the exemplified compounds ~~~ - represents a double bond and in the few instances where " is a single bond and Z is CH then Rh is an esterified carboxyl group. The compounds are generally stated to possess anti-bacterial activity, but the single biological test result given is for a dihydronicotinic acid derivative.

We have now surprisingly discovered that certain tetrahydronicotinic acid derivatives possess advantageous antibacterial activity.

In a first aspect the present invention provides a compounds of general formula (I)

wherein R represents a halogen atom; a hydroxy, amino or mono- or di-alkyl amino group; or an alkyl, cycloalkyl or phenyl group each of which may be optionally substituted by one or more halogen atoms, hydroxy, alkoxy, amino or mono- or di-alkylamino groups; R represents a hydroxy group; R represents an optionally substituted phenyl group; R4 represents a hydrogen atom, a halogen atom, an optionally substituted C1 6 alkyl group or an optionally substituted phenyl group; R5 represents a hydrogen atom or an optionally substituted C16 alkyl group; and salts thereof.

In compounds of formula (I) an alkyl group or the alkyl moiety of an alkoxy or alkylamino group may be a straight or branched chain alkyl group having from 1 to 6 carbon atoms, and may be for example a methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, pentyl or hexyl group. Preferably an alkyl group contains 1 to 4 carbon atoms.

A halogen atom may be fluorine, chlorine, bromine or iodine.

R Preferably represents a halogen atom, such as a chlorine, bromine or fluorine atom; a C1 6 alkyl group, especially a C14 alkyl group, such as methyl or ethyl; or a halo 1-4 alkyl group, such as trifluoromethyl.

The group R2 may be attached to any one of the 4, 5 or 6 position of the phenyl ring, with respect to the tetrahydropyridine ring.

When one or both of R4 and R5 represents an optionally substituted alkyl group suitable substituents include halogen atoms and hydroxy, C1 4 alkoxy, amino, and C1 4 alkylamino groups. Preferably at least one of R and R5 represents hydrogen.

Substituents which may be present on the phenyl ring represented by any of R3, R4 and R5 include halogen atoms, hydroxy, alkoxy, alkyl, amino and mono- and di-alkylamino groups.

Compounds of formula (I) may form salts with bases. Compounds of formula (I) which contain basic groups, such as a basic amino group may also form salts with acids.

Suitable base salts include inorganic base salts such as alkali metal (e.g. sodium and potassium) salts and alkaline earth metal (e.g.

calcium) salts; organic base salts, e.g. phenylethylbenzylamine, dibenzylethylenediamine, ethanolamine and diethanolamine salts; and amino acids salts, e.g. lysine and arginine.

Suitable acid addition salts include those formed from hydrochloric, hydrobromic, nitric, perchloric, sulphuric, citric, tartaric, phosphoric, lactic, benzoic, glutamic, oxalic, aspartic, pyruvic, acetic, succinic, fumaric, maleic, oxaloacetic, isethionic, stearic, phthalic, methanesulphonic, p-toluene sulphonic, benzenesulphonic, lactobionic and glucuronic acids.

For use in medicine it will be appreciated that the salts should be pharmaceutically acceptable. However other salts may also find use eg. as intermediates in the preparation of compounds of formula (I), Compounds according to the present invention exhibit antibacterial activity in vitro, against both Gram-positive and Gram-negative organisms. In particular, compounds of formula (I) have been found to possess good activity against strains of Staohvlococcus aureus; Vibrio cholerae; Pasturella multocida; Salmonella organisms such as Salmonella typhimurium and Salmonella tvohosa; Shigella flexneri; strains of Escherichia coli; and Citrobacter freundii.

The compounds of formula (I) may be used in the treatment of a variety of bacterial diseases in human and/or veterinary medicine.

For administration to humans and animals it is preferable to present a compound of formula (I) as a pharmaeutical formualtion although the compounds alone may be administered if desired. Thus according to a further aspect of the invention there is - provided a pharmaceutical composition adapted for human or veterinary use comprising as active ingredient a compound of formula (I), together with at least one pharmaceutically acceptable carrier or excipient. Such compositions may be formulated in conventional manner, for administration by any convenient route, such as by oral, parenteral, topical or rectal administration.

Formualtions for oral administration include tablets; capsules; powders; liquid preparations such as aqueous or oily solutions, syrups, emulsions or suspensions. Tablets and capsules may include one or more pharmaceutically acceptable excipients such as binding agents e.g. polyvinylpyrrolidone; fillers e.g. lactose, sucrose, mannitol or microcrystalline cellulose; lubricants e.g. stearic acid, magnesium stearate, talc or silica; disintegrants e.g. potato starch; and wetting agents e.g. sodium lauryl sulphate.Liquid preparations for oral administration may contain for example pharmaceutically acceptable ingredients such as suspending agents e.g. glucose or sugar syrup or hydrogenated edible salts; emulsifying agents e.g. acacia; non-aqueous vehicles e.g. oily esters or fractionated vegetable oils; and preservatives e.g. methyl or propyl p-hydroxybenzoates; buffers; and flavouring, colouring and/or sweetening agents.

For parenteral administration the compounds may be presented in sterile aqueous or non-aqueous solutions or suspensions, which may contain antioxidants, buffers and other pharmaceutically acceptable additions as necessary.

Pharmaceutical compositions for topical administration according to the present invention may be formulated as an ointment, cream, suspension, lotion, powder, solution, paste, gel, spray, aerosol or oil. Altenatively, a formulation may comprise a dressing such as a bandage or adhesive plaster impregnated with active ingredients and optionally one or more excipients or diluents. Carriers which may be used include e.g. polyhydric alcohols such as polyethylene glycols, propylene glycol or glycerol. Suitable excipients are those known in the art to be appropriate.

For rectal administration the compounds may be formulated as suppositories, with conventional suppository bases such as cocoa butter or other glycerides.

Compounds of general formula (I) may be prepared by methods known in the art for preparing similar compounds. Thus, according to a first general process (A), compounds of formula (I) may be prepared from a compound of general formula (II):

(wherein R to R5 are as defined above for general formula (I) ånd R is a group convertible to -COOH) by reaction to convert the group R6 into a -COOH group.

The group R6 may be any group which can be converted into a carboxyl group -COOH. It will be appreciated that the group R6 should be convertible to -COOH under conditions which do not disrupt other groups present in the molecule. Groups R6 which may be employed thus include protected carboxyl groups -CO2R7, amides -CONH2, hydrazides -CONNH2 and nitriles -CN.

The carboxyl protecting group R7 may be any suitable carboxyl protecting group. A wide variety of such groups are known in the art, such as those disclosed in "Protective Groups in Organic Chemistry" McOmie (Plenum Press, 1973) and "Protective Groups in Organic Synthesis" Thedora W. Greene (Wiley-Interscience, 1981).

Thus the group R7 may be an ester group derived from an alcohol, phenol silanol or stannanol. As examples of such ester groups there may be mentioned alkyl groups, for example C16 alkyl groups such as methyl, ethyl and t-butyl groups; substituted alkyl groups such as alkoxy-, alkoxyalkoxy- and aralkoxy-alkyl (e.g. methoxymethyl, methoxyethoxymethyl and benzyloxymethyl), alkylthioalkyl (e.g.

methylthiomethyl, methylthioethyl and 2-(p-nitrophenylthioethyl), sulphonyl- and sulphenyl-alkyl (e.g. 2-(p-nitrophenylsulphenyl)ethyl and 2- (p-toluenesulphonyl)ethyl), haloalkyl (e.g. 2,2,-trichloroethyl) silylalkyl (e.g. 2-trimethylsilylethyl), heterocyclic alkyl groups (e.g. pyridylmethyl), alkyl groups substituted with a carbonyl function (e.g. phenacyl, p-bromophenacyl, -methylphenacyl, p-methoxyphenacyl and diacylmethyl) and N-phthalimidomethyl; cycloalkyl group such as cyclopentyl and cyclohexyl; alkenyl groups such as allyl and cinnamyl; phenyl and substituted phenyl groups such as p-methylthiophenyl; aralkyl groups, such as benzyl and benzyl substituted by for example halo (e.g. p-bromobenzyl), nitro (e.g.

p-nitrobenzyl), alkoxy (e.g. p-methoxybenzyl) or alkyl (e.g.

(2,4,6- trimethoxybenzyl), triphenylmethyl, diphenylmethyl, l-methyll-phenylethyl, bis(o-nitrophenyl)methyl and 9-anthrylmethyl; silyl esters such as trialkylsilyl (e.g. trimethylsilyl, triethylsilyl, t-butyldimethylsilyl and i-propyldimethylsilyl) and phenyldimethylsilyl; and stannyl esters for example alkylstannyl esters such as triethylstannyl and tri-n-butylstannyl.

Removal of the carboxyl protecting group R7 from a compound of general formula (II) may be carried out according to methods well known in the art. Thus the group R7 may be removed by example by acid or base catalysed hydrolysis, by reaction with Lewis acids e.g. trifluoroacetic acid, formic acid, or a mixture of hydrochloric acid and acetic aicd, or by reduction e.g. using zinc in acetic or formic acid, or hydrogen in the presence of a catalyst e.g. palladium on charcoal.

Groups R6 such as amides, hydrazines and nitriles may be converted into a carboxyl group by hydrolysis, using methods known in the art.

Compounds of formula (I) wherein both R4 and R5 are other than hydrogen may be prepared by a second general process (B) comprising alkylation of a corresponding compound of formula (I) wherein one or both R4 and R5 are hydrogen. The alkylation reaction may conveniently be carried out in the presence of a solvent, preferably an inert organic solvent such as an amide (e.g. N,N-dimethylformamide) or an ether (e.g. tetrhydrofuran). The alkylating agent may be a compound of formula R5 L (wherein L is a leaving atom or group, such as a halogen atom or a tosylate group) or a sulphate (R5)2SO4. Thus for example the alkylating agent may be an alkyl halide e.g. methyl iodide, an alkyl tosylate, e.g. methyl tosylate or a dialkylsulphate e.g. dimethylsulphate.The reaction will generally be effected in the presence of a base, such as an alkali metal carbonate e.g. sodium or potassium carbonate, an alkali metal alkoxide e.g. sodium or potassium ethoxide or t-butoxide, or an alkali metal hydride e.g. sodium hydride, or an acid scavenging agent e.g. propylene or ethylene oxide.

The reaction may conveniently be carried out at a temperature in the range -20 to 1000C.

Compounds of general formula (II) may be prepared by cyclising a compound of formula (III):

The cyclisation reaction may be effected by heating the compound (III) in the presence of absence of solvent. When a solvent is present it is conveniently an organic solvent, such as an inert polar aprotic solvent. Solvents which may be employed include amides e.g.

N,N-dimethylformamide or N,N-dimethylacetamide; a sulphoxide e.g.

dimethylsulphoxide; and hexamethylphosphoramide. The reaction may be effected at a temperature in the range 500 to 1500C, conveniently at the reflux temperature of the solvent used.

Compounds of formula (III) may be prepared in two stages from a compound of formula (IV):

by reacting the compound (IV) with an acetal derivative of N,N-dimethylformamide (e.g. N,N-dimethylformamido-dimethelacetal or N,N-dimethylformamido-diethylacetal) to give a compound of formula (V).

which may then be reacted with a compound of formula (VI)

The reaction may conveniently be effected in the presence of an inert organic solvent. Suitable solvents include aromatic hydrocarbons, e.g. benzene, toluene or xylene; cyclic and acyclic ethers e.g.

dioxan, tetrahydrofuran or diethylether; halogenated hydrocarbons e.g.

methylene chloride or chloroform; and amides e.g. N,N,-dimethylformamide or N,N-dimethylacetamide. The two stages of the reaction may if desired be effected in different solvents, but in general they may be conveniently be carried out using the same solvent. The reaction temperature may conveniently be in the range 0 to 1000C.

Compounds of formula (IV) may be prepared by methods well known in the art, for example by means of a Wittig reaction between an aldehyde R3CHO and a phosphonium compound of formula (VII)

Compounds (VII) may themselves be prepared from an appropriate ester of acetoactic acid, by reaction with trimethylorthoformate in the presence of an acid, such as sulphuric acid, followed by bromination and reaction which triphenylphosphine.

The invention will now be illustrated by the following non-limiting examples.

PreDaration 1 Ethvl 3-methoxv crotonate Ethylacetoacetate (156g, 1.20 mol) trimethyl orthoformate (129g, 1.215 mol) and sulphuric acid (15 drops) were mixed together and allowed to stand at room temperature (ca. 20 ) for 3 days. A slight excess of quinoline (ca. 20 drops) was then added and the mixture distilled to give the title compound as a colourless oil (147.16 g) b.pt 72-720 at 15 mm.

Preparation 2 Ethvl 4-bromo-3 -methoxvcrotonate A solution of the product of Preparation 1 (94.85 g, 0.658 mol), NBS (122.96 g, 1.05 eq.) and AIBN (30 mg) in carbon tetrachloride (11) was heated at reflux with a 200W incandescent lamp until complete consumption of the NBS was noted (ca. 2 hours). The mixture was allowed to cool to room temperature, diluted with petrol (60-80, 0.5 L) and filtered. The filtrate was washed with saturated sodium bicarbonate solution, dried (MgSO4) and evaporated in vacuo to a yellow oil which was purified by distillation to give the title compound (106.05 g) b.pt. 137-1400 at 15 mm.

Mass spec. M 222,224 Preparation 3 F3-(Ethoxvcarbonvl) allvl-2-methoxvl triDhenvlDhosDhonium bromide The product of Preparation 2 (80.68 g, 0.36 mol) and triphenylphos phine (94.9 g, 1 eq.) were dissolved in benzene (1L) and stirred at room temperature for 3 hours. The crystalline solid which formed was collected by filtration, the filtrate stirred for a further 16 hours at room temperature and a second crop of crystalline solid was filtered off. The combined solids were washed with diethyl ether and dried (450 in vacuo) to give the title compound (159.07 g) m.pt 85-88 .

Preparation 4 Ethvl 5-(4-dimethvlaminophenvl)-3-methoxv-2.4-pentadienoate The product of Preparation 3 (40 g, 82.4 mmol) and 4-dimethylaminobenzaldehyde (11.18 g, 0.91 eq.) in methanol (150 ml) were stirred at room temperature. To this solution was added a solution of sodium methoxide in methanol (28%, 15.9 g, 1 eq.) dropwise over 10 mins, with stirring. When addition of the sodium methoxide solution was complete the mixture was stirred for a further 20 mins at room temperature then evaporated in vacuo. Water (100 ml) was added to the residue and the mixture extracted with diethylether (2 x 50 ml). The combined extracts were dried (MgS04) and evaporated in vacuo to give a yellow oil. Diethyl ether was added to the oil and the solid which precipitated was removed by filtration.The filtrate was evaporated in vacuo to give an orange oil which was further purified by column chromatography (silica, dichloromethane) to give yellow oil (14.76 g) which was shown by tlc to contain the title compound as the major component Rf- 0.62 (CHC13): mass spec. M+ ca. 275.

This product was used directly in the next stage, without further purification.

Preparation 5 Ethvl 5-(4-dimethvlaminophenvl)-3-oxo-4-pentenoate The product of Preparation 4 (14.67 g; 0.053 mol) in dioxan (100 ml) was treated with O.lN sulphuric acid (87 ml) and heated at 1000C for 1.5 hours. The mixture was allowed to cool to room temperature, water (150 ml) was added and the resulting precipitate was filtered, washed with water and dried (suction followed by a vacuum oven at 500 for 3 hours) to give the title compound (11.4 g) m.pt 83-860 N.m.r. and i.r.

spectra are consistent with the structure indicated.

Preparation 6 Ethvl 5- (4-dimethvlaminovhenvl) -2- (4-hvdroxv- 2-methvlohenvl) - aminomethvlene- 3 -oxo-4-nentenoate The product of Preparation 5 (2.0 g, 7.65 mmol) in dry benzene (50 ml) and N,N-dimethylformamide dimethylacetal (1.19 g, 1.3 eq.) were stirred at 60 for 3.5 hours. The mixture was then evaporated in vacuo to a red oil which was taken up in benzene (50 ml). To this solution was added 2-methyl-4-hydroxyaniline (0.94 g, 1 eq.) and the mixture stirred at room temperature for 2 hours. The resulting precipitate was filtered, washed with toluene (10 ml) and diethyl ether (2 x 40 ml) and dried to give the title compound (2.05 g) m.pt 179-180 , n.m.r. and i.r. spectra consistent with structure.

Preparation 7 Ethvl 6-(4- dimethvlaminoDhenvl) -l-(rc-hvdroxv-2 -methvlhenvl)- 4-oxo-1 .4.5. 6-tetrahvdronicotinate The product of Preparation 6 (2.0 g, 5 mmol) in N,N-dimethylformamide (20 ml) was heated at reflux for 6 hours. The mixture was then evaporated in vacuo to an orange oil, which was kept under nitrogen at (freezer) for 7 days. The oil was then purified by flash chromatography (silica, 5% methanol/chloroform) to give the title compound (1.21 g) as a cracked glass. Mass spectrum M+ 394, n.m.r.

and i.r. spectra consistent with structure indicated.

Preparation 8 Ethvl 2-(2-chloro-4-hvdroxXphenyl)aminomethvlene-5-(4-dimethYlamino- Dhenvl)-3-oxo-4-pentenoate The product of Preparation 5 (1.0 g, 3.8 mmol) and N,N-dimethylformamide dimethyl acetal (0.68 g, 1.5 eq.) in dry benzene (30 ml) were heated and stirred at 60 for 3 hours, then evaporated in vacuo to a red oil, which was taken up in benzene (40 ml). To this oil was added 2-chloro-4-hydroxyaniline (0.55 g, 1 eq.) and the mixture stirred at room temperature for 3 hours. The resulting yellow precipitate was filtered, washed with benzene and diethyl ether, and dried to give the title compound (0.68 g) m.pt. 171 to 172 . Mass spec. M 414, Preparation 9 Ethvl 1-(2-chloro-4-hydroxvDhenel)-6-(4-dimethelaminophenYl)-4-oxo- 1.4.5. 6 - tetrahvdronicotinate The product of Preparation 8 (0.65 g, 1.57 mmol) in N,N-dimethylformamide (30 ml) outgassed with nitrogen, was heated at reflux for 7 hours under nitrogen. The mixture was then allowed to stand at room temperature overnight followed by heating at reflux for a further 5 hours. The resulting mixture was evaporated in vacuo to a black oil which was purified by flash chromatography (silica, 5% methanolchloroform) to give the title compound (0.42 g) as an orange/red cracked glass.

This product was used directly in the next stage.

PreDaration 10 3-(Ethoxyearbonsl)-6-phensl-2.4-dioxo-5-hexane Ethyl acetoacetate (40 g, 0.3 mol) was added slowly to a solution of sodium ethoxide (freshly prepared from 7.07 g in ethanol (100 ml)).

The mixture was stirred for 0.5 hour and evaporated in vacuo as near dryness as possible. Xylene (250 ml) was added and the solution evaporated to ca. 200 ml. Cinnamoyl chloride (51.2 g, 1 eq.) in xylene (dry, 100 ml) was added to the stirred suspension over 1 hour and the mixture stirred at room temperature overnight. The precipitate of sodium chloride which formed was filtered off and the filtrate evaporated in vacuo to a light yellow viscous oil which crystallised on cooling. The crystalline solid was filtered, washed with 40-60 petrol and dried (suction) to give the title compound (44.4 g) m.pt. 37-420 mass spectrum M+ 260. This material was used directly in the next stage, without further purification.

Preparation 11 Ethvl 5-phenyl-3-oxo-4-pentenoate The product of Preparation 10 (44.0 g, 0.169 mol) in sodium hydroxide (1N, 170 ml) was saturated with ammonia at 0 . The mixture was allowed to stand at room temperature for 1 hour, after which it was filtered and the filtrate acidified with 3N sulphuric acid. The solution was re-cooled to room temperature and an oily precipitate which formed was taken up in diethyl ether, dried (MgSO4) and evaporated in vacuo to a yellow oil. This oil was taken up in diethyl ether (20 ml) and 40-60 petrol (100 ml) added. The solution was kept at (freezer) for ca. 48 hours.The solid which formed was filtered, washed with 40-60 petrol and dried (suction) to give the title compound as a yellow crystalline solid (15.5 g). m.pt. 40-420 Mass spectrum M+ 218. This product was used directly in the next stage without further purification.

Preparation 12 Ethvl 2-dimethvlaminomethylene-5-phenvl-3-oxo-4-pentenoate The product of preparation 11 (8 g, 37 mmol) was dissolved in dry benzene (50 ml) and N,N-diemthylformamide dimethylacetal (5.6 g, 1.3 eq.) added. The solution was stirred at 600 for 2.5 hours, and then evaporated in vacuo to give a red oil (10 g) which was used directly in the next stage without further purification t.l.c. Rf - 0.30 (CHC13) Preparation 13 Ethvl 2-(4-hYdroxY-2-methYlphenYl)aminomethylene-5-shenyl-3-oxo-4 pentenoate The product of Preparation 12 (10 g, ca. 36 mmol) in dry benzene (30 ml) was stirred at room temperature, 2-methyl-4-hydroxyaniline (4.5 g, 1 eq) was added and the mixture stirred at room temperature for 2 hours.After standing overnight the yellow precipitate which formed was filtered, washed with benzene (5 ml) and dried to give the .title compound (10.02 g) m.pt. 171-1730. Mass spectrum M+ 351.

Preparation 14 Ethvl 1- (4-hvdroxv-2-methvThhenvl)-6-nhenvl-4-oxo-1.4.5 .6- tetrahvdronicotinate The product of Preparation 13 (8.0 g, 22.8 mmol) in N,N-dimethylformamide (50 ml) was heated at reflux for 3 hours, and then evaporated in vacuo to give the title compound as an orange/red oil (7.89 g) which was used without further purification.

t.l.c. Rf = 0.35 (MeOH/CHC13, 1:9) PreParation 15 D-Nitrobenzvl 4-methvl-3-oxo-5-Dhenvl-4-Dentenoate a-Methyl cinnamic acid (5.0g) was reacted with carbonyl diimidazole (5.5g, 1 equiv) and p-nitrobenzylmalonate magnesium salt (16.98g 1.1 equiv) in tetrahydrofuran. The mixture was stirred at room temperature in N,N-dimethylformamide for 18 hours to give a yellow oil, which was purified by flash chromatography to give the title compound (1.8g).

PreParation 16 D-Nitrobenzvl 2- (4-hvdroxv-2-methvlnhenvl) aminomethvlene-4-methvl-3- oxo-5-henvl-4-Dentenoate The product of Preparation 16 (1.8g) in dry benzene and N,N-dimethylformamide dimethylacetal were stirred at 60 0C for 3 hours then the mixture was evaporated to a green oil, dissolved in benzene (20ml) and 4-amino-3-methylphenol (0.65g, 1 equiv) was added. The mixture was stirred at room temperature overnight, then evaporated and subjected to column chromatography to give the title compound (2.26g) which was used in the next stage without purification.

Preparation 17 p-Nitrobenzyl 1- (4-hvdroxv-2-methylnhenvl) -5-methvl-4-oxo-6-henvl- 1.4.5.6-tetrahvdronicotinate The product of Preparation 16 (2.2g) in N,N-dimethylformamide (30ml) was heated at reflux for 8 hours then left at room temperature overnight. The resulting red oil was purified on silica gel to give an oil (1.3g) which was used in the next stage without further purification.

Example 1 6-(4-dimethvlaminophenvl)-1-(4-hvdroxv-2-methylphenYl)-4-oXo-1,4,5,6-- tetrahvdronicotinic acid The produce of Preparation 7 (1.0 g,2.53 mmol) in aqueous methanol (20 ml) was heated at reflux with 10ml of a 10% aqueous potassium hydroxide solution for 1 hour. The mixture was then evaporated in vacuo to ca. 15 ml, diluted with water (20 ml) and acidified to pH 5-6 with a minimum of acetic acid. The resulting orange precipitate was filtered, washed with water and dried. This solid was recrystallised from ethanol/toluene (1:19) to give the title compound (0.75 g) as a pale yellow crystalline solid.Further recrystallisation gave 0.55 g of product, associated with 0.45 mol.toluene. m.pt. 167-1740 (dec., softens at > 1540). n.m.r. and i.r. spectra consistent with structure indicated.

Example 2 6-(4-DimethvlaminoDhenyl)-1-(4-hvdroxv-2-chlorophenvl)-4-oXo-1.4.5.6-- tetrahvdronicotinic acid The product of Preparation 9 (0.42 g, 1.01 mmol) in 50% aqueous ethanol (30 ml) was treated with 10 ml of a 10% aqueous potassium hydroxide solution, and the mixture heated at reflux for 2 hours. The reaction mixture was then evaporated to ca. 20 ml, cooled to room temperature and acidified to pH 6. The resulting brown precipitate was filtered, washed with water and dried to give a solid which was recrystallised from methanol/chloroform to give the title compound (0.23 g) as an orange-brown cracked glass. m.pt. 135 to 1400 (dec, shrinks > 1250).

n.m.r. and ir. spectra consistent with structure indicated.

Example 3 1- (4-Hvdroxv-2-methvlhenv1) 4-oxo-6-nhenyl-l .4.5. 6-tetrahydronicotin- ic acid 0.2 hvdrate The product of Preparation 14 (3.89 g, 11 mmol) in aqueous methanol (50%, 30 ml) was treated with 30 ml of a 10% aqueous potassium hydroxide solution and heated at reflux for 2.5 hours. The reaction mixture was then evaporated to ca. 40 ml, diluted with water (40 ml) and acidified with sulphuric acid. The precipitate which formed was filtered, washed with water (x4), dried (suction) and then recrystallised from ethanol to give the title compound (3.21 g). This was further recrystallised to give a first crop of the title compound (2.74 g) and a second crop (0.04 g) (combined yield 2.78 g) mpt 168 to 1720 n.m.r. and i.r. spectra consistent with structure indicated.

Example 4 1-(4-Hvdroxv-2-methv1henvl-5-methvl-4-oxo-6-nhenvl-l.4.5.6- tetrahvdronicotinic acid The product of Preparation 17 (1.3g) in 30ml of a 1:1 methanol: water mixture was treated with 20ml of 10% aqueous potassium hydroxide and the mixture was refluxed for 1.5 hours, evaporated to ca.30m1, and acidified with concentrated sulphuric acid to give a yellow-brown precipitate which was washed with water dried and recrystallised to give the title compound (80mg) as a mixture of diastereoisomers m.p.

220-2210C: n.m.r. and i.r. spectra were consistent with the structure indicated.

The following compounds were prepared in a similar manner to the compound of Example 1, starting from the product of Preparation 5 and the appropriate aniline.

Compound No: 5 1- (2-bromo-4-hydroxyphenyl) -6- (4-dimethylaminophenyl) - 4-oxo-1,4,5,6-tetrahydronicotinic acid m.p. 128-134 C.

6 6-(4-dimethylaminophenyl)-1-(3-hydroxy-6-methylphenyl) 4-oxo-1,4,5,6-tetrahydronicotinic acid m.p. 131-1350C shrinks > 120 C. Product analyses for 0.24mol Et2O.

7 6- (4-dimethylaminophenyl) -1- (4-hydroxy-2-trifluorometh- ylphenyl)-4-oxo-l,4,5,6-tetrahydronicotinic acid m.p.

124-1280C shrinks > 1160. Analysis indicated the product to contain 0.07mol CHIC13 8 6- (4-Dimethylaminophenyl) -1- (2-fluoro-4-hydroxyphenyl) - 4-oxo-1,4,5,6-tetrahydronicotinic acid mp 117-1230C shrinks > 1070C. Product contains 0.11mol CHIC13 by analysis.

9 6-(4-dimethylaminophenyl)-1-(2-ethyl-4-hydroxyphenyl) 4-oxo-1,4,5,6-tetrahydronicotinic acid mp 119-1230C shrinks > 1100C. Analysis indicates product to contain 0.09mol CHC13 The following compound was prepared in an analogous manner to the compound of Example 3, starting from the product of preparation 11 and the appropriate aniline; 10 l-(2-Chloro-4-hydroxyphenyl)-4-oxo-6-phenyl-l,4,5,6- tetrahydronicotinic acid mp 106-1150C shrinks 950C.

Anaylsis indicates product to contain O.lmol CHCL3 Compounds 5-10 gave n.m.r. and i.r. spectra consistent with the structure indicated.

Biological Test Results Minimum Inhibitory Concentration ( g/ml) Compound of Example No.

Organism 1 2 3 Staph.aureus CN491 0.3 0.1 1.0 Staph.aureus P424 0.3 0.1 1.0 Vibrio cholerae ATCC14035 0.1 1.0 0.1 Past.multocida ATCC6587 0.1 1.0 0.1 Sal. typhimurium S8587 0.3 0.3 3.0 Sal. typhosa 3.0 1.0 10.0 Shig. flexneri CN6007 1.0 1.0 3.0 E. coli CN314 3.0 0.3 3.0 E. coli P855 1.0 0.3 3.0 Citro.Freundii P1436 1.0 1.0 3.0 Formulation Examples A) 2% Cream % w/w Compound of formula (I) 2.0 Fractionated Coconut oil 11.0 (Miglyol 812) Dynaston 114 8.0 Tween 60 2.3 Tween 80 1.2 Propylene glycol 10.0 Phenylethyl alcohol 1.0 Purified Water to 100.0 B) 1% Gel % w/w Compound of formula (I) 1.00 Poloxamer 407 25.00 Ethanol 20.00 Methyl paraben 0.15 Propyl paraben 0.05 Purified water to 100.00 C) 1% Ointment % w/w Compound of formula (I) 1.00 Plastobase 50W to 100.00 D) Tablet Compound of formula (I) 500.0 mg Corn Starch 70.0 mg Lactose 83.8 mg Magnesium Stearate 4.2 mg Polyvinylpyrrolidone 14.0 mg Stearic Acid 28.0 mg The Compound of formula (I) is finely ground and intimately mixed with the powdered excipients, corn starch and lactose.The powders are wetted with a solution of polyvinylpyrrolidone dissolved in purified water and denatured alcohol to form granules. The granules are dried and mixed with the powdered stearic acid and magnesium stearate. The formulation is then compressed into tablets weighing approximately 700 mg each.

E) Capsules Compound of formula (I) 500.0 mg Corn Starch 50.0 mg Magnesium Stearate 3.0 mg The finely divided compound of formula (I) is mixed with powdered corn starch and wetted with denatured alcohol to densify the powder. The dried powder is mixed with stearic acid and filled into hard-shell gelatin capsules.

F) Syrup Compound of formula (I) 250.0 mg Dispersible cellulose 100.0 mg Glycerin 750.0 mg Sucrose 3,500.0 mg Flavouring Agent q.s.

Colouring Agent q.s.

Preserving Agent 0.1% Purified Water q.s. to 5.0 ml Dissolve the Sucrose in a portion of the Purified Water. Dissolve the preservative in a separate portion of Purified Water and add to the solution of Sucrose. Add the Glycerin, Flavouring Agent, Colouring Agent and Dispersible Cellulose and mix well. Add the drug suspended in a further portion of Purified Water and mix well. Make up to final volume with Purified Water and Mix.

G) IV Iniection Compound of formula (I) 5.0 mg Glycerin q.s. for isotonicity Preservative 0.1% Hydrochloric Acid or as needed for pH adjustment Sodium Hydroxide as needed Water for Injection q.s. to 10 ml The compound of formula (I) and preservative are added to the glycerin and a portion of the Water for Injection. Sodium hydroxide is added to dissolve the compound, followed by addition of glycerin. The pH is adjusted with hydrochloric acid or sodium hydroxide. ' Water for Injection is added to final volume. After mixing, the solution is sterilised by filtration through a 0.22 micrometer membrane filter and aseptically filled into sterile 10 ml ampoules or vials.

Claims (8)

Claims

1. A compound of general formula (I)

wherein R represents a halogen atom; a hydroxy, amino or mono- or di-alkyl amino group; or an alkyl, cycloalkyl or phenyl group each of which may be optionally substituted by one or more halogen atoms, hydroxy, alkoxy, amino or mono- or di-alkylamino groups; R represents a hydroxy group; R represents an optionally substituted phenyl group; R4 represents a hydrogen atom, a halogen atom, an optionally substituted C16 alkyl group or an optionally substituted phenyl group; R5 represents a hydrogen atom or an optionally substituted C16 alkyl group; or a salt thereof.

2. A compound according to claim 1 wherein R represents a halogen atom, a C16 alkyl group or a halo C1.4 alkyl group, or a salt thereof.

3. A compound according to either claim 1 or claim 2 wherein the group R2 is attached at the 4, 5 or 6 position of the phenyl ring, or a salt thereof.

4. A compound according to any of claims 1 to 3 wherein R is phenyl optionally substituted by a halogen atom, or a hydroxy, alkoxy, alkyl, monoalkylamino or dialkylamino group, or a salt thereof.

5. A compound according to any of claims 1 to 4 wherein at least one of R and R5 represents hydrogen or a salt thereof.

R1

6. A compound according to claim 1 wherein R represents a halogen atom, a C14 alkyl group, or trifluoromethyl; R2 represents a hydroxy group at the 4- or 5- position of the phenyl ring; R3 represents a phenyl group optionally substituted by a di-Cl 4 alkyl group; R4 represents a hydrogen atom or a C 1-4 alkyl group and R5 represents a hydrogen atom; or a salt thereof.

7. A pharmaceutical composition comprising a compound of formula (I) as defined in any of claims 1 to 6, or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable carrier therefor.

8. A process for preparing a compound of formula (I) or a salt thereof, which comprises (A) reacting a compound of formula (II)

(wherein R to R5 are as defined in any of claims 1 to 6 and R6 is a group convertible to -COOH) to convert the group R6 into the group -COOH; or (B) to prepare a compound of formula (I) wherein R and R each represents an alkyl group, alkylation of a compound of formula (I) wherein at least one of R4 and R5 is hydrogen; followed where necessary and/or desired by salt formation.