GB2131431A

GB2131431A - Benzofuran derivatives

Info

Publication number: GB2131431A
Application number: GB08332269A
Authority: GB
Inventors: Stephen Richard Baker; William Boffey Jamieson; Terry Donald Lindstrom; William James Ross
Original assignee: Lilly Industries Ltd
Current assignee: Lilly Industries Ltd
Priority date: 1982-12-04
Filing date: 1983-12-02
Publication date: 1984-06-20
Also published as: DK556483A; IE832830L; HUT36107A; IL70346A0; CA1212678A; GB2131431B; GB8332269D0; DK556483D0; EP0113534A1; KR840006984A; IE56364B1; GR81257B

Description

1

GB 2 131 431 A 1

SPECIFICATION

Novel pharmaceutical compounds and their preparation

This invention relates to novel compounds, to a process for their production and to their use as pharmaceuticals.

5 British Patent 2 030 142 discloses some aurone compounds having pharmaceutical properties and of the formula

^x-'\ /—v1

\ /V

where R and R1 take various substituent values. We have now discovered a group of related compounds which also possess useful pharmacological activity and that can be derived from them. 10 The compounds of the invention have the formula 10

(I)

in which R\ R2, R3, R4, R5 and R6 are the same or different and are hydrogen, halogen, C1_4alkyl,

C1_4alkoxy, C3_8cycloalkyl, optionally substituted phenyl, C1_4haloalkyl, C^acylamino, C.,_4alkylaminocarbonyl, amino, cyano, hydroxy, nitro, C3_4alkenyl, C3_4alkenyloxy, carboxy C,_2alkoxy, 15 carboxyl, tetrazol-5-yl or carboxyvinyl or in which R1 and R2 taken together at adjacent carbon atoms 15 represent a phenyl ring; or a salt or ester thereof.

A preferred group of compounds of the invention have the formula

"4 I! >

"3X / v

• 1

(I)

in which R\ R2 and R3 are the same or different and are hydrogen, halogen, C1_4alkyl, C,_4alkoxy, 20 C3_8cycloalkyl, optionally substituted phenyl, C.,_4haloalkyl, C^acylamino, C^alkylaminocarbonyl, 20 amino, cyano, hydroxy, nitro, C3_4alkenyl, tetrazol-5-yl or carboxyvinyl or in which R1 and R2 taken together at adjacent carbon atoms represent a phenyl ring, at least one of R1, R2 and R3 being other than hydrogen, and in which R4, R5, R6 are each hydrogen, halogen, C,_4alkyl, C^alkoxy,

C3_8cycloalkyl, optionally substituted phenyl, C^haloalkyl, C.,_4acylamino, C^alkylaminocarbonyl, 25 amino, cyano, hydroxy, nitro, C3_4alkenyl, carboxyl, tetrazol-5-yl or carboxyvinyl, provided that at least 25 one of R4, Rs and R6 is carboxyl or at least one of R1, R2, R3, R4, Rs and R6 is tetrazol-5-yl or carboxyvinyl; or a salt or ester thereof.

2

GB 2 131 431 A 2

A further preferred group of compounds of the invention have the formula

4 R.

X'\ A

-4- iix fi /2 , (ID

YY

X 1 X c

R->

3 ' .4 "

r°

in which either R1 and R2 are both hydrogen or R1 is carboxyl and R2 is hydrogen, C3_4alkenyl or C1_4alkyl, and R4, R5 and R6 are each hydrogen, nitro, hydroxyl, carboxyl, carboxy-C.,_2alkoxy, 5 C3_4alkenyl, C-,_4alkyl, C3_4alkenyloxy, C,_4alkoxy or the group where R7 and R8 are each hydrogen or C1_4alkyl; and salts and esters thereof.

The term "halogen" means especially chlorine, bromine and fluorine. The term "C1_4aikyi"

includes, for example, methyl, ethyl, propyl, isopropyl, butyl, tert butyl, being preferably methyl, ethyl or 10 tert-butyl. The term "C1_4alkoxy" includes, for example, methoxy, ethoxy, propoxy and butoxy, and is 10 preferably methoxy. The term "C3_8cycloalkyl" includes, for example, cyclopropyl, cyclopentyl and cycloheptyl, and is preferably cyclohexyl. The term "optionally substituted phenyl" includes, for example, phenyl optionally substituted with 1 to 3 substituents selected from methyl, methoxy,

halogen and nitro. The term "C^haloalkyl" can be, for example, any of the groups listed for "C1_4alkyl" 15 substituted with one to three halo atoms such as fluorine or chlorine, and is especially trifluoromethyl. 1 5 The term "C3_4alkenyl" is preferably allyl. The term "C.,_4acylamino" includes, for example, acetamido and groups of the formula RCONH— where R has the value of C1_3alkyl, and C^alkylaminocarbonyl includes, for example, N-isopropylcarboxamido, and groups of the formula

0

II

r2nc—

20 where R is hydrogen or C.,_4alkyl. "Amino" includes, for example, —NH2, mono C^alkylamino and di 20 C^alkylamino, especially dimethylamino and for example can be of the form

R7

/

—N

\

R8

where R7 and R8 are each hydrogen or Cn_4aIkyl. The term carboxy-C.,_2 alkoxy covers carboxymethoxy, 2-carboxyethoxy and 1 -carboxyethoxy. The preferred substituents for R1, R2, R3, R4, R5 and R6 are 25 hydrogen, halogen, C^alkyl, C.,_4alkoxy, cyclohexyl, trifluoromethyl, dimethylamino, hydroxy, carboxyl, 25 tetrazol-5-yl or carboxyvinyl.

A preferred group of compounds of formula (I) is one in which R1, R2 and R3 are selected from hydrogen, halogen, C1_4alkyl, Ct_4alkoxy, cyclohexyl, trifluoromethyl, dimethylamino, hydroxy, tetrazol-5-yl or carboxyvinyl at least one of R1, R2 and R3 being other than hydrogen, in which R4 is carboxyl and 30 in which R5 and R6 are selected from hydrogen, halogen, C^alkyl, C-^alkoxy, cyclohexyl, 30

trifluoromethyl, dimethylamino, hydroxy, carboxyl, tetrazol-5-yl or carboxyvinyl.

It is further preferred that R1 be selected from C^alkoxy, C1_4alkyl and halogen and R2 and R3 are both hydrogen. Similarly R4 is preferably chosen from carboxyl, tetrazol-5-yl or carboxyvinyl, and R5 and R6 are both hydrogen, and an especially preferred group of compounds are those having the following 35 formula 35

3

GB 2 131 431 A 3

/V 8

/ V\

*'-4- II /—\

\/v /~v

\ /'

• - •

in which R1 is C^alkoxy, C1_4alkyi or halogen and R4 is carboxyl, tetrazol-5-yl or carboxyvinyl, or a salt or ester thereof.

A further preferred group of compounds is one of formula (II) above, in which R1 is carboxyl 5 (especially in the 5-position), R2 (especially in the 7-position) is hydrogen, C3_4alkenyl or C,_4alkyl, and 5 R4, Rs and R6 are each hydrogen, hydroxyl, C3_4alkenyl, C1_4alkyl, C3_4alkenyloxy, C^alkoxy or the group when R7 and R8 are each hydrogen or C.,_4alkyl and of those compounds the most preferred are those 10 in which R1 is carboxyl (especially those substituted in the 5-position), R2 is hydrogen and R4, R5 and R6 10 are each hydrogen, carboxyl, C,_4alkyl or C,_4alkoxy.

Suitable salts of compounds of invention include for example, those of mineral bases such as alkali metal hydroxides, especially the potassium or sodium salts, or alkaline earth metal hydroxides, especially the calcium salts, or of organic bases such as amines for example trimethylamine. When the 15 compounds contain an amino group or a basic nitrogen atom, acid addition salts are included such as 15 those with inorganic acids, for example hydrochloric, hydrobromic, nitric, sulphuric or phosphoric acids, or with organic acids, such as organic carboxylic acids, for example, glycollic, maleic, hydroxymaleic,

fumaric, malic, tartaric, citric, salicylic, o-acetoxybenzoic, nicotinic or isonicotinic acid, or organic sulphonic acids for example methane sulphonic, ethane sulphonic, 2-hydroxyethane sulphonic, 20 toluene-p-sulphonic or naphthalene-2-sulphonic acid. Preferred esters are those derived from 20

C,_4alkanols, for example the methyl, ethyl, propyl, isopropyl and n-butyl. Also included are esters having a substituted alkyl group in view of the fact that it is often desirable to attach an ester group that cleave to give the free acid, and examples of such substituted alkyls include acetoxymethyl, methylthiomethyl, methoxyethyl, ethoxyethyl, methylsulphinylmethyl and methylsulphonylmethyl. 25 The preferred salts and esters are those which are pharmaceutically-acceptable but other 25

derivatives are also included in the invention since they may be useful as intermediates in the preparation, purification or characterisation of the pharmaceutical end product.

The invention includes a method of preparing compounds of the invention which comprises reducing a compound of formula

Vv!

30

\

■X/v'

-CH-

\ X

(III)

30

R6

The reduction is preferably carried out by the use of hydrogen and a metal catalyst, the latter preferably being a precious metal such as platinum or palladium. It has been found that 10 per cent palladium on charcoal is a convenient catalyst for this purpose. Generally the reduction process is carried out in a solvent, for example, acetic acid, and at a temperature from 0°C to 100°C, for example 35 at room temperature.

As mentioned above, the compounds of formula (III) are known and their method of preparation is described, for example, in British Patents 2 030 142,2 014 566 and 2 001 631. They may best be prepared by condensing an appropriately substituted benzaldehyde with a benzofuranone as depicted below:

4

GB 2 131 431 A 4

R1 B S4

^ V\ y-Hv"5

S'-T I /• ♦ «C-/ y-

;x/v , •=*x»s

R I

compound of formula (111)

It will be appreciated that many of the compounds of the invention can be converted one to another by introduction or conversion of groups in the benzofuranone or phenyl ring either during one 5 of the intermediate stages in the preparative reactions or in an end product. Thus, for example, a tetrazol-5-yl compound can be prepared from the corresponding cyano compound by reaction with an azide. When a nitro substituent is desired in the benzofuranone or phenyl nuclei, the corresponding unsubstituted compound can be nitrated with a mixture of concentrated nitric and sulphuric acids by the conventional method. The nitro compound can subsequently be converted to other substituents 10 such as amino or acylamino. The amino compound may be diazotised and the resultant diazonium salt converted to a variety of other products, for example, by decomposition in an alcohol to yield the corresponding alkoxy substituted compound or by reaction with a cuprous halide to yield the corresponding halo substituted compound. Hydroxy substituted compounds can be prepared from the corresponding methoxy compounds by cleavage with, for example, boron tribromide.

15 It will be appreciated that the compounds of the invention have an asymmetric centre at the carbon atom of the benzofuranone moiety linked to the benzyl group (carbon number 2) and this asymmetry gives rise to the existence of optical isomers. Substantially pure optical isomer can be prepared by chemical reaction in the presence of a chiral catalyst. Alternatively, a racemic mixture of both isomers can be separated by conventional chemical methods such as for example by the 20 preparation of diastereoisomers as salts with an optically-active base and subsequent liberation of the enantiomers.

The anti-allergy activity of the compounds of the invention and their pharmaceutically acceptable salts and esters has been demonstrated in guinea pigs using either the "guinea-pig chopped lung test" described by Mongar and Schild in the Journal of Physiology (London) 131, 107 (1956) or 25 Brocklehurst in the Journal of Physiology (London) 757, 416 (1960), or the "Herxheimer" test described in the Journal of Physiology (London) 117,251 (1952). In the "Herxheimer" test, which is based on an allergic bronchospasm induced in guinea pigs closely resembling an asthmatic attack in man, compounds exhibited activity at dosages ranging from 25 mg/kg to 200 mg/kg.

The compounds of the invention have also shown activity in tests devised to indicate anti-30 inflammatory activity as, for example, the adjuvant arthritis test (B. B. Newbould Chemotherapy of Arthritis Induced in Rats by Mycobacterial Adjuvant. Br. J. Pharmacol. 27, 127—136 (1963)).

The compounds of this invention are accordingly indicated for therapeutic use in the treatment of immediate sensitivity reactions and in particular in the treatment of asthma, as well as being of use in the treatment of anti-inflammatory diseases.

35 The compounds of this invention may be administered by various routes, for example, by the oral or rectal route, by inhalation, topically or parenterally, for example by injection, being usually employed in the form of a pharmaceutical composition. Thus the invention includes a method of administering a compound according to formula I to a mammal suffering from an allergic reaction or an inflammatory disease or to prevent such allergic or inflammatory disease. Pharmaceutical compositions also form 40 part of the present invention and are prepared in a manner well known in the pharmaceutical art and normally comprise at least one active compound in association with a pharmaceutically acceptable diluent or carrier. 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 example, be in the form of a capsule, sachet, paper or other container. Where the carrier serves as a diluent, it 45 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, elixires, 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 capsules, suppositories, injection solutions and suspensions and sterile packaged powders. For administration by inhalation, particular forms of 50 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 cellulose, methyl- and propyl-hydroxybenzoate, talc, magnesium stearate and mineral oil. The compositions of the invention may, as is well known in the art, be formulated so as to provide quick, sustained or delayed release of 55 the active ingredient after administration to the patient.

Where the compositions are formulated in unit dosage form, it is preferred that each unit dosage

5

10

15

20

25

30

35

40

45

50

55

5

GB 2 131 431 A 5

form contains from 5 mg to 500 g, more usually 25 to 200 mg, of the active ingredient. The term "unit dosage form" refers to physically discrete units suitable as unit dosages for human 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.

5 The active compounds are effective over a wide dosage range and, for example, dosages per day 5 will normally fall within the range of from 0.5 to 300 mg/kg, more usually in the range of from 5 to 100 mg/kg. However, it will be understood that the amount administered will be 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 10 ranges are not intended to limit the scope of the invention in any way. 10

The following Examples illustrates the invention.

Examples 1 to 3

3-[(2,3-Dihydro-5-methoxy-3-oxo-2-benzofuranyl}methyl]benzoic acid

(Z)-3-[(5-Methoxy-3-oxo-2-(3H)-benzofuranylidene)methyl]benzoic acid (10 g) was suspended in 15 glacial acetic acid (250 ml) and hydrogenated at room temperature and 60 p.s.i. pressure in the 15

presence of 10% palladium on charcoal (500 mg) for 1 hour. The catalyst was filtered off and the nearly colourless filtrate evaporated in vacuo to give a viscous oil which readily crystallised. This crystalline solid was slurried with a little diethyl ether and refiltered to give the title compound as an off-white crystalline solid, m.p. 143—152°C (with decomposition).

20 The following compounds were prepared in a similar manner: 20

4-[(2,3-Dihydro-5-methoxy-3-oxo-2-benzofuranyl)methyl]benzoic acid, m.p. 168°C (with decomposition).

4-[(2,3-Dihydro-6-methyl-3-oxo-2-benzofuranyl)methyl]benzoic acid, m.p. 188—190°C (with decomposition).

25 Example 4 25

(a) Z-3-[(2,3-Dihydro-5-methoxycarbonyl-3-oxo-2-benzofuranyl)methylene]benzoic acid

5-Methoxycarbonylbenzofuran-3-(2H)one (4.9 g) was dissolved in warm dioxan (50 ml). 3-Carboxybenzaldehyde (4.5 g) was then added followed by concentrated hydrochloric acid (10 ml). The mixture was heated on a steam bath for 15 minutes with formation of yellow crystals. After cooling 30 and addition of an equal volume of water, the crystalline product was filtered off and recrystallised from 30 dimethylformamide to give the title compound, m.p. 280°C.

(b) 3-[(2,3-Dihydro-5-methoxycarbonyl-3-oxo-2-benzofuranyl)methyl]benzoic acid

The product from (a) (1 g) was suspended in glacial acetic acid (100 ml) and hydrogenated at 60 p.s.i. in the presence of 10% palladium on carbon (100 mg). After 1 hour the catalyst was filtered off 35 and the colourless filtrate evaporated in vacuo to give a light straw coloured oil which crystallised on 35 standing. Recrystallisation from ethyl acetate/petrol gave the required product as off-white crystals, m.p. 140—143°C.

Claims

1. A compound of the formula

40 K V (I) 40

in which R1, R2, R3, R4, R5 and R6 are the same or different and are hydrogen, halogen, C1_4alkyl,

C1_4alkoxy, C3_8cycloalkyl, optionally substituted phenyl, C1_4haloalkyl, C^acylamino, C^alkylaminocarbonyl, amino, cyano, hydroxy, nitro, C3^4alkenyl, C3_4alkenyloxy, carboxy C^alkoxy, carboxyl, tetrazol-5-yl or carboxyvinyl, or R1 and R2 taken together at adjacent carbon atoms represent 45 a phenyl ring; or a salt or ester thereof. 45

2. A compound according to claim 1 in which R1, R2 and R3 are the same or different and are hydrogen, halogen, C1_4alkyl, C^alkoxy, C3_8cycloalkyl, optionally substituted phenyl, C^haloalkyl, Ci_4acylamino, C^alkylaminocarbonyl, amino, cyano, hydroxy, nitro, C3_4alkenyl, tetrazol-5-yl or carboxyvinyl or in which R1 and R2 taken together at adjacent carbon atoms represent a phenyl ring, at

6

GB 2 131 431 A 6

least one of R1, R2 and R3 being other than hydrogen, and in which R4, RB, R6 are each hydrogen,

halogen, C1_4alkyl, C1_4alkoxy, C3_8cycloalkyl, optionally substituted phenyl, C.,_4haloalkyl,

C^acylamino, C.,_4alkylaminocarbonyl, amino, cyano, hydroxy, nitro, C3_4alkenyl, carboxyl, tetrazol-5-yl or carboxyvinyl, provided that at least one of R4, R5 and R8 is carboxyl or at least one of R\ R2, R3, R4, 5 R5 and R6 is tetrazol-5-yl or carboxyvinyl; or a salt or ester thereof. 5

3. A compound according to claim 2 in which R1, R2 and R3 are selected from hydrogen, halogen, C1_4alkyl, C1^4alkoxy, cyclohexyl, trifluoromethyl, dimethylamino, hydroxy, tetrazol-5-yl or carboxyvinyl at least one of R1, R2 and R3 being other than hydrogen, in which R4 is carboxyl and in which R5 and R6 are selected from hydrogen, halogen, C1_4alkyl, C,_4alkoxy, cyclohexyl, trifluoromethyl, dimethylamino,

10 hydroxy, carboxyl, tetrazol-5-yl or carboxyvinyl. 10

4. A compound according to claim 2 in which R1 is C^alkoxy, C1_4alkyl or halogen and R2 and R3 are both hydrogen, R4 is carboxyl, tetrazol-5-yl or carboxyvinyl, and R5 and R6 are both hydrogen.

5. A compound according to claim 1 of the formula (II)

B V\ A

« x

6\/V"

\4=>v

3r\A

r6

15 in which either R1 and R2 are both hydrogen or R1 is carboxyl and R2 is hydrogen, C3_4alkenyl or 15

C1_4alkyl, and R4, R5 and R6 are each hydrogen, nitro, hydroxyl, carboxyl, carboxy-C1_2alkoxy,

C3_4alkenyl, C^alkyl, C3_4alkenyloxy, C^alkoxy or the group

R7

/

—N

\

R8

where R7 and R8 are each hydrogen or C1_4alkyl; and salts and esters thereof.

20 6. A compound according to claim 5 in which R1 is carboxyl R2 is hydrogen, C3_4alkenyl or 20

C1_4alkyl, and R3, R4 and Rs are each hydrogen, hydroxyl, C3_4alkenyl, C^alkyl, C3_4alkenyloxy,

C^alkoxy or the group

R6

/

—N

\

R7

when R6 and R7 are each hydrogen or C^alkyl.

25

7. A pharmaceutical formulation comprising a compound according to claim 1 or a 25

pharmaceutically acceptable salt thereof, admixed with a diluent or carrier therefor.

8. A process for producing a compound according to claim 1 which comprises reducing a compound of formula

R1

R2-

I I

\_x,.

30 in which R1, R2, R3, R4, R5 and R6 have the values defined in claim 1. 30

9. A compound according to claim 1 or a pharmaceutically-acceptable salt thereof, for use as a pharmaceutical.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1984. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.