[0001] The present invention relates to imidazole derivatives and salts thereof, to their
synthesis and intermediates therefor, to pharmaceutical formulations containing such
compounds and to the use of these compounds in medicine.
[0002] Thromboxane A
2 (TXA
2), a potent stimulator of blood platelet aggregation, is produced, in platelets, from
the prostaglandin endoperoxides PGG
2 and PGH
Z. Prostacyclin (PGI
Z), which has potent anti-aggregatory activity, is also produced (in blood vessel walls)
from PGG
2 and PGH
2 and it has been suggested that a balance between the production of TXA
2 and PGI
2 is the controlling factor in thrombus formation. It would, in consequence, be desirable
in the treatment and prophylaxis of thrombo-embolic disorders to be able to selectively
inhibit TXA
2 synthetase, thereby favouring the production of the anti-aggregatory agent PGI
Z.
[0003] Imidazole and 1-methylimidazole are known to provide some degree of inhibition of
the enzymic conversion of the endoperoxides (PGG
2 and PGH
2) to thromboxane A
2 by platelet microsomes (Moncada et al., Prostaglandins, 13/4, 611-618, 1977). Certain
1-n-alkylimidazoles, especially 1-n-dodecylimidazole and its higher homologues have
been described as being capable of lowering serum cholesterol levels (U.K. Patent
No. 1 364 312; Biochem. Pharmacol. 24, 1902-1903, 1975).
[0004] We have now discovered that TXA
2 synthetase may be inhibited by 1-alkylimidazoles of formula (I) and acid addition
salts thereof. The compounds of formula (I) and their salts are hereinafter referred
to as the "active compounds".
[0005] The compounds of formula (I) are novel and of formula:
in which A is a straight or branched, saturated or unsaturated acyclic hydrocarbon
radical of from 1 to 3 carbon atoms and R is a cycloalkyl or cycloalkenyl radical
of from 4 to 9, preferably from 5 to 8 carbon atoms and optionally substituted by
one, two, three or more alkyl radicals each containing from 1 to 4 carbon atoms with
the proviso that when A is a methylene radical R is not unsubstituted cyclohexyl.
[0006] In formula (I) examples of cycloalkyl radicals are cyclobutyl, cyclopentyl, cyclohexyl,
cycloheptyl, arid cyclooctyl; cycloalkenyl radicals include cyclohex-3-enyl, cyclopentenyl,
1,4-cyclo- hexadienyl and cyclohept-2-enyl.
[0007] A valuable class of compounds of formula (I) are those in which R is cyclohexyl,
cycloheptyl, cyclooctyl or cycloalkenyl of 6 to 8 carbon atoms and A is -CH
2- or -(CH
2)
2-. Compounds of formula (I) may also be used as acid addition salts thereof, especially
as pharmaceutically acceptable ones.
[0008] Especially preferred compounds include:
1-Cyclooctylmethylimidazole
1-Cyclohex-3-enylmethylimidazole
1-Cyclohexylethylimidazole
1-Cycloheptylmethylimidazole
and acid addition salts thereof.
[0009] Other preferred compounds include:-
1-Cyclopentylmethylimidazole
1-(4-Methylcyclohexylmethyl)imidazole
1-Cyclobutylmethylimidazole
I-Cyclooctylvinylimidazole
1-(1-Cyclooctylethyl)imidazole
1-(2-Cyclooctylethyl)imidazole
1-(3-Cyclooctylpropyiiinidazole
1-(Cyclohept-2-enylmethyl)imidazole
1-Cyclononylmethylimidazole
and acid addition salts thereof.
[0010] In contrast to imidazole and 1-methylimidazole the compounds of formula (I) are more
potent inhibitors of TXA
Z synthetase. Many of the compounds (for example in (I) R is cycloalkyl or cycloalkenyl,
n is 1, and A is -CH
Z- or -(CH
2)
2- are also more selective in their action in not inhibiting other prostaglandin-generating
enzymes such as cyclo-oxygenase. The compounds of formula (I) also do not produce
the side-effects found with imidazole upon in vivo administration. The compounds of
formula (I) are further capable of inhibiting platelet aggregation in vivo and also
are capable of disaggregating platelet clumps. The compounds 1-cyclooctylmethylimidazole,
1-cyclohex-3-enylmethyl- imidazoleand 1-cyclohexylethylimidazole and their salts especially
displaying these properties.
[0011] Imidazoles of formula (I) and acid addition salts thereof may be made by any method
known in the art for the synthesis of compounds of analogous structure. In general
these methods comprise linking the imidazole ring to the remainder of the molecule;
converting a precursor molecule by elimination of a functional group from the imidazole
ring; and formation of the desired compound from a corresponding imidazoline, pyrazole
or unsaturated analogue.
[0012] A most convenient method of synthesis involves the reaction of imidazole (formula
II) or a salt thereof with an alkylating agent of formula (III) :
wherein R and A are as defined in formula (I) and Z is a leaving group. This reaction
is well established in the literature, and the leaving group may be chosen from a
variety of substituents but especially halo, preferably chloro or bromo, or from p-toluenesulphonyloxy
but other arylsul- phonyloxy, alkanesulphonyloxy or aralkylsulphonyloxy radicals may
be used. The reaction is preferably performed in the presence of an acid acceptor,
for example an alkali metal alkoxide such as sodium methoxide or potassium tertiary
butoxide in the presence of an corresponding alkanol. The leaving group Z may itself
be formed in situ from the corresponding alkanol (Z = OH) by reaction with a hydrohalogenic
acid (e.g. hydrochloric acid or a Lewis acid such as aluminium chloride: see Japanese
Patent Kokai No. 131577/77) and the resulting agent of formula (I
II) reacted directly with imidazole without prior isolation. Alternatively an alkanol
(Z = OH) or a derivative thereof (e.g. Z = R-A-O-) may be reacted directly with imidazole
(II) by heating in the presence of a dehydrating agent such as phosphoric acid, or
a phosphate (see Japanese Patent Publication No. 5 1105 060), sulphuric acid or sulphates
(see Japanese Patent Publication No. 5 1105 061).
[0013] Among precursor molecules which may be converted to a compound of formula (I) or
an acid addition salt thereof, are substituted imidazole derivatives of formula (IV)
or addition salts thereof
wherein A und R are as defined in formula (I), and
Q , Q
2 and Q
3 are the same or different, at least one being a radical capable of removal by for
example reduction or oxidation, the remaining radical or radicals being selected from
hydrogen or a radical capable of removal in the same or another manner (e.g. a carboxyl
group - see formula (VI) - removed by decarboxylation). Q
1, Q
2 and Q
3 may be selected for example from thio (-SH), alkylthio (-Salkyl wherein alkyl has
1 to 4 carbon atoms) or halo preferably chloro or bromo. The reaction Conditions are
chosen according to the nature of the radicals Q
1, Q2 and Q
3. Desulphurisation may be performed by oxidative or reductive procedures using for
example nitric acid or Raney nickel; and reductive dehalogenation by the use of zinc
and acetic acid or Raney nickel or other reagents known in the literature.
[0014] Another class of examples include carboxy- imidazoles or derivatives thereof of formula
(VI):
wherein A and R are as defined in formula (I), at least one of R
l, R and R
4 is carboxyl or a derivative thereof (for example an ester such as an alkyl ester,
an acid halide such as the chloride, or the nitrile) and the other(s) is hydrogen
or carboxyl or a derivative as described. The compounds of formula (VI) may be converted
into the imidazoles of formula (I) by any suitable decarboxylation conditions which
may simply comprise heating the compounds with or without a catalyst such as copper.
[0015] The imidazoles of formula (I) may also be made from a compound of formula (VII):
wherein (N is 1-imidazoline, 1-imidazole or I-pyrazole, A
1 is a straight or branched saturated or unsaturated acyclic hydrocarbon radical, and
R
3 is a cycloalkyl or cycloalkenyl radical of from 4 to 9 carbon atoms optionally substituted
by alkyl as defined in formula (I), provided that at least one of (N, A
1 and R
3 is other than 1-imidazole, a saturated acyclic hydrocarbon and an optionally substituted
cycloalkyl group respectively as defined in formula (I). Thus an imidazoline (VIII):
wherein one of ---- represents an extra bond, A and R are defined in formula (I) may
be dehydrogenated to the corresponding imidazole in the presence of a catalyst for
example by heating to 250°C in the presence of palladium, nickel or platinum under
pressure, or by heating with a dehydrogenating agent such as selenium or copper oxide.
The 1-pyrazole compounds (VII) may be treated with ultra-violet irradiation, optionally
under an inert atmosphere (e.g. argcn) in for example 1,2-dimethoxyethane at room
or elevated temperatures (see for example "Ring Transformations of Heterocycles" edited
van der Plas, Academic Press, 1973 at page 261). The unsaturated imidazoles of formula
(I) (in formula (
VII), A and/or R
3 are unsaturated) may be reduced to the corresponding saturated compounds with a noble
metal catalyst, for example platinum or palladium in an alkanol.
[0016] The intermediates for use in the above described reactions may also be made by conventional
methods known in the art. Thus the 1-pyrazole and 1-imidazoline intermediates (formula
(VII) may be prepared by alkylation of pyrazole and imidazoline in an analogous manner
to that described above for preparation of the corresponding imidazoles. The intermediates
of formula (III) may be made in known manner preferably by halogenation of the corresponding
alcohols (formula (III), Z = -OH) where in such compounds R is cycloalkenyl, the alcohol
is cnveniently prepared by the Prins reaction from the cycloalkene and paraformaldehyde
(Bull. Chem. Soc. Japan 46/8, 2512-5, 1973). The substituted imidazole intermediates
of formula (IV) may be made in known manner, for example see "Imidazole and its derivatives"
Part I, Ed. K. Hofmann, Interscience Publishers Inc. New York, 1973. For example the
2-thioimidazoles of formula (IV) may be made by cyclisation of an acetal of formula
(IX):
with thiocyanate, wherein R is alkyl.
[0017] The pharmaceutically acceptable addition salts of the compounds of formula (I) may
be prepared by any method known in the art. In particular they may be prepared by
treating the parent imidazole with the appropriate acid.
[0018] Examples of the addition salts of the compounds of formula (I) include those salts
derived from the following acids: oxalic, hydrochloric, hydrobromic, sulphuric, nitric,
perchloric, fumaric, maleic, phosphoric, glycolic, lactic, salicyclic, succinic, toluene-p-sulphonic,
tartaric, acetic, citric, methanesulphonic, formic, benzoic, malonic, naphthalene-2-sulphonic
and benzenesulphonic.
[0019] The imidazoles of formula (I) may be used in conjunction with a phosphodiesterase
inhibitor, which provides a further, synergistic increase in effect, as it acts against
platelet aggregation by a different pathway.
[0020] Suitable phosphodiesterase inhibitors for use in potentiating the anti-aggregatory
effects of the active compounds include as such or as pharmaceutically acceptable
salts:-
(a) Xanthine derivatives such as:-
Theophylline(3,7-dihydro-1,3-dimethyl-lH- purine-2,6-dione), and salts thereof. 3-Isobutyl-l-methyl-xanthine;
Caffeine(3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) and salts thereof; and Aminophylline
(adduct of Theophylline and 1,2-ethanediamine (2:1)).
(b) Isoquinoline derivatives, for example:-
Papaverine(1-[(3,4-dimethoxyphenyl)methyl]-6,7-dimethoxyisoquinoline) and salts thereof;
anc
6,7-Diethoxy-l-(4,5-diethoxybenzyl)isoquinoline or its salts e.g. its hydrochloride;
(c) Derivatives of pyrimido(5,4-d)-pyrimidine, for example:-
Dipyridamole(2,2',2",2"'-(4,8-dipiperidino- pyrimido [5,4-d]pyrimidin-2,6-diyldinitrilo)-tetraethanol)
and its salts;
2,2',2",2"'-[[4-(1-piperidinyl)pyrimido[5,4-d] pyrimidin-2,6-diyl]dinitrilo]tetrakisethanol
and its salts; and
2,4,6-tri-4-morpholinylpyrimido [5,4-d]pyrimidine and its salts.
(d) Derivatives of thieno [3,2-d]pyrimidine, for example:-
N- [4-(4-morpholinyl)thieno]3,2-d [pyrimidin-2-yl]-1,2-ethanediamine.
(e) Derivatives of pyrazolo[3',4':2,3]pyrido-[4,5-b] [1,5] benzodiazepin-6-(3H)-one,
for example:-
3-Ethyl-7,12-dihydro-7,12-dimethylpyrazolo-[4',3':5,6] pyrido [4,3-b]-[1,5]benzodiazepin-6-(3H)-one;
3-Ethyl-7,12-dihydro-9-methoxy-7,12-dimethyl- pyrazolo[3',4':2,3]pyrido[4,5-b][1,5]-benzodiazepin-6-(3H)-one;
and
10-Chloro-3-ethyl-7,12-dimethyl-7,12-dihydro- pyrazoio [4'3':5,6]pyrido[4,3-b][1,5]benzo-
diazepin-6-(3H)-one.
(f) Derivatives of 1H- or 2H-pyrazolo [3,4-b]-pyridine, for example:-
4-(Butylamino)-1-ethyl-1H-pyrazolo [3,4-b]-pyridine-5-carboxylic acid ethyl ester;
4-(Butylamino)-lH-pyrazolo[3,4-b]pyridine-6-carboxylic acid ethyl ester;
4-Chloro-1-ethyl-3-methyl-1H-pyrazolo [3,4-b]-pyridine-5-acetonitrile;
l-Ethyl-4-(isopropylidenehydrazino)-3-methyl-1H-pyrazolo [3,4-b]pyridine-5-carboxylic
acid ethyl ester or its salts such as its hydrochloride hemihydrate; and
2-Methyl-6-phenyl-4-(1-piperidinyl)-2H-pyrazolo-[3,4-b] pyridine or its salts e.g.
its hydrochloride.
(g) Derivatives of 5H-furo- [3,4-e] pyrazolo- |3,4-b|pyridine-5-one, for example:-
4-(Butylamino)-1-ethyl-1,7-dihydro-7-hydroxy-5H-furo-[3,4-e]pyrazolo[3,4-b]pyridine-5-one;
and
(h) Derivatives of 1(2H)-naphthalenone, for example:-
2[(Dimethylamino)methyl] -3,4-dihydro-7-methoxy-1(2H)-naphthalenone or its salts e.g.
its 1:1 hydrochloride.
[0021] The active compounds are particularly useful in the treatment and/or prophylaxis
of thrombo-embolic disorders in mammals, including man. It is to be understood that
the term "thrombo-embolic disorders" includes those disorders whose etiology is associated
with platelet aggregation.
[0022] The active compounds are useful wherever it is desired to inhibit platelet aggregation
and/ or to reduce the adhesive character of platelets, and consequently to treat or
prevent the formation of thrombi in mammals, including man. For example, the compounds
are useful in the treatment and prevention of myocardial infarcts cerebro-vascular
thrombosis and ischaemic peripheral vascular disease; to treat and prevent post-operative
thrombosis; and to promote patency of vascular grafts following surgery.
[0023] The active compounds are also useful as an addition to blood, blood products, blood
substitutes, and other fluids which are used in artificial extra-corporeal circulation
and perfusion of isolated body portions, e.g., limbs and organs, whether attached
to the original body, detached and being preserved or prepared for transplant, or
attached to a new body. It may also be used in laboratory animals, e.g. cats, dogs,
rabbits, monkeys and rats, for these purposes in order to develop new methods and
techniques for organ and limb transplants.
[0024] The active compounds also exhibit some vasodilatory action on blood vessels and therefore
have a utility as anti-hypertensives for the treatment of high blood pressure in mammals,
including man.
[0025] The amount of active compound required for therapeutic or prophylactic effect will
vary with the route of administration, and the nature of the condition under treatment.
In general a suitable dose for a mammal, including man, of active compound will lie
in the range of 0.1 to 300 mg per kg body weight, particularly from 0.5 to 10 mg per
kg body weight, for example 2 mg per kg. A suitable single oral dose for an adult
human lies within the range of 50 to 600 mg, for example 150 mg given say three times
a day.
[0026] While it is possible for the active compounds to be administered as the raw chemical
it is preferable to present them as a pharmaceutical formulation. The formulations,
both for veterinary and for human medical use, of the present invention comprise an
active compound as above defined, together with one or more acceptable carriers therefor
and optionally other therapeutic ingredients. The carrier(s) must be 'acceptable'
in the sense of being compatible with the other ingredients of the formulation and
not deleterious to the recipient thereof. Unit doses of a formulation may contain
between 60 mg and 1.5 g of an active compound.
[0027] The formulations include those suitable for oral, rectal, vaginal or parenteral (including
subcutaneous, intramuscular and intravenous) administration. Preferred formulations
include tablets, capsules and injectable suspensions or solutions.
[0028] The formulations may conveniently be presented in unit dosage form and may be prepared
by any of the methods well known in the art of pharmacy. All methods include the step
of bringing into association the active compound (in the form of the base or a pharmaceutically
acceptable acid addition salt) with the carrier which constitutes one or more accessory
ingredients. In general the formulations are prepared by uniformly and intimately
bringing into association the active compound with liquid carriers or finely divided
solid carriers or both, and then, if necessary, shaping the product into the desired
formulation.
[0029] It will be appreciated from the foregoing that the present invention provides the
following features:-
(a) Novel 1-alkylimidazoles of formula (I), and acid addition salt thereof.
(b) Methods of preparing imidazoles of formula (I) and acid addition salts thereof.
(c) Pharmaceutical formulations containing the imidazoles of formula (I) or an acid
addition salt thereof and a pharmaceutically acceptable carrier.
(d) Method of preparing the pharmaceutical formulations containing the imidazoles
of formula (I) or an acid addition salt thereof.
(e) A method for the treatment or prophylaxis of a thrombo-embolic disorder in a mammal
or mammalian tissue, including man or human tissue, comprising administering an active
compound.
(f) An 1-alkylimidazole of formula (I) or saltthereof as an active agent for the treatment
of a thrombo-embolic disorder in a mammal or mammalian tissue, including man or human
tissue.
[0030] The following Examples are provided by way of an illustration of the present invention
and should in no way be construed as constituting a limitation thereof. All temperatures
are given in degrees Celsius.
EXAMPLE 1
1-Cyclooctylmethylimidazole
[0031] Imidazole (2.0 g, 0.03 mol) was added to a solution of sodium (0.7 g, 0.03 mol) in
dry ethanol (50 ml). The mixture was stirred and heated to boiling when bromomethyl-
cyclooctane (5.5 g, 0.027 mol) was added dropwise. Following the addition, the reaction
mixture was stirred and boiled for 15 h.
[0032] After cooling, the reaction mixture was filtered, and the filtrate concentrated under
reduced pressure. The residue was dissolved in 2M-hydrochloric acid (100 ml) and the
solution washed with ether (25 ml). The aqueous layer was basified with lOM-sodium
hydroxide solution and then extracted with chloroform (3 x 50 ml). The chloroform
extracts were combined and dried (MgS0
4). Evaporation of the chloroform gave an oil which was purified using a silica gel
column and elution with ethyl acetate/methanol (9:1). The product was further purified
by distillation, b.p. 120-122°/0.2 mmHg.
EXAMPLE 2
Preparation of 1-cyclopentylmethylimidazole
[0033] Imidazole (6.8 g, 0.1 mol) was added to a solution of sodium (2.3 g, 0.1 mol) in
dry ethanol (100 ml). This solution was stirred and heated to reflux when bromomethylcyclo-
pentane (16.3 g, 0.1 mol) was added dropwise. Following the addition, the mixture
was stirred and heated under reflux for 16 h.
[0034] After cooling, the reaction mixture was filtered and the filtrate concentrated under
reduced pressure. The residue was dissolved in 2M-hydrochloric acid (150 ml) and the
solution washed with ether. The aqueous solution was basified with 10M-sodium hydroxide
solution, and the product extracted with chloroform (3 x 50 ml). The extracts were
combined, dried (MgS0
4), and the solution concentrated to afford a yellow oil.
[0035] The oil was purified using a silica gel column and elution with ethyl acetate/methanol
(9:1). The product fractions were combined and concentrated under reduced pressure
to afford 1-cyclopentylmethylimidazole (1.9 g), which was further purified by distillation,
b.p. 68-69
0/0.125 mmHg.
EXAMPLE 3
Preparation of 1-(3-cyclopentylpropyl)imidazole
[0036] Imidazole (1.0 g, 0.0147 mol) was added to a solution of sodium (0.34 g, 0.0148 mol)
in dry ethanol (30 ml). This solution was stirred and heated to boiling when 3-bromopropyl-
cyclopentane (2.94 g, 0.0154 mol) was added dropwise. Following the addition, the
reaction mixture was stirred and boiled for 20 h.
[0037] After cooling, the mixture was filtered and the filtrate concentrated under reduced
pressure. The residue was dissolved in 2M-hydrochloric acid (50 ml) and the solution
washed with ether (25 ml). The acid solution was then basified with 10M-sodium hydroxide
solution, and the product extracted with chloroform (3 x 25 ml). The combined extracts
were dried (MgS0
4) and concentrated under reduced pressure to afford a yellow oil (2.1 g).
[0038] The oil was purified by column chromatography (silica gel) using ethyl acetate/methanol
(9:1) as eluent. The product fractions were combined and concentrated to afford 1-(3-cyclo-
pentylpropyl)imidazole which was further purified by distillation, b.p. 89-90
0/0.1 mmHg.
EXAMPLE 4
Preparation of 1-(cycloheptylmethyl)imidazole
[0039] Bromomethylcycloheptane (5.3 g, 0.0278 mol) was added dropwise to a stirred solution
of potassium t-butoxide (3.1 g, 0.0277 mol) and imidazole (1.9 g, 0.0279 mol) in dry
n-butanol (50 ml) maintained at 100° and under dry nitrogen. After the addition (~20
mins) the temperature of the reaction mixture was raised to boiling. The reaction
mixture was then stirred and boiled for 7 h and then cooled.
[0040] The mixture was filtered, and the n-butanol was removed under reduced pressure to
give a pale yellow oil. The oil was dissolved in 2M-hydrochloric acid (100 ml) and
the acid solution was washed with ether (100 ml) and then basified with 10M-sodium
hydroxide solution and the resulting suspension was extracted with chloroform (3 x
50 ml). The chloroform extracts were combined, dried (MgS0
4), and concentrated under reduced pressure to give a pale yellow oil.
[0041] The oil was purified using a silica gel column and elution with ethyl acetate/methanol
(9:1). Concentration of the fractions containing 1-(cycloheptylmethyl)imidazole gave
a pale yellow oil which was further purified by distillation, b.p. 92-94
0/0.1 mmHg.
EXAMPLE 5
Preparation of 1-(2-cyclooctenylmethyl)imidazole
(a) Preparation of 2-cyclooctene-1-methanol using the Prins reaction (Uchida et aZ.,
Bull. Chem. Soc., Japan, 1973 46, 2512)
[0042] Cyclooctene (69.0 g, 0.63 mol) was added dropwise, to a stirred suspension of paraformaldehyde
(24.0 g) in 98% formic acid (100 ml). After the addition, the reaction mixture was
stirred and heated under reflux for 2 h. Water (100 ml) was then added, and the aqueous
solution was extracted with ether (50 ml). The ether solution was washed with saturated
sodium bicarbonate solution (5 x 50 ml), with water (2 x 50 ml), and then dried (MgS0
4). Concentration under reduced pressure afforded a brown oil which was purified by
distillation, the fraction b.p. 80-110°/24 mmHg being retained.
[0043] A portion of the aforesaid oil (10 g) was treated with Claisen's alkali [potassium
hydroxide (10 g), methanol (31.2 ml) and water (8 ml)], and the reaction mixture was
then boiled for 2 h.
[0044] After cooling, the mixture was poured onto iced-water (50 ml) and extracted with
ether (3 x 50 ml). The ether extracts were combined and dried (MgS0
4). Concentration of the solution under reduced pressure afforded an oil which was
distilled, to afford 2-cyclooctene-l-methanol, b.p. 128-130
0/23 mmHg.
(b) Preparation of 2-cyc1ooctene-1-bromomethane
[0045] A solution of phosphorus tribromide (1.02 ml, 0.0105 mol) in petroleum ether (b.p.
40-60°, 5 ml) was added dropwise to a stirred solution of 2-cyclooctene-1-methanol
(2.8 g, 0.02 mol) and dry pyridine (0.104 g, 0.0013 mol) in petroleum ether (b.p.
40-60°; 15 ml) at -10°. After the addition, the reaction mixture was set aside at
ambient temperature for 48 h.
[0046] The reaction mixture was treated with water (50 ml) and the organic layer separated.
The aqueous solution was extracted with petroleum ether (b.p. 40-60°, 3 x 25 ml) and
the organic layer and petroleum ether extracts combined, washed with 2M-sodium hydroxide
solution (25 ml), and with water (25 ml), and then dried (MgS0
4). Concentration of the solution under reduced pressure gave an oil (2.3 g) which
was distilled, b.p. 48-50°/0.25 mmHg.
(c) Preparation of 1-(2-cyclooctenylmethyl)imidazole
[0047] 2-Cyclooctene-1-bromomethane (0.7 g, 0.0034 mol) was added dropwise to a boiling
solution of imidazole (0.24 g, 0.0035 mol) and potassium t-butoxide (0.39 g, 0.0035
mol) in dry n-butanol, under dry nitrogen. After the addition, the reaction mixture
was stirred and heated under reflux for 1 h. The pure product was obtained as described
in Example 4, b.p. 108-110°/0.02 mmHg.
EXAMPLE 6
Preparation of 1-(4-methylcyclohexylmethyl)imidazole
[0048] 1-Bromomethyl-4-methylcyclohexane (3.1 g, 0.0162 mol) was added dropwise to a stirred,
boiling solution of imidazole (1.12 g, 0.0165 mol) and potassium t-butoxide (1.85
g, 0.0165 mol) in dry n-butanol, under dry nitrogen. After the addition, the reaction
mixture was stirred and heated under reflux for 10 h.
[0049] After cooling, the reaction mixture was filtered, and then concentrated under reduced
pressure. The residue was dissolved in 2M-hydrochloric acid (100 ml) and the solution
was washed with ether (50 ml). The acid solution was basified with 10M-sodium hydroxide
solution and extracted with chloroform (3 x 50 ml). The combined chloroform extracts
were dried (MgS0
4) and concentrated under reduced pressure. The oily residue was purified using a silica
gel column and elution with ethyl acetate/methanol (9:1). The fractions containing
1-(4-methylcyclohexylmethyl)imidazole were combined, concentrated, and the resulting
oil distilled, b.p. 80
0/0.125 mmHg.
EXAMPLE 7
Biological Results
[0050] Horse platelets were prepared from whole horse blood by differential centrifugation.
Approximately 10 platelets were homogenised in 1 ml 100 mM Tris buffer pH 7.4. Various
concentrations of active compound were added and the reaction sets incubated for 5
minutes at ambient temperature. To each tube was added 20 nM of arachidonic acid containing
10
6 DPM of labelled arachidonic acid and the tubes incubated for 3 minutes at 37°C in
a shaking water bath. After incubation the radioactive products were extracted from
the acidified aqueous phase with ethyl acetate and after concentration resolved by
thin layer chromotography on silica gel with chloroform/ methanol/acetic acid/water
(90:8:1:0.8) as a developing solvent. The amount of thromboxane produced was measured
by scraping the radioactive zone corresponding to thromboxane B
2 and estimating the radioactivity in a liquid scintillation counter.
[0051] The concentration of active compound to reduce the enzyme activity by 50% (ED
50) was established. The results are shown in Table A.
[0052] The selectivity of the active compounds was measured in a similar manner to that
described above and the amount of PGE, PGF and PGD produced was determined. The greater
the selectivity, the more of the prostaglandins are produced indicating lower inhibition
of cyclo-oxygenase.
[0053] The ED
SO and Selectivity results are shown in Table A in which 0 indicates no selectivity;
+ low selectivity; ++ medium selectivity; and +++ high selectivity, and ++++ exceptionally
high selectivity.
Example 8 - Tablet formulation
[0054] The imidazole salt is ground to a fine powder, blended with the starch and then the
mixture granulated with an aqueous solution of the polyvinylpyrrolidone. The granules
are sieved 1000 µ, dried, sieved again and the magnesium stearate added. The mixture
is then compressed into tablets.
[0055] In the same manner, tablets of 1-cyclohex-3-enylmethylimidazole and 1-cyclohexylethylimidazole
are prepared.
Example 9 - Tablet formulation
[0056] Tablets (150 mg) of the imidazoles described in the preceding example are prepared
as in the same manner from the following ingredients:
[0057] In the preparation, the lactose is blended with the starch.
Example 10 - Tablet formulation
[0058] Tablets (100 mg) of the imidazoles of Example 8 are prepared in the same manner from
the following ingredients:
Example 11 - Tablet formulation
[0059] Tablets (150 mg) of the imidazoles of Example e are prepared in the same manner from
the following ingredients, except that the starch, pregelled starch and imidazole
compound are all blended together prior to granulation:
Example 12 - Injectable formulation
[0060] Imidazole compound of formula (I) 15.0 g Lactic Acid B.P. q.s. to pH 3.0 Water for
Injections B.P. to 100.0 ml
[0061] Suspend the compound in of the available quantity of water. Add sufficient Lactic
Acid to dissolve the compound and to reduce the pH t) 3.0.
[0062] Dilute to volume with Water for Injections.
[0063] Sterilise the solution by passage through a membrane filter, pore size 0.22 µm.
[0064] Distribute the solution using aseptic precautions into sterilised ampoules, 1 ml
per ampoule. Seale by fusion of the glass.
[0065] Each 1 ml ampoule supplies 150 mg of the imidazole compound: 1-cyclooctylmethylimidazole
fumarate
Example 13 - Injectable formulation
[0066]
[0067] Suspend the compound in the final volume of Water for Injections. Add sufficient
Citric Acid as a 10% solution in Water for Injections to dissolve the compound andreduce
the pH to 3.0. Dilute to volume with Water for Injections.
[0068] Sterilise the solution by passage through a membrane filter, pore size 0.22 pm.
[0069] Distribute the solution with aseptic precautions into sterilised vials, 25 ml per
vial. Stopper with sterile rubber closures and seal with an aluminium cap.
[0070] Each 1 ml of solution provides 150 mg of the compound: 1-cyclooctylmethylimidazole
fumarate.
Example 14 - Injectable formulation
[0071] In the manner described in the preceding two Examples, injectable formulations of
1-cyclohexylethylimidazole and 1-cyclohex-3-enylmethylimidazole salts were prepared.
EXAMPLE 15
[0072] By the method described in Example 1 above the following compounds were prepared:-
(a) 1-(cyclooctylvinyl)imidazole
(b) 1-(2-cyclooctylethyl)imidazole
(c) 1-(cyclooctylethyl)imidazole
(d) 1-(3-cyclooctylpropyl)imidazole
(e) 1-(3-methylcyclohept-2-enylmethyl)imidazole
(f) 1-(3-methylcycloheptylmethyl)imidazole
(g) 1-(cyclohex-3-enylmethyl)imidazole m.p. 36-37°C
(h) 1-(cyclohexylethyl)imidazole b.p. 95-96/0.2 mm
(i) 1-(cyclobutylmethyl)imidazole b.p. 148-150/25 mm.
(j) 1-(cyclononylmethyl)imidazole
Example 16 - Salts of 1-Cycloocty3-methylimidazole
A. Hydrogen Fumarate
[0073] A solution of fumaric acid (0.22 g) in hot ethanol (10 ml) was added to a solution
of 1-cyclooctylmethylimidazole (0.38 g) in ethanol (4 ml). After boiling for 10 minutes
the solution was evaporated to afford a white solid. Recrystallisation from ethyl
acetate afforded 1-cyclooctylmethylimidazole hydrogen fumarate (0.42 g) as white needles,
m.p. 147-148°.
B. Hydrogen Succinate
[0074] A solution of succinic acid (0.23 g) in ethanol (~5 ml) was added to a solution of
1-cyclooctylmethylimidazole (0.38 g) in ethanol (5 ml). Evaporation of the solution
afforded a white solid. Recrystallisation hydrogen succinate of the solid from ethyl
acetate afforded 1-cyclooctylmethylimidazole/(0.27 g) as colourless plates,
m.p. 86-87°.
C. Oxalate
[0075] A solution of oxalic acid (0.17 g) and 1-cyclooctylmethylimidazole (0.38 g) in ethanol
(20 ml) was boiled for 0.25 h, when evaporation of the solution afforded a white solid.
Recrystallisation of the solid from ethyl acetate/ethanol/petroleum ether (b.p. 40-60°)
afforded 1-cyclooctylmethylimidazole oxalate as white needles, m.p. 141-142°-.
D. Hydrochloride
[0076] 1-Cyclooctylmethylimidazole (~ 0.3 g) was dissolved in dry ether (30 ml), when a
stream of dry hydrogen chloride was passed through the solution at -20°. The resulting
white precipitate was filtered off under dry nitrogen and recrystallised from ethyl
acetate/petroleum ether (b.p. 40-60°) to afford 1-cyclooctylmethylimidazole hydrochloride
as a white solid, m.p. 20-22°C.