Polyene compounds useful in the treatment of allergic responses

Polyene compounds represented by the formula ##STR1## where R is H or lower alkyl of from 1 to 5 carbon atoms; PA0 R.sub.1 is H, lower alkyl of from 1 to 8 carbon atoms or aralkyl; and PA0 R.sub.2 is (CH.sub.2).sub.n CH.sub.2 OH, CHO or CO.sub.2 R; wherein n is 1 or 2. The foregoing compounds have been found active in regulating the formation of lipoxygenase and as such possess therapeutic value in the treatment of inflammatory conditions and allergic responses.

BACKGROUND OF THE INVENTION 
The present invention relates to polyene compounds and more particularly to 
dienoic compounds derived from aryl intermediates with the general 
formulae: 
##STR2## 
where 
R is H or lower alkyl of from 1 to 5 carbon atoms 
R.sub.1 is H, lower alkyl of from 1 to 8 carbon atoms or aralkyl. 
A synthesis of methyl 
7-(4-methoxy(-2,3,6-trimethylphenyl)-5-methyl-hepta-2,4,6-trienate is 
described in U.S. Pat. No. 4,534,979. A synthesis of 
2,3,6-trimethyl-p-anisaldehyde is described in U.S. Pat. No. 4,105,681. 
Other prior art publications include U.S. Pat. No. 4,137,246 and Swiss Pat. 
No. 616,134 describing the synthesis of certain pentadienals and esters of 
pentadienoic acids of the following formula as intermediates useful in the 
preparation of antitumour polyenoic agents: 
##STR3## 
where 
R is formyl and CO.sub.2 CH.sub.3. 
U.S. Pat. No. 4,534,979 describes the synthesis of 
5-(2,3-dimethyl-4-methoxy-phenyl)-3-methyl-2,4-pentadien-1-al as 
intermediate for the preparation of anti-psoriasis and anti-allergy 
polyenes. M. P. Reddy, et al. (Synthesis, 1980, (10), 815-18) describes 
the synthesis of some 5-aryl-3-methyl-2(E)-pentadienals and their 
oxidation to pentadienoic acids. 
SUMMARY OF THE INVENTION 
The present invention is directed to polyene compounds of the general 
formula 
##STR4## 
where 
R is H or lower alkyl of from 1 to 5 carbon atoms; 
R.sub.1 is H, lower alkyl of from 1 to 8 carbon atoms or aralkyl; and 
R.sub.2 is (CH.sub.2).sub.n CH.sub.2 OH, CHO or CO.sub.2 R; wherein n is 1 
or 2. 
DETAILED DESCRIPTION OF THE INVENTION 
The compounds of the formula I in which R.sub.2 is (CH.sub.2).sub.n 
CH.sub.2 OH are prepared by reacting a compound of formula 
##STR5## 
with a reducing agent, such as lithium aluminum hydride, in an organic 
solvent such as ethyl ether or tetrahydrofuran (THF); 
wherein R.sub.3 is CHO, OH or CO.sub.2 R; and R, R.sub.1, and n are the 
same as described in formula I. 
Compounds of formula I in which R.sub.2 us CO.sub.2 R are prepared by 
reacting compounds of formula 
##STR6## 
with a Horner reagents of formula 
##STR7## 
in the presence of sodium hydride or sodium amide in an organic solvent 
such as THF; 
wherein the formulae III and IV, R, R.sub.1, and n are the same as 
described in formula I, and in formula IV, m is 0-1. 
The compounds of the formula I in which R.sub.2 is CHO are prepared by 
reacting a compound of formula 
##STR8## 
with Vilsmeier reagent (POCl.sub.3 /N,N-dimethylformamide), wherein in 
formula V, R.sub.4 is H or methyl.

The preferred methods of synthesizing the compounds of the invention are 
described in the Examples that follow. 
EXAMPLE 1 
7-(4-Methoxy-2,3,6-trimethylphenyl)-5-methylhepta-4,6-diene-1-al 
##STR9## 
To a suspension of lithium aluminum hydride (400 mg) in 25 mL of diethyl 
ether stirred under nitrogen in an ice bath was added dropwise a solution 
of methyl 
7-(4-methoxy-2,3,6-trimethylphenyl)-5-methylhepta-2,4,6-trienoate (2.1 g, 
7 mmol) in 20 mL of diethyl ether and 5 mL of tetrahydrofuran. The mixture 
was stirred for 41/2 hrs while its temperature was allowed to rise slowly 
to room temperature. Water (0.3 mL) was added dropwise to the mixture with 
stirring; a white precipitate occurred, which was removed by filtration. 
The filtrate was dried (Na.sub.2 SO.sub.4) and concentrated in vacuo to 
give 2.2 g of pale yellow oil. This crude mixture was purified by a column 
chromatography (silica gel, 20% ethyl acetate in hexane) to afford 0.9 g 
of pure 7-(4-methoxy-2,3,6-trimethylphenyl)-5-methylhepta-4,6-diene-1-al 
as pale yellow oil. Crystallization from ethyl acetate/hexane gave white 
crystals: mp 42.degree.-45.degree. C.; MS (EI): 275 (m.sup.+ +1); NMR 
(COCl.sub.3) .delta.5.40 (m. 3H), 6.00 (d,j=16 Hz,1H) 6.33 (d,j=16 Hz, 
1H), 6.46 (s, 1H). 
EXAMPLE 2 
Ethyl 4-methoxy-2,3,6-trimethylcinnamate 
##STR10## 
A suspension of NaH (9.3 g, 50% dispersion in oil, 0.19 mol) in 150 mL of 
tetrahydrofuran (THF) was stirred in an ice bath under an atmosphere of 
nitrogen and triethyl phosphonoacetate (43.5 g, 0.19 mol) was added 
dropwise within 15 min. The mixture was stirred for 1 hr in the ice bath 
and a solution of 2,3,6-trimethyl-p-anisaldehyde (24.3 g, 0.14 mol) in 100 
mL of THF was added. The resulting mixture was stirred at room temperature 
for 18 hrs and brine (250 mL) and ethyl acetate (250 mL) was added. The 
layers were separated; the organic layer was washed with brine and dried 
(Na.sub.2 SO.sub.4). Removal of solvent in vacuo afforded 32.3 g of yellow 
oil. A small portion of this product was recrystallized from ethyl ether 
to give white powders: mp 42.degree.-44.degree. C.; MS(CI): 249(m.sup.+ 
+1), 203. The rest of the product was used in the reaction described in 
Example 3 without further purification. 
EXAMPLE 3 
4-(4-Methoxy-2,3,6-trimethylphenyl)-2-methyl-3-buten-2-ol 
##STR11## 
In a 3-necked, 250 mL round-bottomed flask, equipped with a nitrogen-inlet, 
a stopper and a low-temperature thermometer, was placed 28 mL of an 
ethereal solution of methyl magnesium bromide (2.9 molar solution, 0.08 
mol). The stirred Grignard reagent was cooled to about -10.degree. C. and 
a solution of ethyl 4-methoxy-2,3,6-trimethylcinnamate (4.9 g, 0.02 mol) 
in 35 mL of ethyl ether was added dropwise within 15 min. The resulting 
mixture was then stirred at room temperature for 18 hrs and heated to a 
gentle reflux for 2 hrs. The mixture was cooled in an ice bath and 15 mL 
of ice-cold water was added, followed by 5% aqueous NaHCO.sub.3 solution. 
The mixture was extracted with ethyl ether; the combined ethereal solution 
was washed with brine and dried over Na.sub.2 SO.sub.4. Removal of solvent 
in vacuo yielded a yellow oil, crystallization from ethyl ether-petroleum 
ether gave 3.64 g of white powders: mp 53.degree.-57.degree. C. 
EXAMPLE 4 
5-(4-Methoxy-2,3,6-trimethylphenyl)-3-methyl-2,4-pentadien-1-al 
##STR12## 
A solution of 4-(4-methoxy-2,3,6-trimethylphenyl)-2-methyl-3-buten-2-ol 
(3.98 g, 0.017 mol) in 8 mL of N,N-dimethylformamide (DMF) was stirred in 
an ice bath and the Vilsmeier reagent, which was prepared from 2.1 mL (3.4 
g, 0.022 mol) of phosphoryl chloride and 3.5 mL of DMF at about 10.degree. 
C., was added dropwise. The temperature of the reaction mixture was 
allowed to rise to 80.degree. C. within 1 hr. The mixture was stirred for 
3 hrs at 80.degree. C. and, with cooling (ice bath), a solution of sodium 
acetate (10g) in 25 mL of water was added dropwise. The resulting mixture 
was heated to 80.degree. C. for 10 min. After cooling to room temperature, 
the product was extracted into ethyl ether. Removal of solvent in vacuo 
afforded an orange-colored substance. Crystallization from ethyl 
acetate-ethyl ether gave 2.2 g of the title compound as yellow crystals: 
mp 62.degree.-64.degree. C. 
EXAMPLE 5 
Ethyl 5-(2,3-Dimethyl-4-methoxyphenyl)-2,4-pentadienoate 
##STR13## 
In a manner similar to Example 2, 16.5 g (0.1 mol) of 
2,3-dimethyl-4-methoxybenzaldehyde was treated with triethyl 
phosphonocrotonate (30 g, 0.12 mol) in a modified Wittig reaction to give 
a yellow oil. Purification by a silica gel dry column (20% ethyl acetate 
in hexane) to give 12 g of the title compound as a yellow powder: mp 
92.degree.-95.degree. C. 
EXAMPLE 6 
5-(2,3-Dimethyl-4-methoxyphenyl)-2,4-pentadienoic Acid 
##STR14## 
A solution of ethyl 5-(2,3-dimethyl-4-methoxyphenyl)-2,4-pentadienoate (2 
g, 7.7 mmol) in 10 mL of ethanol was stirred at room temperature under 
nitrogen and a solution of KOH (1 g) in 2 mL of water was added dropwise. 
The mixture was stirred at room temperature for 18 hrs. and concentrated 
in vacuo. The residue was diluted with water and extracted several times 
with ethyl ether. The aqueous layer was acidified to pH 3 with a 10N HCl 
solution. The resulting yellow precipitate was extracted into ethyl 
acetate. The organic solution was washed with brine and dried (Na.sub.2 
SO.sub.4). Evaporation in vacuo afforded a yellow powder. Crystallization 
from ethyl acetate/ethyl ether gave 1.1 g of yellow crystals: MS (CI): 233 
(M+1).sup.+, 215. 
Compounds of the present invention were found to have potent activity in 
regulating the formation of lipoxygenase and as such possess therapeutic 
value in the treatment of inflammatory conditions and allergic responses 
such as anaphylaxis and asthma. 
Lipoxygenases in mammals have been found in the lung, platelets, and white 
cells. They are enzymes capable of oxidizing arachidonic acid into 
hydroperoxyeicosatetraenoic acids (HPETEs) and their stable products 
hydroxyeicosatetraenoic acids (HETEs). Lipoxygenases are classified 
according to the position in the arachidonic acid which is oxygenated. 
Platelets metabolize arachidonic acid to 12-HETE, while polymorphonuclear 
leukocytes contain 5 and 15 lipoxygenases. It is known that 12-HETE and 
4,12-diHETE are chemotactic for human neutrophils and eosinophils, and may 
augment the inflammation process, 5-HPETE is known to be a precursor of 
slow-reacting substance of anaphylaxis (SRS-A). The SRS family of 
molecules, such leukotrienes B, C, and D, have been shown to be potent 
bronchoconstrictors (see, NATURE 288, 484-486 (1980)). 
Protocol I describes an assay to detect inhibitors of the lipoxygenase 
pathway. Such inhibitors are believed to be capable of modulating the 
biosynthesis of the leukotrienes, a property believed to be useful in 
treating asthma and inflammatory disease states. 
PROTOCOL I 
A suspension of rat neutrophils in buffer is incubated for 3 minutes at 
30.degree. C. with [.sup.14 C]-arachidonic acid (AA) and Calcium Ionophore 
A23187. Citric acid (2M) is used to quench the reaction. Following the 
addition of a trace amount of (.sup.3 H)-5-HETE together with an excess of 
unlabeled 5-HETE to each tube, the mixture is extracted with 
chloroform/methanol. The organic layer is washed with dilute acid and an 
aliquot is transferred to glass tubes and dried. The residue is dissolved 
in a small volume of chloroform and an aliquot is spoted on silica gel TLC 
sheets, which are developed with an ethyl acetate/isooctane/water acetic 
acid solvent system. The 5-HETE spots are visulaized with iodine, cut out 
and placed in scintillation vials for counting. After adjusting for the 
extraction efficiency, the amount (pmole) of [.sup.14 C]-5-HETE in each of 
the tubes is quantitated. The net pmoles of 5-HETE are obtained by 
subtracting the pmoles of 5-HETE in the tubes containing buffer alone 
(blank) from the pmoles of 5-HETE in the tubes containing buffer and cells 
(control). The ability of the test compounds to modulate the activity of 
this enzyme is determined by a decrease or increase in the net amount of 
5-HETE produced. 
The concentration required for inhibition of the 5-lipoxygenase pathway 
(5-Lox/I.sub.50 .mu.M) for the compound of the Example 1 is 11 .mu.M. 
(Standard used: all-trans retinoic acid: 90 .mu.M 
Ro 10-9359: 10.+-.17% I at 50 .mu.M 
Ro 11-1430: 11.+-.19% I at 50 .mu.M) 
PROTOCOL II 
In Vitro Assay For Inhibitors of Phospholipase A.sub.2 Assayed at pH 7.0 
(PLA.sub.2) 
The PLA.sub.2 employed in this screen is obtained by aggregation of 
purified rat platelets. In the enzyme assay phosphatidylcholine having 
.sup.14 C-labeled palmitate residues at R.sub.1 and R.sub.2 is employed as 
substrate. PLA.sub.2 acts by cleaving the R.sub.2 fatty acid ester bond 
yielding free fatty acid and lysophosphatidylcholine as follows: 
##STR15## 
Following completion of the reaction, the assay medium is acidified and 
extracted with hexane, which takes up unreacted substrate and free fatty 
acid product. The hexane extract is passed over a short silica column 
which retains 99% of the phosphatidylcholine. The .sup.14 C-labeled 
palmitic acid is not retained (90% recovery in eluate) and is collected 
directly in scintillation counting vials. The released palmitic acid is 
conveniently quantitated by liquid scintillation spectrometry. 
The compounds were tested at 100 .mu.M in a buffer containing 0.3 mM 
unlabeled phosphatidylcholine (PC), 20-30,000 cpm of .sup.14 C(CPC), 100 
.mu.M NaCl, 1 mM CaCl.sub.2 and 50 mM tris-HCl adjusted to pH 7.2 with 1N 
NaOH. This resulted in a buffer at pH 7.2. The temperature of the buffer 
was maintained at a temperature of 37.degree. C. The reaction was 
initiated by addition of the enzyme and it was terminated 30 minutes later 
by the addition of 100 ml of 1N HCl. 
Following acidification, the samples were extracted with 2 ml of 2-propanol 
and 2 ml of hexane, vortexed and allowed to stand until the phases 
separated. Free fatty acids (FFA) and some unreacted substrate were taken 
up in the isopropanol-saturated hexane. The hexane phase of the extraction 
mixture was transferred to a short silica gell column which retained 
reacted PC but not the FFA. The column effluent was collected directly in 
scintillation vials. The columns were washed once with an additional 2 ml 
of hexane. The radio labeled FFA were quantitated by liquid scintillation 
spectrometry. 
The compound of the Example 1 showed a phospholipase A.sub.2 inhibition 
activity of 58 .mu.M at I.sub.50 
(Standard used: all-trans retinoic acid: 32% I at 100 .mu.M) 
The therapeutic agents of this invention may be administered alone or in 
combination with pharmaceutically-acceptable carriers, the proportion of 
which is determined by the solubility and chemical nature of the compound, 
chosen route of administration and standard pharmaceutical practice. For 
example, they may be administered orally in the form of tablets or 
capsules containing such excipients as starch, milk, sugar, certain types 
of clay and so forth. They may be administered orally in the form of 
solutions which may contain coloring and flavoring agents or they may be 
injected parenterally, that is intramuscularly, intravenously or 
subcutaneously. For parenteral administration, they may be used in the 
form of a sterile solution containing other solutes, for example, enough 
saline or glucose to make the solution isotonic. When applied topically 
for treating skin disorders, the present new products can be provided in 
the form of dusting powders, aerosol sprays, ointments, aqueous 
compositions including solutions and suspensions, cream lotions and the 
like. In this regard, any of the commonly employed extending agents can be 
used depending on the nature of the product as is well-known in the art. 
The physician will determine the dosage of the present therapeutic agents 
which will be most suitable and it will vary with the form of 
administration and the particular compound chosen, and furthermore, it 
will vary with the particular patient under treatment. He will generally 
wish to initiate treatment with small dosages substantially less than the 
optimum dose of the compound and increase the dosage by small increments 
until the optimum effect under the circumstances is reached. It will 
generally be found that when the composition is administered orally, 
larger quantities of the active agent will be required to produce the same 
effect as a smaller quantity given parenterally.