5-(3,5-disubstituted phenylazo)-2-hydroxybenzene-acetic acids and salts and lactones thereof having a potentially inhibitory effect on 15-hydroxy-prostaglandin dehydrogenase

The present invention is concerned with azo compounds having the structure ##STR1## in which: Y is hydrogen, and PA0 X and Z are carboxy or lower alkoxycarbonyl, or the lactones or salts of said azo compound, such compounds being useful in pharmaceutical compositions and being specifically useful to inhibit 15-prostaglandin dehydrogenase (PGDH).

The present invention is concerned with novel compounds having a 
potentially inhibitory effect on 15-hydroxyprostaglandin dehydrogenase 
(PGDH). The invention is also concerned with the production of these novel 
compounds and with pharmaceutical compositions containing them. 
The future potentialities of PGDH inhibitors, in respect of their 
usefulness in medicine, have not yet been fully explored. But it is a 
known fact that prostaglandins play a very important role in the body's 
regulating system, and for this reason any drugs interfering with either 
the synthesis or the degradation of prostaglandins may be potentially 
valuable medical tools. The so-called cytoprotective effect of 
prostaglandins is relatively well known in the context of ulcer therapies; 
but neverthless prostaglandin administration has not been utilized to any 
major extent for therapeutic purposes because the prostaglandins 
administered with survive in vivo for only a very short time. A drug 
inhibiting the degradation of endogenous prostaglandins might conceivably 
be much more successful than prostaglandin administration. 
Endogenous prostaglandins have a major role also in inflammatory processes. 
In the treatment of rheumatoid arthritis it is therefore at present quite 
a common practice to employ inhibitors of prostaglandin synthesis; but 
nowadays this is regarded as merely being a symptomatic treatment, and as 
a matter of fact some of the prostaglandins are now believed to possibly 
have a very favorble effect. Thus in this context, too, the inhibition of 
PGDH dependent degradation may be potentially very valuable. Further 
potentially valuable medical fields of application for the present novel 
compounds are all those where prostaglandins may function as desirable 
controlling factors as e.g. in the case of circulatory disorders, cancer, 
fertility, cell regulation etc. 
Examples of previously known compounds having an inhibitory effect on PGDH 
are such azo compounds as are set forth in No. EP-A-21229 and novel 
arylacetic acid derivatives set forth in Swedish patent application No. 
8400239-3. 
It is an object of the present invention to provide improved PGDH 
inhibitors and methods for their production. Further objects are to 
provide improved pharmaceutical compositions and treating methods 
involving such inhibitors. 
The novel compounds of the present invention have the following structure: 
##STR2## 
in which X, Y and Z are hydrogen, carboxy or lower alkoxycarbonyl, one of 
X, Y and Z always being hydrogen and the others being identical or 
different groups. 
The invention comprises also lactones of compounds (I) and salts thereof. 
The preferred salts are pharmaceutically acceptable and therapeutically 
active. 
By lower alkoxy groups are meant those having less than seven carbon atoms. 
Suitable salts are metal salts such as the sodium, potassium and calcium 
salts, or salts with organic amines such as e.g. diethanolamine, 
triethanolamine, N-methyl-glucamine, trishydroxymethyl-methylamine etc. 
A major advantage of the compounds according to the present invention 
resides in that they comprise groups greatly varying inter se in respect 
to their capacity of being absorbed from the gastrointestinal tract. This 
means that the invention comprises i.a. compounds which are rapidly and 
completely absorbed into the bloodstream--which is a valuable feature for 
obtaining a systemic effect. Other compound, on the other hand, have a 
very low capacity for being absorbed and consequently will concentrate to 
the gastrointestinal tract; so this in turn means that some compunds of 
formula (I) may have a potential local activity against gastrointestinal 
disorders such as for instance gastric ulcer, Crohn's disease and ulcerous 
colitis. 
It has been found, surprisingly, that the novel compounds are extremely 
potent inhibitors of the enzyme PGDH. Moreover an important feature of 
these compounds is that they are highly selective in their effect: Their 
inhibition of cyclooxygenase is practically zero. The invention permits 
treatments with very low doses of the active substance, which in turn 
means that particular ways of administration may be resorted to that would 
otherwise be entirely out of the question--e.g. inhalation of the 
substance in the form of an aerosol. The extremely high potency of the 
novel compounds moreover minimizes the risk of toxic side effects due to 
metabolites, especially metabolites of the aromatic amine type formed by 
splitting of the azo bridge. 
The compounds of formula (I) are produced in a manner known per se by 
diazotation of amines of the general formula 
##STR3## 
in which X, Y and Z have the same meanings as above, and coupling with 
2-hydroxybenzeneacetic acid in an alkaline medium, followed by rapid 
neutralization and isolation of the product. 
A compound of formula (I) may be converted to the corresponding lactone of 
the general formula 
##STR4## 
or a lactone of formula (III) may be converted to a compound of formula 
(I). 
Conversion to the lactone may be performed in a simple manner by reaction 
with acids, if desired in the presence of water-withdrawing agents such as 
e.g. acetic anhydride or thionyl chloride, or under other conditions that 
will remove water such as e.g. azeotropic distillation of water. 
The lactones according to the invention can readily be converted to 
corresponding acids by gentle alkaline hydrolysis and subsequent 
acidification. 
A compound of this invention containing at least one free carboxy group B 
readily convertible to corresponding salts by reaction with an equivalent 
amount of a suitable salt-forming reagent such as for example sodium 
hydroxide, potassium hydroxide or a suitable organic amine, at a pH 
suitable for the compound contemplated and in the presence of a solvent. 
The salt may be prepared either in a solid state by means of solvent 
removal in a known per se manner, or if solubility permits directly in 
solution, preferably aqueous solution, for direct pharmaceutical use. 
The novel pharmaceutical compositions of this invention contain a 
therapeutically active amount of a compound of formula (I) or a lactone 
thereof or a salt of those compounds that contain at least one carboxy 
group, if desired in combination with an inert, organic or inorganic 
carrier material which is suitable for oral, rectal, buccal or parenteral 
administration or for inhalation. The pharmaceutical compositions may be 
prepared in solid form or may be semisolid or liquid; optionally they may 
be sterilized and/or contain additional adjuvants. They may be produced in 
a manner well known to persons skilled in the art, the active substance 
being mixed with the carrier material and with further adjuvants (if any), 
and the resultant mixture being converted to a suitable galenic form. As a 
general guideline for suitable dosages may be mentioned doses of 0.01-100 
mg/day for a person weighing 75 kg. 
According to the novel treating method of this invention for the inhibition 
of PGDH, a pharmaceutical composition containing a therapeutically active 
amount of a compound of formula (I) or a lactone thereof or a salt of 
those compounds that contain at least one carboxy group is administered to 
a mammal, including man. 
The compound of this invention may be for instance 
5-(3,5-dicarboxy-phenylazo)-2-hydroxy-benzeneacetic acid, its lactone and 
salts thereof 
the corresponding 3-monomethyl ester, its lactone and salts thereof 
the corresponding 3,5-dimethyl ester, its lactone and salts thereof 
the corresponding 3-monoethyl ester, its lactone and salts thereof 
the corresponding 3,5-diethyl ester, its lactone and salts thereof 
the corresponding 3-ethyl-5-methyl ester, its lactone and salts thereof 
the corresponding 3-propyl ester, its lactone and salts theeof 
the corresponding 3-isopropyl ester, its lactone and salts thereof 
the corresponding 3,5-dipropyl ester, its lactone and salts thereof 
the corresponding 3-butyl ester, its lactone and salts thereof 
the corresponding 3-isobutyl ester, its lactone and salts thereof 
the corresponding 3-pentyl ester, its lactone and salts thereof 
the corresponding 3-hexyl ester, its lactone and salts thereof 
5-(3,4-dicarboxy-phenylazo)-2-hydroxy-benzeneacetic acid, its lactone and 
salts thereof 
the corresponding 3-monomethyl ester, its lactone and salts thereof 
the corresponding 4-monomethyl ester, its lactone and salts thereof 
the corresponding 3,4-dimethyl ester, its lactone and salts thereof 
the corresponding 3-monoethyl ester, its lactone and salts thereof 
the corresponding 4-monoethyl ester, its lactone and salts thereof 
the corresponding 3,4-diethyl ester, its lactone and salts thereof 
the corresponding 3-ethyl-4-methyl ester, its lactone and salts thereof 
the corresponding 3-methyl-4-ethyl ester, its lactone and salts thereof 
the corresponding 3-propyl ester, its lactone and salts thereof 
the corresponding 4-propyl ester, its lactone and salts thereof 
the corresponding 3-isopropyl ester, its lactone and salts thereof 
the corresponding 4-isopropyl ester, its lactone and salts thereof.

The below working examples illustrate various embodiments of the invention 
without limiting its scope. 
EXAMPLE 1 
5-(3,4-bis-(methoxycarbonyl)-phenylazo)-2-hydroxy-phenylacetic acid 
24 g of dimethyl-4-nitro-benzene-1,2-dicarboxylate was dissolved in 500 ml 
of acetic acid, whereupon 2 g of 10% palladium on carbon, suspended in 10 
ml of hydrochloric acid, was added. 
The suspension was hydrogenated, filtered and evaporated. To the residue 
were added 2 ml of hydrochloric acid and ethyl acetate so as to 
precipitate crystals which were then filtered off and washed with ethyl 
acetate and petroleum ether. 
The hydrochloride was dissolved in 100 ml of H.sub.2 O and 10 ml of 
hydrochloric acid. The solution was cooled with 50 g of ice and diazotized 
with 7 g of sodium nitrite dissolved in 30 ml of water. The diazonium salt 
solution was added to an ice-cooled solution of 30 g of 2-hydroxyphenyl 
acetic acid in 24 g o sodium hydroxide and 200 ml of water. After 15 
seconds the solution was acidified with hydrochloric acid and extracted 
with ethyl acetate. The ethyl acetate solution was shaken against water, 
dried, treated with active carbon and evaporated. The residue was leached 
with chloroform. The residue then obtained was dissolved in methanol-water 
(about 20%) and treated with active carbon wile hot (about 80.degree. C.). 
More hot water was added until opalescence was obtained, and the solution 
was again treated with active carbon. It was then cooled, and the crystals 
were filtered off and recrystallized from acetonitrile-ethylene 
dichloride. The crystals were dried for 4 hours at 100.degree. C. 
Yield 12 g. Melting point 196.degree. C. (not stage). 
NMR analysis confirmed the structure of the substance. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
C 58.06 58.1 
H 4.33 4.3 
N 7.53 7.5 
______________________________________ 
EXAMPLE 2 
5-(3,5-bis-(methoxycarbonyl)-phenylazo)-2-hydroxy-phenylacetic acid 
20.9 g of dimethyl-5-amino-benzene-1,3-dicarboxylate was dissolved in 20 ml 
of concentrated hydrochloric acid in 200 ml of ice water. The solution was 
diazotized with 7 g of sodium nitrite dissolved in 30 ml of water. 30.4 g 
of 2-hydroxy-phenylacetic acid was dissolved in 200 ml of water and 24 g 
of sodium hydroxide. The solution was cooled with 100 g of ice. To this 
hydroxide solution was then added the diazonium salt solution, all at 
once, and with vigorous stirring. After 30 seconds the solution was 
acidified with acetic acid and the precipitate was filtered off. The 
precipitate was leached with an about 25% ethanol solution which was then 
diluted with water until a state of weak opalescence was reached. The 
solution was treated with active carbon and evaporated down to half its 
volume. Sodium hydrogen carbonate was added until the solution was clear, 
whereupon the solution was heated (80.degree. C.) and acidified with 
hydrochloric acid. The solution was cooled, the crystals were filtered off 
and dried. 
Yield 24 g. 
Melting point 232.degree. C. 
NMR analysis confirmed the structure of the substance. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
C 58.06 57.6 
H 4.33 4.2 
N 7.53 7.3 
______________________________________ 
EXAMPLE 3 
5-(3,5-dicarboxy-phenylazo)-2-hydroxy-phenylacetic acid 
12 g of 5-(3,5-bis-(methoxycarbonyl)-phenylazo)-2-hydroxyphenylacetic acid, 
350 ml of water and 7 g of sodium hydroxide were boiled for 1 hour. 50 ml 
of ethanol was added, and the solution was diluted with water to 500 ml. 
The hot solution was acidified with hydrochloric acid to pH 2 and cooled. 
The crystals were filtered off, washed with water and dried. 
Yield 12 g. 
Melting point &gt;260.degree. C. 
NMR analysis confirmed the identity of the substance. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
C 55.82 55.6 
H 3.51 3.4 
N 8.14 7.9 
______________________________________ 
EXAMPLE 4 
5-(3,4-dicarboxy-phenylazo)-2-hydroxy-phenylacetec acid 
6 g of 5-(3,4-bis-methoxycarbonyl)-phenylazo)-2-hydroxyphenylacetic acid 
and 3.9 g of sodium hydroxide dissolved in 100 ml of water were boiled for 
45 minutes. The solution was acidified with hydrochloric acid and cooled, 
the crystals were filtered off and washed with water. They were dried for 
4 hours at 100.degree. C. 
Yield: 5.3 g. 
Melting point 208.degree. C. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
C 55.82 55.9 
H 3.51 3.7 
N 8.14 7.8 
______________________________________ 
EXAMPLE 5 
5-(3,4-bis-(ethoxycarbonyl)-phenylazo)-2-hydroxy-phenylacetic acid 
27 g of diethyl-5-nitro-benzene-1,3-dicarboxylate was dissolved in 400 ml 
of acetic acid, and 1 g of 10% palladium on carbon, suspended in 10 ml of 
hydrochloric acid, was added. The suspension was hydrogenated, filtered 
and evaporated. The residue was leached with ethyl acetate and dried. The 
hydrochloride was suspended in 150 ml of water, 50 ml of tetrahydrofuran, 
10 ml of hydrochloric acid, and was cooled with 50 g of ice. It was 
diazotized with 7 g of sodium nitrite dissolved in 30 ml of water. The 
diazonium salt solution was poured onto an ice-cooled solution of 30 g 
2-hydroxy-phenylacetic acid and 24 g sodium hydroxide in 200 ml of water. 
The solution was acidified after 15 seconds with acetic acid and extracted 
with chloroform. The chloroformic phase was dried, treated with active 
carbon and evaporated. The evaporation residue was leached gently with 
chloroform, the residue then being dissolved in 300 ml of ethanol. 250 ml 
of hot water was added, and the solution was treated with active carbon. 
The solution was cooled to 30.degree. C. and the product was filtered off 
and dried for 4 hours in vacuo at 100.degree. C. 
Yield 19 g. 
Melting point 198.degree. C. (melting point bench). 
NMR analysis confirmed the structure of the substance. 
______________________________________ 
Elemental analysis: 
Calculated 
Found 
______________________________________ 
C 59.99 60.1 
H 5.03 5.1 
N 7.00 6.6 
______________________________________ 
EXAMPLE 6 
The biological effect of compounds according to the present invention is 
illustrated by the following experiments: 
The compound of Example 2 was studied in respect of its inhibitory effect 
on human PGDH isolated from placenta. 
Radioactively labelled prostaglandin PGF 2 was incubated with the enzyme as 
according to Berry, C. N. et al., Biochem. Pharmacol. 1983, Vol. 32, p. 
2863. 
The compound of Example 2 was added in various concentrations, and the 
inhibition was measured as stated above. 
The compound showed a 50% PGDH inhibition at a concentration of 28 nM. When 
similarly tested against PGDH from rat colon the compound gave 50% PGDH 
inhibition at 56 nM. For comparison, it may be mentioned that the known 
substances IV and V 
##STR5## 
produced 50% inhibition of human PGDH at concentrations of 12 000 nM 
(compound IV) and 290 nM (compound V) respectively. It should be noted 
that (V) is the strongest inhibitor of this type known in the literature. 
No inhibition whatever of cyclooxygenase could be detected at 
concentrations of from 10 to 1,000 nM.