PHENOXYETHYL DIHYDRO-1H-ISOOUINOLINE COMPOUNDS
The present invention relates to novel phenoxyethyl dihydro-lH-isoquinoline
compounds, to pharmaceutical compositions comprising the compounds, to methods of
using the compounds to treat physiological disorders, and to intermediates and processes
useful in the synthesis of the compounds.
The present invention is in the field of treatment of inflammatory conditions, sucl
as arthritis, including osteoarthritis and rheumatoid arthritis, and further including pain
associated with these conditions. Arthritis affects millions of people in the United States
alone and is a leading cause of disability. In addition, arthritis is recognized as a
significant cause of disability in companion animals. Treatments often include NSAIDs
(nonsteroidal anti-inflammatory drugs) or COX-2 inhibitors, which may produce
untoward cardiovascular and/or gastrointestinal side effects in patients. As such, certain
patients may be precluded from using NSAIDs or COX-2 inhibitors. Thus, there is a
need for an alternative treatment of osteoarthritis and rheumatoid arthritis, preferably
without the side effects of the current treatments.
Four prostaglandin E2 (PGE2) receptor subtypes have been identified as the
following: EPl, EP2, EP3 and EP4. It has been disclosed that EP4 is the primary receptc
involved in joint inflammatory pain in rodent models of rheumatoid arthritis and
osteoarthritis. Hence, a selective EP4 antagonist may be useful in treating arthritis,
including arthritic pain. In addition, it has been suggested that since EP4 antagonism
does not interfere with biosynthesis of prostanoids, such as PGI2 and TxA2, a selective
EP4 antagonist may not possess the potential cardiovascular side effects seen with
NSAIDs and COX-2 inhibitors.
WO 2013/004290 discloses cyclic amine derivatives as EP4 receptor antagonists.
US 2005/0250818 discloses certain ortho substituted aryl and heteroaryl amide
compounds that are EP4 receptor selective antagonists with analgesic activity. In
addition, WO 2011/102149 discloses certain compounds that are selective EP4
antagonists which are useful in treating IL-23 mediated diseases.
The present invention provides certain novel compounds that are selective
inhibitors of EP4 relative to EPl, EP2, and EP3. In addition, the present invention
provides certain novel compounds with the potential for reduced cardiovascular or
gastrointestinal side effects in comparison to traditional NSAIDs.
Accordingly, the pres a I :
wherein R is H or F;
or a pharmaceutically acceptable salt thereof.
The present invention also provides a method of treating arthritis in a patient,
comprising administering to a patient in need of such treatment an effective amount of a
compound of Formula I, or a pharmaceutically acceptable salt thereof. The present
invention further provides a method of treating osteoarthritis in a patient, comprising
administering to a patient in need of such treatment an effective amount of a compound of
Formula I, or a pharmaceutically acceptable salt thereof. In addition, the present
invention provides a method of treating rheumatoid arthritis in a patient, comprising
administering to a patient in need of such treatment an effective amount of a compound of
Formula I, or a pharmaceutically acceptable salt thereof. The present invention also
provides a method of treating pain associated with arthritis in a patient, comprising
administering to a patient in need of such treatment an effective amount of a compound of
Formula I, or a pharmaceutically acceptable salt thereof. The present invention further
provides a method of treating pain associated with osteoarthritis or rheumatoid arthritis in
a patient, comprising administering to a patient in need of such treatment an effective
amount of a compound of Formula I, or a pharmaceutically acceptable salt thereof.
Furthermore, the invention provides a compound of Formula I or a
pharmaceutically acceptable salt thereof for use in therapy, in particular for the treatment
of osteoarthritis. In addition, the invention provides a compound of Formula I or a
pharmaceutically acceptable salt thereof for use in the treatment of rheumatoid arthritis.
The invention also provides a compound of Formula I, or pharmaceutically acceptable
salt thereof for use in the treatment of pain associated with osteoarthritis or rheumatoid
arthritis. Furthermore, the invention provides the use of a compound of Formula I, or a
pharmaceutically acceptable salt thereof, for the manufacture of a medicament for the
treatment of osteoarthritis. The invention provides the use of a compound of Formula I,
or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for the
treatment of rheumatoid arthritis. The present invention also provides the use of a
compound of Formula I, or a pharmaceutically acceptable salt thereof, for the
manufacture of a medicament for the treatment of pain associated with osteoarthritis or
rheumatoid arthritis.
The invention further provides a pharmaceutical composition comprising a
compound of Formula I, or a pharmaceutically acceptable salt thereof, with one or more
pharmaceutically acceptable carriers, diluents, or excipients. In a particular embodiment,
the composition further comprises one or more other therapeutic agents. The invention
also provides a pharmaceutical composition for treating arthritis comprising the
compound of Formula I, or a pharmaceutically acceptable salt thereof. This invention
also encompasses novel intermediates and processes for the synthesis of the compound of
Formula I, or a pharmaceutically acceptable salt thereof.
As used herein, the terms "treating" or "to treat" includes restraining, slowing,
stopping, or reversing the progression or severity of an existing symptom or disorder.
As used herein, the term "patient" refers to a mammal which includes a human, a
companion animal, such as a cat or a dog, or a livestock animal, such as a horse, cow, or
pig. Humans and companion animals are preferred patients.
As used herein, the term "effective amount" refers to the amount or dose of the
compound of the invention, or a pharmaceutically acceptable salt thereof which, upon
single or multiple dose administration to the patient, provides the desired effect in the
patient under diagnosis or treatment.
An effective amount can be readily determined by the attending diagnostician, as
one skilled in the art, by the use of known techniques and by observing results obtained
under analogous circumstances. In determining the effective amount for a patient, a
number of factors are considered by the attending diagnostician, including, but not limited
to: the species of mammal; its size, age, and general health; the specific disease or
disorder involved; the degree of or involvement or the severity of the disease or disorder;
the response of the individual patient; the particular compound administered; the mode of
administration; the bioavailability characteristics of the preparation administered; the
dose regimen selected; the use of concomitant medication; and other relevant
circumstances.
The compounds of the present invention are generally effective over a wide
dosage range. For example, dosages per day normally fall within the range of about 0.01
to about 50 mg/kg of body weight. In some instances dosage levels below the lower limit
of the aforesaid range may be more than adequate, while in other cases still larger doses
may be employed with acceptable side effects, and therefore the above dosage range is
not intended to limit the scope of the invention in any way.
The compounds of the invention are preferably formulated as pharmaceutical
compositions administered by any route which makes the compound bioavailable. Most
preferably, such compositions are for oral administration. Such pharmaceutical
compositions and processes for preparing same are well known in the art. (See, for
example, Remington: The Science and Practice of Pharmacy (D.B. Troy, Editor, 21st
Edition, Lippincott, Williams & Wilkins, 2006).
The compounds of the presention invention are particularly useful in the treatment
methods of the invention, but certain groups, substituents, and configurations are
preferred. The following paragraphs describe such preferred groups, substituents, and
configurations. It will be understood that these preferences are applicable both to the
treatment methods and to the new compounds of the invention.
The compound of Formula la:
or pharmaceutically acceptable salt thereof, is preferred.
In addition, the compound of Formula lb:
or pharmaceutically acceptable salt thereof, is preferred.
An especially preferred compound is 4-[(15')-l-[[(3/?)-2-(2-phenoxyethyl)-3,4-
dihydro-lH-isoquinoline-3-carbonyl]amino]ethyl]benzoic acid, which is:
or a pharmaceutically acceptable salt thereof.
4-[(15')-l-[[(3«)-2-(2-Phenoxyethyl)-3,4-dihydro-lH-isoquinoline-3-
carbonyl]amino]ethyl]benzoic acid is most preferred.
Certain stereochemical centers have been left unspecified and certain substituents
have been eliminated in the following schemes for the sake of clarity and are not intended
to limit the teaching of the schemes in any way. Furthermore, individual isomers,
enantiomers, or diastereomers may be separated or resolved by one of ordinary skill in the
art at any convenient point in the synthesis of compounds of Formula I by methods such
as selective crystallization techniques, or chiral chromatography (See for example, J .
Jacques, et al., "Enantiomers, Racemates, and Resolutions" , John Wiley and Sons, Inc.,
1981, and E.L. Eliel and S.H. Wilen," Stereochemistry of Organic Compounds", Wiley-
Interscience, 1994). Alternatively, suitable and readily available chiral starting materials
may also be utilized as appreciated by one of ordinary skill in the art. Additionally,
intermediates described in the following schemes contain nitrogen protecting groups. The
protection and deprotection conditions are well known to the skilled artisan and are
described in the literature (See for example "Greene's Protective Groups in Organic
Synthesis", Fourth Edition, by Peter G.M. Wuts and Theodora W. Greene, John Wiley
and Sons, Inc. 2007).
As used herein, "kPag" refers to kilopascals gauge; "Pg" refers to a suitable
protecting group; "DMEM" refers to Dulbecco's Modified Eagle's Medium; "Boc"
refers to a r -butoxy carbonyl protecting group; "DMSO" refers to dimethylsulfoxide;
"THF' refers to tetrahydrofuran; "EtOAc" refers to ethyl acetate; "Et20 " refers to
diethyl ether; "TBME" refers to r -butyl methyl ether; "BOP" refers to benzotriazol-1-
yloxytris(dimethylamino)phosphonium hexafluorophosphate; "PGE2" refers to
prostaglandin E2; "FBS" refers to Fetal Bovine Serum; "IBMX" refers to (3-isobutyl-lmethylxanthine);
"MES" refers to (2-(N-morpholino)ethanesulfonic acid; "HEPES"
refers to (2-[4-(2-hydroxyethyl)piperazin-l-yl]ethanesulfonic acid); "HTRF" refers to
homogeneous time-resolved fluorescence technology; "HEK" refers to human embryonic
kidney; "HBSS" refers to Hank's Balanced Salt Solution ; "EC 0" refers to the
concentration of an agent that produces 80% of the maximal efficacy possible for that
agent; and "IC50" refers to the concentration of an agent that produces 50% of the
maximal inhibitory response possible for that agent.
The compounds of the present invention, or pharmaceutically acceptable salts
thereof, may be prepared by a variety of procedures known in the art, some of which are
illustrated in the schemes, preparations, and examples below. The specific synthetic steps
for each of the routes described may be combined in different ways, or in conjunction
with steps from different schemes, to prepare the compound of Formula I, or
pharmaceutically acceptable salt thereof. The products of each step in the schemes below
can be recovered by conventional methods, including extraction, evaporation,
precipitation, chromatography, filtration, trituration, and crystallization. The reagents and
starting materials are readily available to one of ordinary skill in the art. All substituents,
unless otherwise specified, are as previously defined. It is understood that these schemes,
preparations, and examples are not intended to be limiting to the scope of the invention in
any way.
Scheme 1
(1 )
In Scheme 1, step A, a protected 3,4-dihydro-lH-isoquinoline-3-carboxylic acid,
wherein Pg is a suitable nitrogen protecting group, such as a a r -butoxy carbonyl
protecting group (BOC), is coupled with methyl 4-(l-aminoethyl)benzoate under standard
conditions to provide the protected isoquinoline amide of structure (1). For example, the
protected 3,4-dihydro-lH-isoquinoline-3-carboxylic acid is dissolved in a suitable organic
solvent, such as dichloromethane, cooled to about 0°C, and treated with about 1.1
equivalents of a suitable organic base, such as triethylamine. Then about 1.1 equivalents
of isobutyl chloroformate are added dropwise with stirring. The mixture is allowed to stir
for about 20 minutes at 0°C, followed by addition of about 1.1 equivalents of the methyl
4-(l-aminoethyl)benzoate. The reaction mixture is then stirred for about 1 hour at room
temperature. The protected isoquinoline amide (1) is then isolated using methods well
known in the art, such as extraction techniques. For example, water is added to the
mixture, the layers are separated, and the organic phase is washed with aqueous
potassium bisulfate, followed by aqueous sodium bicarbonate. The organic phase is then
dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced
pressure to provide the protected isoquinoline amide (1).
Scheme 2
(2) or HCI salt of (2)
In Scheme 2, step A, the protected isoquinoline amide (1) is deprotected under
conditions well known in the art to provide the deprotected isoquinoline amide (2). For
example, about 10 equivalents of acetyl chloride is added dropwise to about 11
equivalents of ethanol dissolved in a suitable organic solvent, such as ethyl acetate at
about 0°C. The mixture is stirred for about 30 minutes, warmed to room temperature and
then a solution of about 1 equivalent of the protected isoquinoline amide (1) in ethyl
acetate is added to the reaction mixture with stirring. The reaction mixture is then stirred
at about 40°C for about 12 hours. It is then cooled to room temperature and the
deprotected isoquinoline is isolated using techniques well known in the art. For example,
the solid is collected by filtration and dried under reduced pressure. Water is added to the
solid followed by addition of 32% aqueous ammonia until the pH of the mixture reaches
about 10. The solids are again collected by filtration and dried under reduced pressure at
about 45°C to provide the deprotected isoquinoline amide (2).
Alternatively, in Scheme 2, step A, the protected isoquinoline amide (1) can be
deprotected under conditions well known in the art to provide the HCI salt of the
deprotected isoquinoline amide (2). For example, the protected isoquinoline amide (1) is
dissolved in a 4 M solution of hydrogen chloride in 1,4-dioxane. The reaction is stirred
for abour 12 hours at room temperature. The HC1 salt of the deprotected isoquinoline
amide (2) is then isolated by concentrating the reaction mixture under reduced pressure.
In Scheme 2, step B, the deprotected isoquinoline amide (2) is coupled with a
suitably substituted phenoxy compound to provide the phenoxyethyl isoquinoline (3).
For example, silica gel is combined with a suitable organic solvent, such as
dichloromethane at about 22°C ,and a solution of about 2 equivalents of sodium periodate
in water is added dropwise to the stirring silica gel mixture. The mixture is stirred for
about 30 minutes, and about 1.5 equivalents of 3-phenoxy- 1,2-propanediol is added. The
mixture is stirred for about another 30 minutes, then filtered to remove solids, the layers
are separated, and the organic layer is dried over magnesium sulfate. The organic layer is
again filtered and about 1 equivalent of the deprotected isoquinoline amide (2) is added
followed by about 2 equivalents of a suitable reducing agent, such as sodium
triacetoxyborohydride in portions. The reaction mixture is then allowed to stir for about
one hour followed by addition of excess water. An aqueous solution of 32% ammonia is
added to the mixture until the pH of the aqueous layer reaches about 10.
The phenoxyethyl isoquinoline (3) is then isolated and purified by techniques well
know in the art. For example, the layers of the reaction mixture are separated, the organic
layer is dried over magnesium sulfate, filtered, and concentrated under reduced pressure.
The crude oil is dissolved in a suitable organic solvent, such as TBME, water is added,
followed by 1M aqueous HC1. The resulting slurry is stirred for about 30 minutes and
then concentrated under reduced pressure to remove the organic solvent. The precipitate
is then collected by filtration and added to a mixture of water and TBME. The mixture is
treated with 32% aqueous ammonia under the pH of the aqueous layer reaches about 10,
the layers are separated, and the organic layer is washed with saturated aqueous sodium
chloride, dried over magnesium sulfate, filtered, and concentrated under reduced pressure.
The resulting crude material is purified by flash chromatography on silica gel with a
suitable eluent, such as ethyl acetate/hexanes to provide the purified phenoxyethyl
isoquinoline (3).
Alternatively, in Scheme 2, step B, the HC1 salt of the deprotected isoquinoline
amide (2) can coupled with a suitably substituted phenoxy compound to provide the
phenoxyethyl isoquinoline (3). For example, about 1.5 equivalents of a 2-
phenoxyacetaldehyde, such as 2(4-fluorophenoxy)acetaldehyde, is combined with about 1
equivalent of the HC1 salt of the deprotected isoquinoline amide (2) in a suitable organic
solvent, such as 1,2-dichloroethane. To this mixture is added about 1.4 equivalents of a
suitable reducing agent, such as sodium triacetoxyborohydride and the reaction mixture is
stirred for about 12 hours at room temperature. Saturated aqueous sodium bicarbonate is
then added to the reaction mixture and the phenoxyethyl isoquinoline (3) is isolated and
purified by techniques well know in the art. For example, the reaction mixture is
extracted with a suitable organic solvent, such as ethyl acetate, the organic extracts are
combined, washed with saturated aqueous sodium chloride, dried over magnesium
sulfate, filtered, and concentrated under reduced pressure. The crude material is then
purified by flash chromatography on silica gel with a suitable eluent, such as ethyl
acetate/hexanes to provide the purified phenoxyethyl isoquinoline (3).
Scheme 3
In Scheme 3, step A, the phenoxyethyl isoquinoline (3) is hydrolyzed under
conditions well known in the art to provide the compound of Formula I . For example, the
phenoxyethyl isoquinoline (3) is dissolved in a suitable organic solvent, such as THF, or a
mixture of methanol/THF, and then treated with about 2 to 4 equivalents of a suitable
aqueous base, such as aqueous sodium hydroxide. The reaction is then stirred at a
temperature of about 20°C to about 40°C for about 12 hours. The compound of Formula
I is then isolated and purified under conditions well known in the art. For example, the
reaction mixture is concentrated under reduced pressure to remove the organic solvent.
Water is added and the aqueous layer is washed with a suitable organic solvent, such as
TBME. The aqueous layer is then cooled to about 5°C and treated with a suitable
aqueous acid, such as hydrochloric acid, with stirring, until the pH reaches about 2. The
reaction is then warmed to room temperature and the solids collected by filtration. The
solids are then added to water, heated to about 80°C for about one hour, cooled to room
temperature, collected by filtration, and dried under reduced pressure at about 45°C for
abour 12 hours. The dried solid is then added to a suitable organic solvent, such as
isopropyl acetate and stirred for about 5 hours. The solids are collected by filtration and
dried under reduced pressure to provide the purified compound of Formula I .
Pharmaceutically acceptable salts and common methodology for preparing them
are well known in the art. See, for example, Gould, P.L., "Salt selection for basic drugs,"
International Journal of Pharmaceutics, 33: 201-217 (1986); Bastin, R.J., et al. "Salt
Selection and Optimization Procedures for Pharmaceutical New Chemical Entities,"
Organic Process Research and Development, 4 : 427-435 (2000); and Berge, S.M., et al.,
"Pharmaceutical Salts," Journal of Pharmaceutical Sciences, 66: 1-19, (1977). One
skilled in the art of synthesis will appreciate that the compounds of the present invention
may be converted to and may be isolated as a pharmaceutically acceptable salt using
techniques and conditions well known to one of ordinary skill in the art.
Preparations and Examples
The following preparations and examples further illustrate the invention. Unless
noted to the contrary, the compounds illustrated herein are named and numbered using
Accelrys Draw (IUPAC name).
Preparation 1
Synthesis of r -butyl (3/?)-3-[[(15')-l-(4-methoxycarbonylphenyl)ethyl]carbamoyl]-3,4-
dihydro- lH-isoquinoline-2-carboxylate.
Scheme 1, Step A: To a 0 °C mixture of (3R)-2-tert-butoxycarbonyl-3,4-dihydrolH-
isoquinoline-3-carboxylic acid (40.0 g, 141 .4 mmol) and dichloromethane (784 mL),
add triethylamine (21.7 mL, 155.5 mmol). Then add isobutyl chloroformate (20.3 mL,
155.5 mmol) in a dropwise fashion. After the end of the addition, stir the mixture at 0 °C
for 20 minutes. Then, add methyl (5)-4-(l-aminoethyl)benzoate (27.9 g, 155.5 mmol),
and stir the mixture at room temperature for 1 hour. Add water (400 mL), separate the
layers, and wash the organic layer with 1M aqueous KHSO4 (500 mL), followed by
saturated aqueous NaHCC>3 (500 mL). Dry the organic phase over MgS0 4, filter to
remove the solids, and concentrate the filtrate under reduced pressure to furnish the title
compound as a white solid (60 g, 97% yield). Mass spectrum (m/z): 339 ([M + H -
Boc] +), 383 ([M + H - i-Bu] +), 439 ([M + H]+) .
Preparation 2
Synthesis of methyl 4-[(15)-l-[[(3/?)-l,2,3,4-tetrahydroisoquinoline-3-
carbonyl]amino]ethyl]benzoate.
Scheme 2, Step A: Cool a mixture of ethyl acetate (214 mL) and ethanol (87.6
mL, 1.51 mol) to 0 °C, and then add acetyl chloride (97.4 mL, 1.37 mol) in a dropwise
fashion. Stir the mixture for 30 minutes while allowing it to warm to room temperature.
Add a solution of r -butyl (3R)-3-[[(15)-l-(4-
methoxycarbonylphenyl)ethyl]carbamoyl]-3,4-dihydro-lH-isoquinoline-2-carboxylate
(60 g, 137 mmol) in ethyl acetate (480 mL), and then stir the resulting mixture at 40 °C
overnight. Cool the mixture to room temperature, then isolate the resulting precipitate by
filtration, and dry under reduced pressure. Add water (300 mL) to the solid, and then add
a 32% aqueous ammonia solution until the pH of the mixture reaches 10. Isolate the
suspended solids by filtration, then dry them in a vacuum oven at 45 °C overnight to
furnish the title compound as a white solid (44 g, 95% yield). Mass spectrum (m/z): 339
([M + H]+), 677 ([2M + H]+), 699 ([2M + Na]+) .
Preparation 3
Synthesis of methyl 4-[(15')-l-[[(3«)-2-(2-phenoxyethyl)-3,4-dihydro-lH-isoquinoline-3-
carbonyl]amino]ethyl]benzoate.
Scheme 2, Step B: To a stirring mixture of silica gel (200 g, 3.33 mol) and
dichloromethane (1100 mL) at 22 °C, add a solution of sodium periodate (56.2 g, 260
mmol) in water (352 mL) in a dropwise fashion. After the end of the addition, stir the
mixture for an additional 30 minutes, then add 3-phenoxyl-l,2-propanediol (34.5 g, 195
mmol), resulting in a slight exotherm. Stir the mixture for an additional 30 minutes, then
filter to remove the solids, discard the aqueous layer, and dry the organic layer over
MgS0 4, filter to remove the solids, and treat the filtrate with methyl 4-[(lS)-l-[[(3fl)-
l,2,3,4-tetrahydroisoquinoline-3-carbonyl]amino]ethyl]benzoate (44 g, 130 mmol).
Then, add sodium triacetoxyborohydride (57.4 g, 260 mmol) in small portions. Upon
completion of the addition, stir the mixture for one additional hour, then add water (200
mL). Add a 32% aqueous ammonia solution until the pH of the aqueous layer reaches 10.
Separate the layers, dry the organic layer over MgS0 4, filter to remove the solids, and
concentrate the filtrate under reduced pressure. Dissolve the resulting crude oil in TBME
(300 mL), then add water (250 mL) and 1M aqueous hydrochloric acid (200 mL). Stir
the resulting slurry for 30 minutes, concentrate under reduced pressure to remove the
TBME, and isolate the resulting white precipitate by filtration. Pour this precipitate into a
stirring mixture of water (400 mL) and TBME (400 mL), and add a 32% aqueous
ammonia solution until the pH of the aqueous layer reaches 10. Remove the aqueous
layer, and wash the organic layer with a saturated aqueous sodium chloride solution (200
mL). Isolate the organic layer, dry over MgS0 4, filter to remove the solids, and
concentrate under reduced pressure. Subject the resulting crude material to flash
chromatography on silica gel using a 30% to 70% EtOAc/hexanes gradient. Consolidate
the fractions containing the product, and concentrate them under reduced pressure to
furnish the title compound as a white solid (44 g, 74% yield). Mass spectrum (m/z): 459
([M + H]+) .
Preparation 4
Synthesis of methyl 4-[(15)-l-[[(3/?)-l,2,3,4-tetrahydroisoquinoline-3-
carbonyl]amino]ethyl]benzoate hydrochloride.
Scheme 2, step A: Dissolve tert-butyl (3fl)-3-[[(lS)-l-(4-
methoxycarbonylphenyl)ethyl]carbamoyl]-3,4-dihydro-lH-isoquinoline-2-carboxylate
(5.5 g, 12.5 mmol) in a 4 M solution of hydrogen chloride in 1,4-dioxane (30 mL, 120
mmol). Stir the mixture overnight at room temperature, and then concentrate the mixture
under reduced pressure to furnish the title compound as a white solid (4.70 g, 100%
yield). Mass spectrum (m/z): 339 ([M + H]+), 677 ([2M + H]+), 699 ([2M + Na]+) .
Preparation 5
Synthesis of methyl 4-[(15)- l-[[(3/?)-2-(2-(4-fluorophenoxy)ethyl)-3,4-dihydro-lHisoquinoline-
3-carbonyl]amino]ethyl]benzoate.
Scheme 2, Step B: To a mixture of methyl 4-[(15)- l-[[(3 R)- l,2,3,4-
tetrahydroisoquinoline-3-carbonyl]amino]ethyl]benzoate hydrochloride (800 mg, 2.13
mmol) and 2-(4-fluorophenoxy)acetaldehyde (493 mg, 3.2 mmol) in 1,2-dichloroethane
(10.7 mL), add sodium triacetoxyborohydride (633 mg, 2.99 mmol) and stir the mixture
at room temperature overnight. Add saturated aqueous NaHCC>3 (25 mL), and extract the
aqueous layer with ethyl acetate (2 x 25 mL). Wash the combined organic layers with
saturated aqueous NaCl (25 mL), dry the organic phase over MgS0 4, filter, and
concentrate the filtrate under reduced pressure. Subject the resulting crude material to
flash chromatography on silica gel using a 0% to 60% EtOAc/hexanes gradient.
Consolidate the fractions containing the product, and concentrate them under reduced
pressure to furnish the title compound as a colorless foam (550 mg, 54% yield). Mass
spectrum (m/z): 477 ([M + H]+) .
Example 1
Synthesis of 4-[(15')-l-[[(3«)-2-(2-phenoxyethyl)-3,4-dihydro- lH-isoquinoline-3-
carbonyl]amino]ethyl]benzoic acid.
Scheme 3, Step A: Stir a mixture of methyl 4-[(15)- l-[[(3/?)-2-(2-phenoxyethyl)-
3,4-dihydro- lH-isoquinoline-3-carbonyl]amino]ethyl]benzoate (41 .5 g, 90.5 mmol), THF
(291 mL), and 2 M aqueous sodium hydroxide (18 1 mL, 360 mmol) at 40 °C overnight.
Concentrate under reduced pressure to remove the THF. Add water (200 mL), then wash
the aqueous layer with TBME (2 x 200 mL). Cool the aqueous layer to 5 °C and add
concentrated aqueous hydrochloric acid with stirring until the pH reaches 2 (as estimated
by pH paper analysis). With stirring, allow the mixture to warm to room temperature
over 30 minutes, then isolate the solids by filtration. Add the solids to water (500 mL)
and heat to 80 °C for one hour. Cool the mixture to room temperature, isolate the solids
by filtration, and dry the solids in a vacuum oven at 45 °C overnight. Add the solids to
isopropyl acetate (300 mL) and stir vigourously for 5 h. Isolate the solids by filtration,
and dry the solids under reduced pressure to furnish the title compound as a white solid
(26 g, 60% yield). Mass spectrum (m/z): 445 ([M + H]+) .
Example 2
Synthesis of 4-[(15')-l-[[(3«)-2-(2-(4-fluorophenoxy)ethyl)-3,4-dihydro-lH-isoquinoline-
3-carbonyl]amino]ethyl]benzoic acid hydrochloride.
Scheme 3, Step A: Dissolve methyl 4-[(lS)-l-[[(3 R)-2-(2-(4-
fluorophenoxy)ethyl)-3,4-dihydro-lH-isoquinoline-3-carbonyl]amino]ethyl]benzoate
(550 mg, 1.15 mmol) in a mixture of methanol (10 mL) and tetrahydrofuran (10 mL).
Add a 5 N aqueous solution of sodium hydroxide (0.462 mL, 2.31 mmol), then stir the
mixture at room temperature overnight. Concentrate the mixture under reduced pressure
to furnish a white solid. Add a 4 M solution of hydrogen chloride in 1,4-dioxane (10 mL,
40 mmol), and stir the mixture at room temperature for 10 min. Remove the suspended
solids by filtration, rinsing the solids with THF (5 mL). Concentrate the combine filtrate
under reduced pressure to furnish a white solid. Triturate the material in hot diethyl ether
(10 mL), and filter to furnish the title compound as a white solid (535 mg, 93% yield).
Mass spectrum m/ z) 463 ([M + H]+), 485 ([M + Na]+) .
n Vitro binding to human EP1, EP2, EP3 and EP4
hEPl and hEP4 membranes are prepared from recombinant HEK293 cells stably
expressing the human EP1 (Genbank accession number AY275470) or EP4 (Genbank
accession number AY429109) receptors. hEP2 and hEP3 membranes are prepared from
HEK293 cells transiently transfected with EP2 (Genbank accession number AY275471)
or EP3 (isoform VI: Genbank accession number AY429108) receptor plasmids. Frozen
cell pellets are homogenized in homogenization buffer using a Teflon/glass homogenizer.
Membrane protein is aliquoted and quick frozen on dry ice prior to storage at -80 °C.
Homogenization buffer (see e.g., Mauback, K.A., British Journal of Pharmacology, 156:
316-327 (2009)) contained 10 mM Tris-HCl, pH 7.4, 250 mM sucrose, 1mM EDTA, 0.3
mM indomethacin and plus Complete™, with EDTA, obtained from Roche Molecular
Biochemicals (Catalog Number 1 697 498).
Kd values for [3H]-PGE2 binding to each receptor are determined by saturation
binding studies or homologous competition. Compounds are tested in a 96-well format
using a three-fold dilution series to generate a 10-point curve. Diluted compound is
incubated with 20 EP2, 1 ug/well EP3 or 10 to 20 EP4
membrane for 90 minutes at 25 C in the presence of 0.3 to 0.5 nM [ H]-PGE2
(PerkinElmer, 118 to 180 Ci/mmol). The binding reaction is performed in 200 E MES
buffer (10 mM MES pH 6.0 with KOH, 10 mM MgCl2 and 1mM EDTA) using 0.5 mL
polystyrene 96-well deep-well plates. Nonspecific binding is calculated by comparing
binding in the presence and absence of 2 mM of PGE2. The membranes are harvested by
filtration (TomTek harvester), washed 4 times with cold buffer (lOmM MES pH 6.0 with
KOH, 10 mM MgCl2), dried in a 60 °C oven, and the radioactivity is quantified as counts
per minute (CPM) using a TopCount® detector. Percent specific binding is calculated as
the percent of the binding in the absence of any inhibitor, corrected for non-specific
binding in the presence of 2 mM of PGE2. Data are analyzed using a 4-parameter
nonlinear logistic equation (ABase Equation 205) as shown: y = (A+((BA)/(
l+((C/x) D)))) where, y = % specific inhibition, A = bottom of the curve; B = top of
the curve; C = relative IC50 = concentration causing 50% inhibition based on the range of
the data from top to bottom; D = Hill Slope = slope of the curve. K\ conversion from IC50
Values {K\ =IC5o/(l + [L]A¾) where [L] is the ligand concentration).
Table 1: In vitro binding of Examples 1 and 2 to human EP1, EP2, EP3 and EP4
Test hEPl, i (nM) hEP2, i (nM) hEP3, i (nM) hEP4, i (nM)
Compound
Ex. 1 7920±5810(n=3) 1320±1780(n=4) >14800 (n=3) 0.403±0.247(n=9)
Ex. 2 4650 (n=l) 331±72(n=2) >14600 (n=l) 0.380±0.142(n=4)
The compounds are tested following the procedures essentially as described
above. The data in Table 1 demonstrate that the compounds of Example 1 and Example 2
bind to hEP4 at sub-nanomolar concentrations. The data in Table 1 also demonstrate the
compounds of Example 1 and Example 2 bind to hEP4 more strongly than to hEPl,
hEP2, and hEP3 indicating selectivity for the hEP4 receptor.
In Vitro human EP4 functional antagonist activity
Assays are conducted in recombinant HEK293 cells stably expressing human EP4
receptor. The cell lines are maintained by culturing in DMEM with high glucose and
pyridoxine hydrochloride (Invitrogen) supplemented with 10% fetal bovine serum (FBS),
1 mM sodium pyruvate, 10 mM HEPES, 500 mg/mL geneticin and 2 mM L-glutamine.
Confluent cultures are grown at 37 °C in an atmosphere containing 5% C0 2. Cells are
harvested using 0.25% Trypsin-EDTA, suspended in freeze media (FBS with 6% DMSO)
at 107 cells/mL and aliquots are stored in liquid nitrogen. Just before assay, cells are
thawed in DMEM, centrifuged, and resuspended in cAMP buffer.
The inhibition of PGE2-stimulated cAMP production by EP4 antagonists is
measured using HTRF (Cisbio catalogue # 62AM4PEB). An aliquot equivalent to 4000
cells is incubated with 50 E cAMP assay buffer containing PGE2 in a concentration
predetermined to produce an ECso (0.188nM PGE2 from Sigma, catalog # P5640-10mg)
and EP4 antagonists at room temperature for 20 minutes. cAMP assay buffer contains
500 mL HBSS, 0.1 % BSA, 20 mM HEPES and 200 mM IBMX (Sigma 15879). CJ-
042794 serves as a positive control (see WO 2005/021508, example 68, 4-{(lS)-l-[({5-
chloro-2-[(4-fluorophenyl)oxy]phenyl} carbonyl)amino]ethyl}benzoic acid; see also
Murase, A., et al., Life Sciences, 82:226-232 (2008)). To measure the cAMP levels,
cAMP-d2 conjugate and anti cAMP-cryptate conjugate in lysis buffer are incubated with
the treated cells at room temperature for 1 hour. The HTRF signal is detected using an
EnVision® plate reader (Perkin-Elmer) to calculate the ratio of fluorescence at 665 nm to
that at 620 nm. The raw data are converted to cAMP amount (pmol/well) using a cAMP
standard curve generated for each experiment. Data are analyzed using a 4-parameter
nonlinear logistic equation (ABase Equation 205) as shown: y = (A+((BA)/(
l+((C/x) D)))) where, y = % specific inhibition, A = Bottom of the curve, B = Top of
the curve, C = Relative IC50 = concentration causing 50% inhibition based on the range of
the data from top to bottom, D = Hill, Slope = slope of the curve.
The compounds are tested following the procedures essentially as described
above. The compound of Example 1 has an IC50 of 0.752+0.538 nM (n=12) and the
compound of Example 2 has an IC50 of 0.450+0.256 nM (n=4) measured at human EP4.
This demonstrates that the compounds of Example 1 and Example 2 are antagonists of
human EP4 in vitro.
In Vitro rat EP4 functional antagonist activity
Rat EP4 cDNA (Genebank Accession* NM_03276) is cloned into pcDNA 3.1
vector and subsequently transfected in HEK293 cells for receptor expression. Rat EP4
stable clone is scaled up and then frozen down as cell bank for future compounds
screening. To test EP4 antagonist compounds in rEP4 cells, thaw the frozen cells and
then resuspend cells in cAMP assay buffer. The cAMP buffer is made by HBSS without
Phenol Red (Hyclone, SH30268) supplemented with 20 mM HEPES (Hyclone,
SH30237), 0.1% BSA (Gibco, 15260) and 125 mM IBMX (Sigma, 15879) (see e.g.,
Murase, A., et al., Life Sciences, 82:226-232 (2008)). The cells are plated into 96-well
half area flat-bottom polystyrene black plates (Costar 3694). Compounds are serial
diluted with DMSO to give 10-point concentration response curves. Then diluted
compounds are added into cAMP assay buffer which contains PGE2 (Cayman 14010, in a
concentration predetermined to produce an ECso) at ratio of DMSO/buffer at 1/100. The
cells are treated with compounds in the presence of PGE2 (ECso concentration) for 30
minutes at room temperature. The cAMP levels generated from the cells are quantified
by a cAMP HTRF assay kit (Cisbio 62AM4PEC). The plates are read on an EnVision
plate reader using HTRF optimized protocol (PerkinElmer). IC50S are calculated using
Graphpad Prism (v. 4) nonlinear regression, sigmoidal dose response curve fitting.
The compounds are tested following the procedures essentially as described
above. The compound of Example 1 has an IC50 of 2.0 nM (n=l) and the compound of
Example 2 has an IC50 of 6.7 nM (n=l) measured at rat EP4. This demonstrates that the
compounds of Example 1 and Example 2 are antagonists of rat EP4 in vitro.
In Vitro antagonist activity in human whole blood
The inhibitory effects of PGE2 on LPS-induced TNFa production from
macrophages/monocytes are believed to be mediated by EP4 receptors (See Murase, A.,
et al., Life Sciences, 82:226-232 (2008)). The ability of the compound of Example 1 to
reverse the inhibitory effect of PGE2 on LPS-induced TNFa production in human whole
blood is an indicia of functional activity.
Blood is collected from normal volunteer donors into sodium heparin vacutainer
tubes. Donors have not taken NSAIDs or celecoxib within 48 hours or glucocorticoids
within two weeks prior to the donation. All tubes/donor are pooled into 50 mL Falcon
conical centrifuge tubes and 98 mE/well is distributed into 96-well tissue culture plates
(Falcon 3072). Compounds are diluted into DMSO to 100 X final and 1 in
triplicate is added to the blood to give 7-point concentration response curves. The blood
is pretreated with the compounds at 37 °C, in a 5% C0 2 humidified atmosphere, for 30
minutes, after which 1 mE/well of a solution of 1 mg/mL of lipopolysaccharide (LPS)
(Sigma 0111:B4) in 0.2 mg/mL bovine serum albumin (BSA)/PBS both with and without
1mM PGE2 (Cayman 14010) is added to give a final LPS concentration of 10 mg/mL
both with and without 10 nM PGE2. The plates are incubated for 20-24 hours at 37 °C in
a 5% C0 2, humidified atmosphere. The plates are centrifuged at 1800 x g for 10 minutes
at 22 °C, in an Eppendorf 5810R centrifuge. Plasma is removed from the cell layer and is
transferred to v-bottom polypropylene plates. TNFa levels in 2 m plasma are quantified
by a commercially available enzyme immunoassay (R&D Systems DY210), using
Immulon 4 HBX plates (Thermo 3855) and 3,3', 5,5' tetramethylbiphenyl-4,4'-diamine
substrate (KPL 50-76-03). The plates are read at A450-A650 on a plate reader (Molecular
Devices Versamax) using SOFTmaxPRO (v. 4.3.1) software. IC50S are calculated using
Graphpad Prism (v. 4) nonlinear regression, with sigmoidal dose response curve fitting.
Results are expressed as the geometric mean + standard deviation; n = number of
independent determinations.
The compounds are tested following the procedures essentially as described
above. The compound of Example 1 has an IC50 of 39+21nM (n=8) and Example 2 has
an IC50 of 61+55nM (n=5) measured at human EP4. This demonstrates that the
compounds of Example 1 and Example 2 are EP4 antagonists in the human blood TNFa
induction assay.

I CLAIM:
1. A compound of the formula:
wherein R is H or F;
or a pharmaceutically acceptable salt thereof.
The compound or salt according to claim 1 which
3. The compound or salt according to either claim 1 or claim 2 which is:
4. The compound according to claim 3 which is 4-[(lS)-l-[[(3R)-2-(2-
phenoxyethyl)-3,4-dihydro-lH-isoquinoline-3-
carbonyl]amino]ethyl]benzoic acid:
or a pharmaceutically acceptable salt thereof.
5. The compound according to claim 4 which is 4-[(15)-1-[[(3/?)-2-(2-
phenoxyethyl)-3,4-dihydro-lH-isoquinoline-3-
carbonyl]amino]ethyl]benzoic acid:
6. The compound according to claim 3 which is 4-[(15')-l-[[(3/?)-2-(2-(4-
fluorophenoxy)ethyl)-3 ,4-dihydro- lH-isoquinoline-3-
carbonyl]amino]ethyl]benzoic acid:
or a pharmaceutically acceptable salt thereof.
A method of treating osteoarthritis in a patient, comprising administering
to a patient in need of such treatment an effective amount of a compound,
or pharmaceutically acceptable salt thereof, according to claim 1.
8. A method of treating rheumatoid arthritis in a patient, comprising
administering to a patient in need of such treatment an effective amount of
a compound, or pharmaceutically acceptable salt thereof, according to
claim 1.
9. A method of treating pain associated with osteoarthritis or rheumatoid
arthritis in a patient, comprising administering to a patient in need of such
treatment an effective amount of a compound, or a pharmaceutically
acceptable salt thereof, according to claim 1.
10. A compound or pharmaceutically acceptable salt thereof according to
claims 1 to 6 for use in therapy.
A compound or pharmaceutically acceptable salt thereof according to
claims 1 to 6 for use in the treatment of osteoarthritis.
A compound or pharmaceutically acceptable salt thereof according to
claims 1 to 6 for use in the treatment of rheumatoid arthritis.
A compound or pharmaceutically acceptable salt thereof according to
claims 1 to 6 for use in the treatment of pain associated with osteoarthritis
or rheumatoid arthritis.
14. A pharmaceutical composition, comprising a compound or a
pharmaceutically acceptable salt thereof according to claims 1 to 6 with
one or more pharmaceutically acceptable carriers, diluents, or excipients.