SUBSTITUTED 3-BENZOFURANYL-INDOL-2-ONE-3-
ACETAMIDOPIPERAZINE DERIVATIVES, PREPARATION THEREOF, AND
THERAPEUTIC USE THEREOF
The present invention relates to substituted 3-benzofuranyl-indol-2-one-3-
acetamidopiperazine derivatives, to their preparation and to their therapeutic
application.
Ghrelin is a 28 amino-acid peptide hormone produced mainly in the stomach
by a post-translational process after cleavage of pre-pro-ghrelin (Kojima M.,
et al., Nature 1999; 402: 656-60). Ghrelin is an endogenous ligand of the
growth hormone secretagogue pituitary receptor (GHSR1a).
GHS-R is encoded by two exons: exon 1 encodes the transmembrane
domains (TMs) 1-5 and exon 2 encodes TM6 and 7 of the G-protein-coupled
receptor (GPCR).
The two transcripts have been identified in the pituitary gland and the brain:
one encoding the full-length GPCR (GHS-R1a) and the other encoding a
truncated receptor (GHS-R1b) lacking TM6 and 7. Only the subtype GHS-
RIa is activated by ghrelin and ghrelin mimetics. GHS-R1b is present in the
liver and other peripheral tissues, but its function is unknown (Smith R.G. et
al., Trends in Endocrinology and Metabolism, 2005, 16, No. 9).
It is a receptor of rhodopsin type, with seven transmembrane domains of
family A coupled to Gq/phospholipase C. The ghrelin receptor may also be
coupled to the Gs/protein kinase A pathways in certain tissues (Ueno, N. et
al., Endocrinology, 2004, 145, 4176-4184; Kim, M.S. et al., Int. J. Obes. Relat.
Metab. Disord., 2004, 28: 1264-1271). Interestingly, the ghrelin receptor has
the relatively uncommon characteristic of having significant ligand-
independent constitutive activity (Barazzoni, R. et al., Am. J. Physiol.
Endocrinol. Metab., 2004, 288: E228-E235).
Low levels of expression of ghrelin have been documented in various tissues,
such as the intestines, the pancreas, the kidneys, the immune system, the
placenta, the testicles, pituitary tissue and the hypothalamus (Horm. Res.
2003; 59(3): 109-17).
It has been demonstrated that ghrelin is involved in hunger at mealtimes, and
in the initiation of meals. The circulating levels decreases with the intake of
food and increase after meals, reaching concentrations that are sufficient to
stimulate hunger and the intake of food. Ingestion of ghrelin stimulates food
intake rapidly and transiently, mainly by increasing the appetitive feeding
behaviour and the number of meals. Ghrelin stimulates the short-term taking
of food more efficiently than any other molecule, with the exception of
neuropeptide Y, with which it is approximately equipotent (Wren A.M. et al., J.
Clin. Endocrinol. Metab., 2001; 86: 5992-5). However, ghrelin is unique in its
capacity to exert this effect, whether it is injected peripherally or centrally.
It is also the only mammalian substance that has demonstrated its capacity to
increase the appetite and the taking of food when it is administered to
humans (Druce M.R., et al., Int. J. Obes., 2005; 29: 1130-6; Wynne K., et al.,
J. Am. Soc. Nephrol., 2005; 16: 2111-8).
Beyond its role in the initiation of meals, ghrelin also satisfies the established
criteria of an adiposity-related hormone involved in regulating the long-term
body mass. The levels of ghrelin circulate as a function of the energy
reserves and display compensatory changes in response to changes in body
mass.
Ghrelin crosses the blood-brain barrier and stimulates the taking of food by
acting on certain standard body mass-regulating centres, such as the
hypothalamus, the hindbrain and the mesolimbic compensatory system.
Chronic administration of ghrelin increases the body mass via diverse
concerted actions on the taking of food, energy expenditure and the utilisation
of resources. Congenital ablation of ghrelin or of the ghrelin receptor gene
causes a resistance to feeding-induced obesity, and pharmacological
blocking of ghrelin reduces the intake of food and the body mass.
The existing evidence appears to favour the role of ghrelin both in the short-
term initiation of meals and long-term energy homeostasis, thus making it an
attractive target as a medicament for treating obesity and/or slimming
disorders.
Ghrelin also exerts both physiological and pharmacological actions on the
endocrine pancreas. Acylated bioactive ghrelin is produced in the s cells,
recently described in the pancreatic islets (Prado, C.L., et al., 2004, Proc. Natl
Acad. Sci. USA, 101: 2924-2929), potentially providing a local source of
ghrelin that acts on the p cells of the islets. Blockage of this function of
endogenous ghrelin by means of an antagbnist for its receptors substantially
reduced the fasted glucose concentrations, attenuated the glycaemic
movement and increased the responses to insulin during glucose tolerance
tests, suggesting an inhibitory role of ghrelin in the control of insulin secretion
(Dezaki, K., et al. 2004, Diabetes, 53: 3142-3151).
Ablation of ghrelin in mice (ghrelin -/- mice) increases the glucose-dependent
secretion of insulin by the p cells of the pancreas, by reducing the Ucp2
expression and increases the sensitivity to peripheral insulin (Sun Y. et al.,
2006, Cell Metabolism, 3: 379-386).
Ghrelin receptor antagonists could thus regulate hunger, the taking of meals
and their frequency, and also, in the long-term, the weight, especially weight
gain following diets or therapeutic regimens. Furthermore, in the context of an
antidiabetic treatment, ghrelin antagonists could be useful for maintaining the
equilibrium between insulin and glucose for controlling diabetic hyperphagia.
Ghrelin antagonists could thus be used as anorexic and/or anti-obesity
agents, or alternatively in the treatment of diabetes and its effects.
One subject of the present invention is compounds corresponding to formula
(I):

in which:
R1 represents a hydrogen atom or a (C1-6)alkyl, -C(=O)(C1-6)alkyl or
-C(=O)aryl group;
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, CN, OH, a (C1-6)alkyl group optionally substituted with
a halogen atom or an OH; perhalo(C1-3)alkyl, (C1-6)alkoxy, perhalo(C1-
3)alkoxy, aminocarbonyl, (C1-6)alkylaminocarbonyl, di(C1-6)alkylamino-
carbonyl, aryl, aryloxy; heteroaryl; the aryl, aryloxy or heteroaryl group
possibly being optionally substituted with a halogen atom, CN, OH or a (C1-
6)alkyl, perhalo(C1-3)alkyl or (C1-6)alkoxy group; it being understood that at
least one from among R2, R3 and R4 is other than H and that the aryl,
aryloxy or heteroaryl group may be optionally substituted with a halogen
atom, CN, OH or a (C1-6)alkyl, perhalo(C1-3)alkyl or (C1-6)alkoxy group;
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl or R5 and R6 together form a C3-C6 ring;
R7 represents a group (C1-C6)alkyl or a group (C2-6)alkenyl;
R8 and R9, which are located on any of the available positions of the
piperazine nucleus, represent a hydrogen atom, a group (C1-C6)alkyl or a
group (C2-6)alkenyl, it being understood that at least one from among R8 and
R9 is other than H;
or two from among R7, R8 and R9 together form a C3-C6 ring;
it being understood that R8 and R9 may be in the geminal position on the
same carbon atom;
n represents 1 or 2.
The compounds of formula (I) comprise one or more asymmetric carbon
atoms. They may thus exist in the form of enantiomers or diastereoisomers.
These enantiomers and diastereoisomers, and also mixtures thereof,
including racemic mixtures, form part of the invention.
The compounds of formula (I) may exist in the form of bases or of acid-
addition salts. Such addition salts form part of the invention.
These salts may be prepared with pharmaceutically acceptable acids, but the
salts of other acids that are useful, for example, for purifying or isolating the
compounds of formula (I) also form part of the invention.
In the context of the present invention, the following definitions apply:
- a halogen atom: a fluorine, a chlorine, a bromine or an iodine;
- an alkyl group: a linear or branched saturated aliphatic group. Examples that
may be mentioned include a (C1-6)alkyl group containing from 1 to 6 carbon
atoms, more particularly (C1-4)alkyl, which may represent a methyl, ethyl,
propyl, isopropyl, butyl, isobutyl or tert-butyl;
- an alkenyl group: a linear or branched, monounsaturated or polyunsaturated
aliphatic group comprising, for example, one or two unsaturations and
containing from 2 to 6 carbon atoms;
- a haloalkyl group: an alkyl group in which one or more hydrogen atoms have
been replaced with a halogen atom; for example a fiuoroalkyl: an alkyl group
in which one or more hydrogen atoms have been replaced with a fluorine
atom;
- a perhaloalkyl group: an alkyl group in which all the hydrogen atoms have
been replaced with a halogen atom; for example, a perfluoroalkyl: an alkyl
group in which all the hydrogen atoms have been replaced with a fluorine
atom;
- an alkoxy group: a radical -O-alkyl in which the alkyl group is as defined
above;
- a perhaloalkoxy group: a radical -O-perhaloalkyl in which the perhaloalkyl
group is as defined above; mention may be made, for example, of
trifluoromethoxy;
- an aryl group: a cyclic aromatic group containing between 6 and 10 carbon
atoms. Examples of aryl groups that may be mentioned include phenyl and
naphthyl;
- a heteroaryl group: a cyclic aromatic group containing between 2 and 10
carbon atoms and comprising between 1 and 3 heteroatoms, such as
nitrogen, oxygen or sulfur. Examples of heteroaryl groups that may be
mentioned include furyl, pyrrolyl, imidazolyl, pyrazolyl, thienyl, oxadiazolyl,
oxazolyl, isoxazolyl, furazanyl, thiadiazolyl, thiazolyl, isothiazolyl, pyridyl,
pyrazinyl, pyrimidinyl and pyridazinyl groups, and also the corresponding
groups resulting from fusion with a phenyl group, for instance
benzothiophene, benzofuran, benzothiazole, etc.
Among the compounds of formula (I) that are subjects of the invention, one
group of compounds is constituted by the compounds for which:
R1 represents a hydrogen atom or a (C1-6)alkyl, -C(=O)(C1-6)alkyl or
-C(=O)aryl group;
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, CN, OH or a (C1-6)alkyl, perhalo(C1-3)alkyl, (C1-
6)alkoxy, perhalo(C1-3)alkoxy, aminocarbonyl, (C1-6)alkylaminocarbonyl,
di(C1-6)alkylaminocarbonyl, aryl, aryloxy or heteroaryl group, it being
understood that at least one from among R2, R3 and R4 is other than H;
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl or R5 and R6 together form a C3-C6 ring;
R7 represents a group (C1-C6)alkyl;
R8 and R9, which are located on any of the available positions of the
piperazine nucleus, represent a hydrogen atom, a group (C1-C6)alkyl, it being
understood that at least one from among R8 and R9 is other than H;
or two from among R7, R8 and R9 together form a C3-C6 ring;
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
Among the compounds of formula (I) that are subjects of the invention, one
group of compounds is constituted by the compounds for which:
R1 represents a hydrogen atom or a -C(=O)(C1-6)alkyl, -C(=O)aryl or (C1-
6)alkyl group; and/or
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, more particularly chlorine or bromine, or a (C1-6)alkyl
or trifluoromethyl group, it being understood that at least one from among R2,
R3 and R4 is other than H; and/or
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl; and/or
R7 represents a group (C1-C6)alkyl; and/or
R8 and R9, which are located on positions 2 and 6 of the piperazine nucleus,
represent a hydrogen atom, a group (C1-C6)alkyl, it being understood that at
least one from among R8 and R9 is other than H; and/or
two from among R7, R8 and R9 together form a C3-C6 ring; and/or
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
Among the compounds of formula (I) that are subjects of the invention,
another group of compounds is constituted by the compounds for which:
R1 represents a hydrogen atom or a -C(=O)methyl, -C(=O)phenyl or methyl
group; and/or
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, more particularly chlorine or bromine, or a methyl or
trifluoromethyl group, it being understood that at least one from among R2,
R3 and R4 is other than H; and/or
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl; and/or
R7 represents a methyl or ethyl group; and/or
R8 and R9, which are located on positions 2 and 6 of the piperazine nucleus,
represent a hydrogen atom or a methyl or ethyl group, it being understood
that at least one from among R8 and R9 is other than H; and/or
two from among R7, R8 and R9 together form a C3-C6 ring; and/or
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
Among the compounds of formula (I) that are subjects of the invention,
mention may be made especially of the following compounds:
Compound No. 1: (+)-N-[4,6-dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-
1H-indol-3-yl]-2-(4-ethyl-3,5-dimethylpiperazin-1-yl)acetamide;
Compound No. 2: (+)-N-[4,6-dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-
1H-indol-3-yl]-2-(4-ethylpiperazin-1-yl)propionamide;
in the form of the base or of an acid-addition salt.
In the text hereinbelow, the term "protecting group Pg" means a group that
makes it possible firstly to protect a reactive function such as a hydroxyl or an
amine during a synthesis, and, secondly, to regenerate the intact reactive
function at the end of the synthesis. Examples of protecting groups and of
protection and deprotection methods are given in Protective Groups in
Organic Synthesis, Greene et al., 2nd edition (John Wiley & Sons, Inc., New
York).
In the text hereinbelow, the term "leaving group" means a group that may be
readily cleaved from a molecule by breaking a heterolytic bond, with loss of
an electron pair. This group may thus be readily replaced with another group
during a substitution reaction, for example. Such leaving groups are, for
example, halogens or an activated hydroxyl group such as a
methanesulfonate, benzenesulfonate, p-toluenesulfonate, triflate, acetate, etc.
group. Examples of leaving groups and references for their preparation are
given in Advances in Organic Chemistry, J. March, 3rd edition, Wiley
Interscience, pp. 310-316.
In accordance with the invention, the compounds of general formula (I) may
be prepared according to the process that follows:
The compound of formula (I), in which R1 is other than H and R2, R3, R4, R5,
R6, R7, R8, R9 and n are as defined in the general formula (I), may be
prepared by reacting a compound of formula (I) in which R1 = H with a
compound of formula (II):
R1-Hal(ll)
in which R1, which is other than H, is defined as in the general formula (I) and
Hal represents a halogen atom, for example chlorine, according to methods
known to those skilled in the art, for example in the presence of a base such
as K2CO3, NaH or t-BuO-K+, in a solvent such as dimethylformamide (DMF),
tetrahydrofuran (THF), dimethoxyethane or dimethyl sulfoxide (DMSO).
The compound of general formula (I) may be prepared according to one or
other of the following variants:
The compound of general formula (I) in which R1 = H may be prepared
according to the following method, from a compound of general formula (V):

and from a compound of general formula (VII):

in which R2, R3, R4, R5, R6, R7, R8, R9 and n are as defined in the general
formula (I). This reaction is generally performed using a halogenating agent,
such as a chlorinating agent, for example phosphorus chlorides, especially
PCI5, or alternatively PCI3 or POCI3. The reaction is generally performed in
the presence of pyridine or 4-dimethylaminopyridine, in a solvent such as
dichloromethane or DMF.
The compound of general formula (I) in which R1, R5 and R6 = H may be
prepared according to the following method, by reacting a compound of
general formula (III):

with a compound of general formula (IV):

in which R2, R3, R4, R7, R8, R9 and n are as defined in the general formula
(I) and Hal" represents a halogen atom, preferably chlorine. This reaction is
generally performed using an organic or mineral base, such as K2CO3,
Na2CO3, pyridine or 4-dimethylaminopyridine, in the presence of Nal or Kl, in
an inert solvent such as DMF, dichloromethane, THF, dimethoxyethane or
toluene.
The compound of general formula (III) may be prepared from a compound of
general formula (V):

and from a compound of general formula (VI):

in which R2, R3 and R4 are as defined in the general formula (I) and Hal' and
Hal", which may be identical or different, independently represent a halogen
atom, preferably chlorine.
This reaction is generally performed using pyridine or 4-
dimethylaminopyridine in a solvent such as toluene, benzene or
dichloromethane, preferentially at a temperature of between room
temperature and the reflux point of the solvent.
Room temperature is meant to be a temperature of between 5 and 25°C.
The intermediates of general formula (V) are known and may be prepared
according to the processes illustrated by scheme that follows:
Scheme 2:

in which R2, R3 and R4 are as defined in the general formula (I) and Hal
represents a halogen atom, for example chlorine.
In step c of Scheme 2, the compound of formula (V) is prepared from a
compound of formula (VIII) by sparging with ammonia gas according to the
method described in patent application FR 2 714 378.
It is also possible to prepare the same compound via reduction of a
compound of formula (X) according to methods known to those skilled in the
art, for example by means of zinc in a solvent such as methanol. The
preparation of a compound of formula (X) of the step is described in patent
application FR 2 714 378.
An optically pure compound of formula (V) may be synthesized according to
steps d and e of Scheme 2, as described in patent application WO
03/008407.
The intermediates of general formula (VIII) may be prepared according to the
processes described in patent application WO 03/008407 and illustrated by
Scheme 3:
Scheme 3:

in which R2, R3 and R4 are as defined in the general formula (I) and Hal
represents a halogen atom, for example chlorine.
The compound of general formula (VII) may be prepared according to the
following methods, illustrated by Schemes 4 and 5:
Scheme 4:

The compound of general formula (XIII) may be prepared by condensation of
a compound of general formula (IV):

in which R7, R8, R9 and n are defined as in the general formula (I), with a
corresponding halo compound, such as Har"CH2COOAIk, in which Hal'"
represents a halogen atom such as chlorine and Alk represents an alkyl
group, such as ethyl. This reaction is advantageously performed in a solvent
such as toluene, benzene or dioxane.

The compound of general formula (XIII) may be prepared by condensation of
a compound of general formula (XIV):

in which R5, R6, R8, R9 and n are defined as in the general formula (I) and
Alk represents an alkyl group, with a compound R7-Hal"' in which Hal"'
represents a halogen atom, such as chlorine, and R7 is defined as in the
general formula (I). This reaction is advantageously performed in a solvent
such as toluene, benzene, dioxane or DMF in the presence of a base such as
triethylamine or potassium carbonate.
According to another embodiment, the compounds of general formula (I) in
which R1 represents an alkyl group and R2, R3, R4, R5, R6, R7, R8, R9 and
n are as defined in the general formula (I) may also be prepared according to
Scheme 6 below:

According to this scheme, a compound of formula (V) is reacted with a
protecting group PG to give the compound of formula (XV). Examples of
protecting groups PG for the amine that may be used include benzimine and
t-butyl carbamate. These protecting groups are introduced according to
methods known to those skilled in the art, for example in the presence of a
base such as K2CO3, NaOH or triethylamine, in a solvent such as dioxane,
THF or DMSO.
The compound of general formula (XVI) may be prepared by reacting a
compound of formula (XV) with a compound of formula ALK-Hal in which ALK
represents a linear or branched saturated aliphatic group containing from 1 to
6 carbon atoms and Hal represents a halogen atom, for example chlorine.
The compound of general formula (XVII) is obtained from a compound of
formula (XVI) by removing the protecting group according to well-known
methods, for example in acidic medium with HCI or trifluoroacetic acid.
The compound of formula (XVII) obtained is then reacted with a compound of
general formula (VII):

in which R2, R3, R4, R5, R6, R7, R8, R9 and n are as defined in the general
formula (I). This reaction is generally performed using a halogenating agent,
such as a chlorinating agent, for example phosphorus chlorides, especially
PCI5 or PCI3 or POCI3. The reaction is generally performed in the presence of
pyridine or 4-dimethylaminopyridine, in a solvent such as dichloromethane or
DMF.
Optionally, the compound of formula (I) is converted into an acid-addition salt
thereof.
The process according to the invention may optionally include the step that
consists in isolating the desired product of general formula (I).
In Schemes 1, 2, 3, 4, 5 and 6, the starting materials and the reagents, when
their mode of preparation is not described, are commercially available or
described in the literature, or else may be prepared according to methods that
are described therein or that are known to those skilled in the art.
The examples that follow describe the preparation of certain compounds in
accordance with the invention. These examples are not limiting, and serve
merely to illustrate the present invention.
The physicochemical measurements were performed in the following manner:
The melting points were measured using a Buchi B-540 machine.
The proton nuclear magnetic resonance (1H NMR) spectra were recorded at
500 MHz on a Bruker machine equipped with an Avance console. The
chemical shifts are given in pprn relative to the frequency of TMS.
All the spectra were recorded at a temperature of 40°C.
The abbreviations used to characterized the signals are as follows:
s = singlet, bs = broad singlet, m = multiplet, bm = broad multiplet,
d = doublet, bd =.broad doublet, t = triplet, q = quartet.
* = not integratable due to interference with a broad peak resulting from
water.
** = not integratable due to interference with a peak resulting from the NMR
solvent.
*** = read at first order.
**** = the most abundant diastereoisomer.
***** = the least abundant diastereoisomer.
The analysis conditions by liquid chromatography coupled to mass
spectrometry (LC/UV/MS) are as follows:
For the liquid chromatography part:
XTerra MS C18 3.5 urn column
- chromatographic system:
- Eluent A = H2O + 0.01% TFA
- Eluent B = CH3CN
- gradient from 98% A to 95% B over 10 minutes, followed by elution with
95% B for 5 minutes
- flow rate 0.5 ml/minute
- injection of 2 uL of solution at 0.1 mg/ml in a 9/1 CH3CN/H2O mixture
The products are detected by UV at 220 nm.
For the mass spectrometry part:
- ionization mode: positive electrospray (API-ES polarity+)
- scanning from 100 to 1200 amu.
Thin layer chromatography was performed on silica gel TLC plates from
Merck. The silica gel for the flash column chromatography is sold by Biotage.
All the solvents used are of "reagent grade" or "HPLC grade" purity.
The aD measurements were recorded on a Perkin-Elmer model PE341
polarimeter using a cell with a 1 dm optical path length.
In the examples and preparations:
AcOH and EtOAc represent, respectively, acetic acid and ethyl acetate.
MeOH, EtOH and t-BuOH represent, respectively, methanol, ethanol and tert-
butanol.
THF represents tetrahydrofuran.
m.p. means melting point.
Preparation 1:
2-(4-Ethylpiperazin-1 -yl)propionic acid
(i) Ethyl 2-(4-ethylpiperazin-1-yl)propionate
9.7 g of ethyl 2-piperazin-1-ylpropionate are placed in 150 ml of DMF and
21.6 g of potassium carbonate in a round-bottomed flask. A solution of 3.9 ml
of bromoethane is added dropwise. The mixture is reacted at 130°C for three
hours, the carbonate is filtered off and the filtrate is concentrated to dryness.
The residue is taken up in ethyl acetate and filtered. The solid is removed and
the liquid phase is evaporated under vacuum. A solid that crystallizes from
ethyl acetate is obtained. It is filtered off to give 8.46 g of the title product.
TLC: 100% MeOH, Rf = 0.55
(ii) 2-(4-Ethylpiperazin-1-yl)propionic acid
8.45 g of the product obtained in the preceding step are added to 180 ml of
6N HCI and the mixture is reacted for 4 hours at reflux. The resulting mixture
is evaporated to dryness, the residue is washed with a 1/1 EtOAc/EtOH
mixture and the white solid obtained is dried. 5.4 g of expected product are
obtained.
TLC: 100% MeOH, Rf = 0.2
Preparation 2:
(+)-3-Amino-4,6-dichloro-1,3-dihydro-3-(benzofuran-5-yl)indoIe-2-one
(i)3-Hydroxy-4,6-dichloro-1,3-dihydro-3-(benzofuran-5-yl)indole-2-one
2.25 g of magnesium for a Grignard reaction in 15 ml of anhydrous THF are
placed in a round-bottomed flask equipped with a mechanical stirrer, and
under a stream of nitrogen. A mixture of 13.6 g of 5-bromobenzofuran in
35 ml of anhydrous THF is then added. The mixture is stirred for one hour,
followed by addition of a solution of 5 g of 4,6-dichloro-1H-indole-2,3-dione in
50 ml of anhydrous THF. The mixture is stirred at room temperature for
4 hours 30 minutes. Water is added and the resulting mixture is extracted with
ethyl acetate. The organic phase is separated out, dried over Na2SO4, filtered
and evaporated under vacuum. The residue is taken up in ethyl acetate and
washed with 1N sodium hydroxide solution. The organic phase is dried over
Na2SO4, filtered and evaporated under vacuum. The solid is taken up in ethyl
ether and filtered off. 4.2 g of expected product are obtained.
(ii)3,4,6-Trichloro-1,3-dihydro-3-(benzofuran-5-yl)indole-2-one
4.1 g of the product from the preceding step are placed in 40 ml of
dichloromethane in a round-bottomed flask equipped with a magnetic stirrer,
and under a stream of nitrogen. At 0°C, 1.7 ml of pyridine and a mixture of
1.4 ml of SOCI2 in 30 ml of dichloromethane are added. The resulting mixture
is reacted at room temperature and then poured into saturated aqueous
NH4CI solution. The organic phase is separated out, dried over Na2SO4,
filtered and evaporated under vacuum.
TLC: 7/3 hexane/EtOAc, Rf = 0.65
(iii) 4,6-Dichloro-[[(1 S)-2-hydroxy-1 -phenylethyl]amino]-1,3-dihydro-3-
(benzofuran-5-yl)indole-2-one isomer A and isomer B
4.1 g of the compound from the preceding step in 50 ml of dichloromethane
and 3.1 g of S-phenylglycinol are mixed together under a stream of nitrogen.
The mixture is left to react overnight at room temperature. The solid formed is
filtered off and the filtration liquors are evaporated to dryness and purified on
a column, eluting with 8/2 hexane/EtOAc.
0.64 g of less polar product, isomer A (m.p. = 135°C) and 1.23 g of the more
polar isomer B are obtained.
(v) (+)-3-Amino-5,6-dichloro-1,3-dihydro-3-(4-chlorophenyl)indole-2-one
1.21 g of the product obtained in the preceding step in a mixture of 20 ml of
dichloromethane and 15 ml of methanol are reacted. 1.26 g of Pb(OAc)4 are
added and the mixture is reacted at room temperature for 1 hour. The
resulting mixture is evaporated to dryness and the residue is taken up in ethyl
acetate and then washed with saturated aqueous NaHCO3 solution. The
organic phase is dried, filtered and concentrated. The residue is taken up in a
mixture of 36 ml of 3N hydrochloric acid and 3.7 ml of methanol, and stirred
overnight. The resulting mixture is concentrated and the residue is diluted
with a mixture of water and dichloromethane. The organic phase is washed
with 1N hydrochloric acid solution. The aqueous phases are combined,
brought to basic pH with aqueous NH3 solution and extracted with
dichloromethane. The organic phase is dried, filtered and concentrated to
give 870 mg of solid white product,
m.p. =215-216°C
LC/MS: (M+H)+ = m/z 333 amu; rt = 5.3 minutes
Example 1
(+)-N-[4,6-Dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-1H-indol-3-yl]-
2-(4-ethyl-3,5-dimethylpiperazin-1-yl)acetamide
(i) 2-Chloro-N-[4,6-dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-1H-indol-
3-yl]acetamide:
0.43 g of the product obtained in Preparation 2, 15 ml of toluene, 0.11 ml of
pyridine and 0.11 ml of chloroacetyl chloride are placed in a round-bottomed
flask equipped with a magnetic stirrer, and under a stream of nitrogen. The
mixture is reacted at 110°C for 4 hours and the reaction mixture is then
poured into water and extracted with ethyl acetate. The organic phase is dried
over Na2SO4, filtered and evaporated under vacuum. 500 mg of a beige-
coloured solid are obtained, which product is purified on a column by flash
chromatography using an 8/2 cyclohexane/ethyl acetate mixture to obtain
330 mg of the expected product.
TLC: 1/1 hexane/EtOAc, Rf = 0.5
(ii)(+)-N-[4,6-Dichloro-3-(benzofuran-2-yl)-2-oxo-2,3-dihydro-1H-indol-3-yl]-2-
(3,5-dimethyl-4-ethylpiperazin-1-yl)acetamide:
0.31 g of the product from the preceding step, 0.08 ml of 2,6-dimethyl-N-
ethylpiperazine (d 0.899), 0.1 g of potassium carbonate and 0.05 g of sodium
iodide in 5 ml of DMF are placed in a round-bottomed flask equipped with a
magnetic stirrer. The mixture is reacted at 60°C for 4 hours and the reaction
mixture is then poured into water and extracted with ethyl acetate. The
organic phase is dried over Na2SO4, filtered and evaporated under vacuum.
The title product is obtained.
m.p. = 157-160°C; [aD] = +191°, c = 0, 946 wt% MeOH;
LC/MS: (M+H)+ = m/z 515 amu; rt = 4.9 minutes
Example 2
(+)-N-[4,6-Dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-1H-indol-3-yI]-
2-(4-ethylpiperazin-1-yl)propionamide
1) Under a stream of nitrogen, 520 mg of PCI5 are placed in 12 ml of
anhydrous dichloromethane cooled in an ice bath, followed by slow addition
of 430 mg of the acid of Preparation 1. The reaction mixture is left to act at
0°C for 10 minutes and then at room temperature for 3 hours.
2) Separately, 300 mg of the product from Preparation 2 is suspended in 12
ml of dichloromethane under a stream of nitrogen, followed by addition of
0.3 ml of pyridine. The mixture is cooled in an ice bath. The solution prepared
in 1) is added dropwise and the mixture is stirred at room temperature for one
hour.
The reaction mixture is poured into water and extracted with ethyl acetate.
The organic phase is washed with saturated NaHCO3 solution, dried over
Na2SO4, filtered and evaporated under vacuum. 500 mg of an orange-
coloured solid are obtained, which product is purified on a column by flash
chromatography using 1/1 ethyl acetate/methanol as eluent, to obtain the title
product,
m.p. = 137-138°C; [aD] = +217°, c = 0.1064 wt% in MeOH;
NMR: d (ppm, DMSO-d6): 0.99 (m, 3H), 1.08 (m, 3H), 2.24-2.45 (m, 6H) 2.47-
2.68 (m, **), 3.18-3.33 (m, *), 6.92 (m, 1H), 7.01 (s, 1H), 7.19 (m, 1H), 7.21-
7.28 (m, 1H), 7.50 (bs, 1H), 7.65 (d, J=8.8Hz, 1H), 8.02 (s, 1H), 8.61 (s,
0.4H*****), 8.73 (s, 0.6H****), 10.64 (s, 0.6H****), 10.71 (s, 0.4H*****).
LC/MS: (M+H)+ = m/z 501 amu; rt = 4.9 minutes
Example 3
(+)-N-[4,6-Dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-1H-indol-3-yl]-
2-(4-ethyl-3-methylpiperazin-1-yl)acetamide
The process is performed as described for Example 1,but using 2-methyl-N-
ethylpiperazine instead of 2,6-dimethyl-N-ethylpiperazine, to give the title
compound.
The compounds according to the invention underwent in vivo studies.
in vivo test
Male Crl CD BR rats (Charles River, Italy) weighing 150-175 g were housed
in a chamber at regulated temperature (22±1°C) and humidity (55±10%) and
with a 12-hour lightness-darkness cycle, for at least 7 days before their use.
Feed and water were available ad libitum. The feed was removed 18 hours
before sacrificing the animals. The rats were sacrificed by cervical dislocation,
and the stomach was removed surgically, opened along the shorter curvature
and placed in a Krebs solution (of composition (mM): 118.4 NaCI; 4.7 KCI; 2.5
CaCI2; 3.7 NaH2PO4; 1.2 MgSO4; 25 NaHCO3; 5.6 glucose). The animals
were cared for and sacrificed according to the Sanofi-Aventis international
code of ethics and the international principles governing the care and
treatment of laboratory animals (EEC Directive 86/609, DJL358, 1,
12 December 1987). Strips of approximately 1 cm (5 mm wide) of gastric
fundus were cut out along the longitudinal axis and suspended in 20 ml of
bath filled with the Krebs solution at 37°C and aerated with a 95% O2-5% CO2
gas mixture. The strips were maintained at a resting load of 1 g and, after
washing, 10 uM of choline (acetylcholine precursor) and 10 uM of
indomethacin (prostaglandin synthetase inhibitor) were added to the medium,
to reduce the spontaneous phasic contractions (Depoortere et al., Eur. J.
Pharmacol. 515, 1-3, 160-168, 2003; Dass et al., Neurosciences 120, 443-
453, 2003). Isotonic contractions were initiated by stimulation with an electric
field. Two platinum wire electrodes were placed at the surface and at the
bottom of the organ bath, and the electric-field stimulation was performed with
a Power Lab stimulator (AD Instruments Pty Ltd, Castle Hill, Australia)
coupled to a multiplex pulse propeller (Ugo Basile, Varese, Italy) (Fukuda et
al., Scand. J. Gastroenterol. 12, 1209-1214, 2004). The supramaximal
stimulation was applied to create maximum contractions (20 Hz, pulse width:
2 milliseconds; 5 volts; batch trains every 2 minutes, 150 mA). Next, the
current was reduced to obtain a submaximal stimulation (50% reduction of the
maximum contractile response). The contractions were recorded by computer
with a data recording and analysis system (Power Lab, Chart 5) connected to
isotonic transducers (Ugo Basile, Varese, Italy) via preamplifiers (Octal Bridge
Amp). After stabilization, concentration-response cumulative curves for
ghrelin (0.1 nM-1 µM) were plotted, with and without incubation (contact time:
30 minutes) of the antagonist molecules. Supramaximal electric-field
stimulation was used for each strip as reference (100%) to classify the
responses per test substance. The agonist concentration producing 50% of
the maximum effect (EC50) was calculated using a four-parameter logistic
model according to Ratkovsky and Reedy (Biometn'cs, 42, 575-582, 1986),
with adjustment by non-linear regression using the Levenberg-Marquard
algorithm in the Everstat software. The pKb values for the antagonists were
calculated according to the Cheng-Prusoff equation (Kenakin et al.,
Competitive Antagonism, Pharmacologic Analysis of Drug-Receptor
Interaction, 3rd edition, 331-373, Philadelphia, New York; Raven: Lippincott,
1997).
The compounds of formula (I) show antagonist activity towards the ghrelin
receptor with IC50 values ranging from 5X10-8M and 1X10-9M.
For example, the compound of Example No. 2 has an IC50 value of 1.2X10-
The compounds of formula (I) demonstrated advantageous pharmacological
properties for the development of a medicament, in particular medicaments
for preventing or treating any pathology in which the ghrelin receptor is
involved.
Thus, according to another of its aspects, a subject of the invention is
medicaments comprising a compound of formula (I) or an addition salt thereof
with a pharmaceutically acceptable acid.
Thus, the compounds according to the invention may be used, for man and
animals, in the treatment or prevention of various ghrelin-dependent
complaints. Thus, the compounds according to the invention may be used as
anorexic agents, for regulating the appetite, the taking of meals and their
frequency, and also, in the long-term, the weight, especially weight gain
following diets or therapeutic regimens. The compounds according to the
invention are thus particularly useful for preventing or treating obesity,
appetite disorders, diabetes, excess weight and/or the effects thereof.
According to another of its aspects, the present invention relates to
pharmaceutical compositions comprising, as active principle, a compound
according to the invention. These pharmaceutical compositions contain an
effective dose of at least one compound according to the invention, or a
pharmaceutically acceptable salt thereof, and also at least one
pharmaceutically acceptable excipient.
The said excipients are chosen, according to the pharmaceutical form and the
desired mode of administration, from the usual excipients known to those
skilled in the art.
In the pharmaceutical compositions of the present invention for oral,
sublingual, subcutaneous, intramuscular, intravenous, topical, local,
intratracheal, intranasal, transdermal or rectal administration, the active
principle of formula (I) above, or the salt thereof, may be administered in unit
administration form, as a mixture with standard pharmaceutical excipients, to
animals and human beings, for the prophylaxis or treatment of the above
disorders or diseases.
The appropriate unit administration forms include oral-route forms such as
tablets, soft or hard gel capsules, powders, granules and oral solutions or
suspensions, sublingual, buccal, intratracheal, intraocular or intranasal
administration forms, forms for administration by inhalation, topical,
transdermal, subcutaneous, intramuscular or intravenous administration
forms, rectal administration forms and implants. For topical application, the
compounds according to the invention may be used in creams, gels,
ointments or lotions.
By way of example, a unit administration form of a compound according to the
invention in tablet form may comprise the following components:

Via the oral route, the dose of active principle administered per day may be
from 0.1 to 100 mg/kg in one or more dosage intakes. Via the parenteral
route, it may be from 0.01 to 10 mg/kg/day
There may be particular cases in which higher or lower dosages are
appropriate; such dosages do not depart from the scope of the invention.
According to the usual practice, the dosage that is appropriate to each patient
is determined by the practitioner according to the mode of administration, and
the weight and response of the said patient.
Possible combinations
The present invention also relates to combinations of one or more
compound(s) according to the invention of general formula (I) with one or
more active ingredient(s).
As active ingredient(s) that is (are) suitable for the said combinations, mention
may be made especially of anti-obesity and antidiabetic agents, and also
rimonabant, metformin or sulfonylureas.
According to another of its aspects, the present invention also relates to a
method for treating the pathologies indicated above, which comprises the
administration to a patient of an effective dose of a compound according to
the invention, or of a pharmaceutically acceptable salt thereof.
According to another of its aspects, the present invention also relates to a
compound of formula (I), or a pharmaceutically acceptable salt thereof, for
treating the pathologies indicated above.
CLAIMS
1. Compound corresponding to formula (I):

in which:
R1 represents a hydrogen atom or a (C1-6)alkyl, -C(=O)(C1-6)alkyi or
-C(=O)aryl group;
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, CN, OH, a (C1-6)alkyl group optionally substituted with
a halogen atom or an OH; perhalo(C1-3)alkyl, (C1-6)alkoxy, perhalo(C1-
3)alkoxy, aminocarbonyl, (C1-6)alkylaminocarbonyl, di(C1-6)alkylamino-
carbonyl, aryl, aryloxy; heteroaryl;
the aryl, aryloxy or heteroaryl group possibly being optionally substituted with
a halogen atom, CN, OH or a (C1-6)alkyl, perhalo(C1-3)alkyl or (C1-6)alkoxy
group; it being understood that at least one from among R2, R3 and R4 is
other than H and that the aryl, aryloxy or heteroaryl group may be optionally
substituted with a halogen atom, CN, OH or a (C1-6)alkyl, perhalo(C1-3)alkyl
or (C1-6)alkoxy group;
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl or R5 and R6 together form a C3-C6 ring;
R7 represents a group (C1-C6)alkyl or a group (C2-6)alkenyl;
R8 and R9, which are located on any of the available positions of the
piperazine nucleus, represent a hydrogen atom, a group (C1-C6)alkyl or a
group (C2-6)alkenyl, it being understood that at least one from among R8 and
R9 is other than H;
or two from among R7, R8 and R9 together form a C3-C6 ring;
it being understood that R8 and R9 may be in the geminal position on the
same carbon atom;
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
2. Compound according to Claim 1, such that, in the general formula (I):
R1 represents a hydrogen atom or a (C1-6)alkyl, -C(=O)(C1-6)alkyl or
-C(=O)aryl group;
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, CN, OH or a (C1-6)alkyl, perhalo(C1-3)alkyl,
(C1-6)alkoxy, perhalo(C1-3)alkoxy, aminocarbonyl, (C1-6)alkylaminocarbonyl,
di(C1-6)alkylaminocarbonyl, aryl, aryloxy or heteroaryl group, it being
understood that at least one from among R2, R3 and R4 is other than H;
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl or R5 and R6 together form a C3-C6 ring;
R7 represents a group (C1-C6)alkyl;
R8 and R9, which are located on any of the available positions of the
piperazine nucleus, represent a hydrogen atom, a group (C1-C6)alkyl, it being
understood that at least one from among R8 and R9 is other than H;
or two from among R7, R8 and R9 together form a C3-C6 ring;
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
3. Compound according to Claim 1 or 2, such that, in the general
formula (I):
R1 represents a hydrogen atom or a -C(=O)(C1-6)alkyl, -C(=O)aryl or (C1-
6)alkyl group;
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, or a (C1-6)alkyl or trifluoromethyl group, it being
understood that at least one from among R2, R3 and R4 is other than H;
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl;
R7 represents a group (C1-C6)alkyl;
R8 and R9, which are located on positions 2 and 6 of the piperazine nucleus,
represent a hydrogen atom, a group (C1-C6)alkyl, it being understood that at
least one from among R8 and R9 is other than H;
or two from among R7, R8 and R9 together form a C3-C6 ring;
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
4. Compound according to any one of the preceding claims, such that, in
the general formula (I):
R1 represents a hydrogen atom or a -C(=O)methyl, -C(=O)phenyl or methyl
group;
R2, R3 and R4, which may be identical or different, located on any of the
available positions of the phenyl nucleus, independently represent a hydrogen
atom, a halogen atom, or a methyl or trifluoromethyl group, it being
understood that at least one from among R2, R3 and R4 is other than H;
R5 and R6, which may be identical or different, represent a hydrogen atom or
a group (C1-6)alkyl;
R7 represents a methyl or ethyl group;
R8 and R9, which are located on positions 2 and 6 of the piperazine nucleus,
represent a hydrogen atom or a methyl or ethyl group, it being understood
that at least one from among R8 and R9 is other than H;
or two from among R7, R8 and R9 together form a C3-C6 ring;
n represents 1 or 2;
in the form of the base or of an acid-addition salt.
5. Compound according to any one of the preceding claims, chosen from
the following compounds:
Compound No. 1: (+)-N-[4,6-dichloro-3-(benzofuran-5-yl)-2-oxo-2,3~dihydro-
1H-indol-3-yl]-2-(4-ethylpiperazin-1-yl)acetamide;
Compound No. 2: (+)-N-[4,6-dichloro-3-(benzofuran-5-yl)-2-oxo-2,3-dihydro-
1H-indol-3-yl]-2-(4-ethylpiperazin-1-yl)propionamide;
in the form of the base or of an acid-addition salt.
6. Process for preparing a compound of formula (I) according to any one
of Claims 1 to 5, characterized in that it comprises a step that consists in
reacting a compound of general formula (V):

in which R2, R3 and R4 are as defined according to any one of Claims 1 to 5.
7. Process according to Claim 6, comprising the steps consisting in:
- reacting the said compound of general formula (V) with a compound of
general formula (VI):

in which Hal' and Hal", which may be identical or different, independently
represent a halogen atom;
- and then in reacting the compound of general formula (III) obtained

with a compound of general formula (IV):

in which R2, R3, R4, R7, R8, R9 and n are defined as in the general formula
(I) and Hal" represents a halogen atom;
- optionally followed by the step that consists in reacting the product of
formula (I) obtained, in which R1 is equal to H, with a compound of formula
(II):

in which R1, which is other than H, is defined as in the general formula (I) and
Hal represents a halogen atom.
8. Process according to Claim 6, comprising the step that consists in
reacting the said compound of general formula (V) with a compound of
general formula (VII):

in which R5, R6, R7, R8, R9 and n are as defined according to any one of
Claims 1 to 5;
optionally followed by the step that consists in reacting the product of formula
(I) obtained, in which R1 is equal to H, with a compound of formula (II):
R1-Hal (II)
in which R1, which is other than H, is defined as in the general formula (I) and
Hal represents a halogen atom.
9. Process for preparing a compound of formula (I) according to any one
of Claims 1 to 5, characterized in that it comprises a step that consists in
reacting a compound of general formula (XVII):

in which R2, R3 and R4 are defined according to any one of Claims 1 to 5
and ALK represents an alkyl group.
10. Process according to Claim 9, comprising the step that consists in:
- reacting the said compound of general formula (XVII) with a compound of
general formula (VII):

in which R5, R6, R7, R8, R9 and n are as defined in general formula (I).
11. Process according to any one of Claims 6 to 10, comprising the
subsequent step that consists in separating out the desired compound of
general formula (I).
12. Medicament, characterized in that it comprises a compound of formula
(I) according to any one of Claims 1 to 5, or an addition salt of this compound
with a pharmaceutically acceptable acid.
13. Pharmaceutical composition, characterized in that it comprises a
compound of formula (I) according to any one of Claims 1 to 5, or a
pharmaceutically acceptable salt.
14. Use of a compound according to any one of Claims 1 to 5 for the
preparation of a medicament for preventing or treating obesity, diabetes,
appetite disorders and excess weight.
15. Compound according to any one of Claims 1 to 5, for preventing or
treating obesity, diabetes, appetite disorders and excess weight.
16. Combination comprising one or more compounds according to any one
of Claims 1 to 5 with one or more active ingredient(s).

The invention relates to disubstituted 3-benzofuranyl-indol-2-one-3-acetamidopiperazine derivatives of the
general formula (I) where R1, R2, R3, R4, R5, R6, R7, R8, R9 and n are such as defined in claim 1, to a method for preparing
same, and to the therapeutic use of said compounds.