Field of the Invention
[0001] The present invention provides compounds that are PDE10A enzyme inhibitors, and as
such are useful to treat neurodegenerative and psychiatric disorders. Especially,
the invention provides compounds that are highly selective for PDE10A enzyme over
other PDE subtypes. The present invention also provides pharmaceutical compositions
comprising compounds of the invention.
Background of the Invention
[0002] The cyclic nucleotides cyclic-adenosine monophosphate (cAMP) and cyclic-guanosine
monophosphate (cGMP) function as intracellular second messengers regulating a vast
array of processes in neurons. Intracellular cAMP and cGMP are generated by adenyl
and guanyl cyclases, and are degraded by cyclic nucleotide phosphodiesterases (PDEs)
via hydrolysis of the cyclic nucleotides into their respective nucleotide monophosphates.
[0003] Phosphodieasterase 10A (PDE10A) is a dual-specificity phosphodiesterase that can
convert both cAMP to AMP and cGMP to GMP (
Soderling, S. et al. Proc. Natl. Acad. Sci. 1999, 96, 7071-7076). PDE10A is primarily expressed in the neurons in the striatum, n. accumbens and
in the olfactory tubercle (
Kotera, J. et al. Biochem. Biophys. Res. Comm. 1999, 261, 551-557 and
Seeger, T.F. et al. Brain Research, 2003, 985, 113-126).
[0004] Studies indicate that within the brain, PDE10 expression is expressed at high levels
by the medium spiny neurons (MSN) of the caudate nucleus, the accumbens nucleus and
the corresponding neurons of the olfactory tubercle. MSN express two functional classes
of neurons: the D
1 class expressing D
1 dopamine receptors and the D
2 class expressing D
2 dopamine receptors. The D
1 class of neurons is part of the 'direct' striatal output pathway, which broadly functions
to facilitate behavioral responses. The D
2 class of neurons is part of the 'indirect' striatal output pathway, which functions
to suppress behavioral responses that compete with those being facilitated by the
'direct' pathway.
[0005] Dopamine D
2 receptor antagonism is well established in the treatment of schizophrenia. Since
the 1950's, dopamine D
2 receptor antagonism has been the mainstay in psychosis treatment and all effective
antipsychotic drugs antagonise D
2 receptors. The effects of D
2 are likely to be mediated primarily through neurons in the striatum, nucleus accumbens
and olfactory tubercle, since these areas receive the densest dopaminergic projections
and have the strongest expression of D
2 receptors (
Konradi, C. and Heckers, S. Society of Biological Psychiatry, 2001, 50, 729-742).
[0006] Because PDE10A, in this context, has the desired expression profile with high and
relatively specific expression in neurons in striatum, nucleus accumbens and olfactory
tubercle, PDE10A inhibition is likely to have effects similar to D
2 receptor antagonism and therefore have antipsychotic effects.
[0007] While PDE10A inhibition is expected to mimic D
2 receptor antagonism in part, it might be expected to have a different profile. The
D
2 receptor has signaling components besides cAMP (
Neve, K. A. et al. Journal of Receptors and Signal Transduction 2004, 24, 165-205), wherefore interference with cAMP through PDE10A inhibition may reduce the risk
of the extrapyramidal side effects that are seen with strong D
2 antagonism. Conversely, PDE10A inhibition may have some effects not seen with D
2 receptor antagonism. PDE10A is also expressed in D
1 receptors expressing striatal neurons (
Seeger, T. F. et al. Brain Research, 2003, 985, 113-126).
[0008] Further, since D
1 receptor agonism leads to stimulation of adenylate cyclase and resulting increase
in cAMP levels, PDE10A inhibition is likely to also have effects that mimic D
1 receptor agonism.
[0009] Finally, PDE10A inhibition will not only increase cAMP in cells, but might also be
expected to increase cGMP levels, since PDE10A is a dual specificity phosphodiesterase.
cGMP activates a number of target protein in cells like cAMP and also interacts with
the cAMP signaling pathways.
[0010] In conclusion, PDE10A inhibition is likely to mimic D
2 receptor antagonism in part and therefore has antipsychotic effect, but the profile
might differ from that observed with classical D
2 receptor antagonists.
[0011] The PDE10A inhibitor papaverine is shown to be active in several antipsychotic models.
Papaverine potentiated the cataleptic effect of the D
2 receptor antagonist haloperidol in rats, but did not cause catalepsy on its own (
WO 03/093499). Papaverine reduced hyperactivity in rats induced by PCP, while reduction of amphetamine
induced hyperactivity was insignificant (
WO 03/093499). These models suggest that PDE10A inhibition has the classic antipsychotic potential
that would be expected from the theoretical considerations outlined above.
WO 03/093499 further discloses the use of selective PDE10 inhibitors for the treatment of associated
neurologic and psychiatric disorders. Furthermore, PDE10A inhibition reverses subchronic
PCP-induced deficits in attentional set-shifting in rats (
Rodefer et al. Eur. J. Neurosci. 2005, 4, 1070-1076). This model suggests that PDE10A inhibition might alleviate cognitive deficits associated
with schizophrenia.
[0012] The tissue distribution of PDE10A indicates that PDE10A inhibitors can be used to
raise levels of cAMP and/or cGMP within cells that express the PDE10A enzyme, especially
neurons that comprise the basal ganglia, and the PDE10A inhibitors of the present
invention would therefore be useful in treating a variety of associated neuropsychiatric
conditions involving the basal ganglia such as neurological and psychiatric disorders,
schizophrenia, bipolar disorder, psychosis and obsessive compulsive disorder, and
may have the benefit of not possessing unwanted side effects, which are associated
with the current therapies on the market.
[0015] With respect to inhibitors of PDE10A,
EP 1250923 discloses the use of selective PDE10 inhibitors in general, and papaverine in particular,
for the treatment of certain neurologic and psychiatric disorders.
[0016] Pyrrolodihydroisoquinolines and variants thereof are disclosed as inhibitors of PDE10
in
WO 05/03129 and
WO 05/02579. Piperidinyl-substituted quinazolines and isoquinolines that serve as PDE10 inhibitors
are disclosed in
WO 05/82883.
WO 06/11040 discloses substituted quinazoline and isoquinoline compounds that serve as inhibitors
of PDE10.
US 20050182079 discloses substituted tetrahydroisoquinolinyl derivatives of quinazoline and isoquinoline
that serve as effective phosphodiesterase (PDE) inhibitors. In particular,
US 20050182079 relates to said compounds, which are selective inhibitors of PDE10. Analogously,
US 20060019975 discloses piperidine derivatives of quinazoline and isoquinoline that serve as effective
phosphodiesterase (PDE) inhibitors.
US 20060019975 also relates to compounds that are selective inhibitors of PDE10.
WO 06/028957 discloses cinnoline derivatives as inhibitors of PDE10 for the treatment of psychiatric
and neurological syndromes.
WO09/152825 discloses phenylimidazole derivatives as compounds that serve as inhibitors of PDE10.
WO2011/072694 discloses compounds comprising an imidazole group with two heteroaromatic groups
attached thereto as PDE10 inhibitors.
WO2010/145668 discloses the compound 5,8-Dimethyl-2-[2-(1-methyl-4-phenyl-1H-imidazol-2-yl)-ethyl]-[1,2,4]triazolo[1,5-a]pyrazine
as a PDE10 inhibitor.
WO2011/072695 discloses compounds comprising phenyl-imidazol linked to a heteroaromatic group via
ethynyl.
[0017] However, these disclosures do not pertain to the compounds of the invention, which
are structurally unrelated to any of the known PDE10 inhibitors (
Kehler, J. et al. Expert Opin. Ther. Patents 2007, 17, 147-158), and which have now been found by the inventors to be highly active and selective
PDE10A enzyme inhibitors.
[0018] The present invention provides compounds that are PDE10A enzyme inhibitors and thus
useful for treatment for neurodegenerative and/or psychiatric disorders, which are
not efficacious in all patients. Hence, there remains a need for alternative methods
of treatment.
Summary of the Invention
[0019] The objective of the present invention is to provide compounds that are selective
PDE10A enzyme inhibitors.
[0020] Another objective of the invention is to provide an effective treatment, in particular
long-term treatment, of a human patient, without causing the side effects typically
associated with current therapies for neurological and psychiatric disorders.
[0021] Further objectives of the invention will become apparent upon reading the present
specification.
[0022] Accordingly, in one aspect the present invention relates to compounds of formula
I

wherein
n is 0 or 1
X is CH,
R1 and R2 are each selected independently from the group consisting of H; C1-C6 alkyl
such as methyl, ethyl, 1-propyl, 2-propyl, isobutyl; C1-C6 alkyl(C3-C8)cycloalkyl
such as cyclopropylmethyl; C1-C6 hydroxyalkyl such as hydroxyethyl; C1-C6 alkoxy such
as methoxy and ethoxy; CH2CN; CH2C(O)NH2 ;C1-C6 arylalkyl such as benzyl and 4-chlorobenzyl;
and C1-C6 alkyl-heterocycloalkyl such as tetrahydropyran-4-yl-methyl and 2-morpholin-4-yl-ethyl;
halogen such as F; and hydroxy;
R3 and R4 are each selected independently from the group consisting of H, OH, F, CH3,
and OCH3.
[0023] Further, L is a linker selected from the group consisting of -CH=CH-, -CH
2-S-, -CH
2-CH
2- and -S-CH
2-; and
[0024] HET is a heteroaromatic group selected from the group consisting of [1,2,4]triazolo[1,5-a]pyrazine,
[1,2,4]triazolo[1,5-a]pyridine and [1,2,4]Triazolo[1,5-a]pyrimidine,HET can be substituted
with up to three substituents R5, R6 and R7 individually selected from the group consisting
of H, CH3, and OCH3.
[0025] In a preferred embodiment of the invention R1 and R2 are independently selected from
the group consisting of H, OH, F, CH3, and OCH3.
[0026] In another preferred embodiment of the invention R5, R6 and R7 are independently
selected from the group consisting of H, CH3, and OCH3.
[0027] In another preferred embodiment R1 and R2 are independently selected from the group
consisting of H, OH, F, CH3, and OCH3 while at the same time R5, R6 and R7 are independently
selected from the group consisting of H, CH3, and OCH3.
[0028] Further, the invention relates to tautomers and pharmaceutically acceptable acid
addition salts of a compound of formula I or II, and polymorphic forms thereof.
[0029] In a particular embodiment, the invention relates to a compound of formula I in the
form of a single tautomer or a polymorph.
[0030] In separate embodiments of the invention, the compound of formula I is selected among
the specific compounds disclosed in the examples of this application.
[0031] The invention further provides a compound of formula I, or a pharmaceutically acceptable
acid addition salt thereof, for use as a medicament.
[0032] In another aspect, the present invention provides a pharmaceutical composition comprising
a therapeutically effective amount of a compound of formula I and a pharmaceutically
acceptable carrier, diluent or excipient.
[0033] The invention further provides the use of a compound of formula I, or a pharmaceutically
acceptable acid addition salt thereof, for the preparation of a medicament for the
treatment of a neurodegenerative or psychiatric disorder.
Detailed Description of the Invention
Definition of Substitutents
[0034] As used in the context of the present invention, the terms "halo" and "halogen" are
used interchangeably and refer to fluorine, chlorine, bromine or iodine.
[0035] R1-R7 is short notation for the group consisting R1, R2, R3, R4, R5, R6, and R7.
Subsets of R1-R7 are defined similarly, e.g. R5-R7 means the group consisting R5,
R6, and R7.
[0036] The numbering of the substituents R1-R7 may also be specified by subscript, i.e.
R
1-R
7. Similarly the number of atoms (e.g. carbon atoms) may either be indicated by C1-C6
or by C
1-C
6, i.e. one to six carbon atoms.
[0037] The term "C
1-C
6 alkyl" refers to a straight-chain or branched saturated hydrocarbon having from one
to six carbon atoms, inclusive. Examples of such groups include, but are not limited
to, methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-2-propyl, 2-methyl-1-butyl,
and n-hexyl. The expression "C
1-C
6 hydroxyalkyl" refers to a C
1-C
6 alkyl group as defined above which is substituted with one hydroxy group. The term
"halo(C
1-C
6)alkyl" refers to a C
1-C
6 alkyl group as defined above which is substituted with up to three halogen atoms,
such as trifluoromethyl.
[0038] The expression "C
1-C
6 alkoxy" refers to a straight-chain or branched saturated alkoxy group having from
one to six carbon atoms, inclusive, with the open valency on the oxygen. Examples
of such groups include, but are not limited to, methoxy, ethoxy, n-butoxy, 2-methyl-pentoxy
and n-hexyloxy.
[0039] The term "C
3-C
8 cycloalkyl" includes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl
or cyclooctyl. The expression "C
1-C
6 alkyl(C
3-C
8)cycloalkyl" refers to a C
3-C
8 cycloalkyl as defined above which is substituted with a straight-chain or branched
C
1-C
6 alkyl. Examples of such groups include, but are not limited to, cyclopropylmethyl.
[0040] The term "heterocycloalkyl" refers to a four to eight membered ring containing carbon
atoms and up to three N, O or S atoms. The open valency is on either the heteroatom
or carbon atom. Examples of such groups include, but are not limited to, azetidinyl,
oxetanyl, piperazinyl, morpholinyl, thiomorpholinyl and [1,4]diazepanyl. The term
"hydroxyheterocycloalkyl" refers to a heterocycloalkyl as defined above which is substituted
with one hydroxy group. The term "C
1-C
6 alkyl-heterocycloalkyl" refers to a heterocycloalkyl as defined above which is substituted
with a C
1-C
6 alkyl group. Examples of such groups include, but are not limited to, tetrahydropyran-4-yl-methyl
and 2-morpholin-4-yl-ethyl.
[0041] The term "aryl" refers to a phenyl ring, optionally substituted with halogen, C
1-C
6 alkyl, C
1-C
6 alkoxy or halo(C
1-C
6)alkyl as defined above. Examples of such groups include, but are not limited to,
phenyl and 4-chlorophenyl.
[0042] The term "C
1-C
6 arylalkyl" refers to an aryl as defined above which is substituted with a straight-chain
or branched C
1-C
6 alkyl. Examples of such groups include, but are not limited to, benzyl and 4-chlorobenzyl.
[0043] In another embodiment of the invention L is -CH
2-CH
2-. In a further embodiment L is -CH
2-S-. In yet another embodiment L is -CH=CH-. In a still further embodiment L is -S-CH
2-.
[0044] In a further embodiment of the invention R1 and R2 are independently selected from
the group consisting of H, OH, F, CH3, and OCH3; and R5, R6 and R7 are independently
selected from the group consisting of H, CH3, and OCH3.
[0045] In a specific embodiment,
HET is 5,8-dimethyl-[1,2,4]triazole[1,5-a]pyrazine; L is -CH
2-CH
2- ; R1 and R2 are independently selected from the group consisting of H, OH, F, CH3,
and OCH3, in particular R1 and R2 are H; n=0 and R3 and R4 are therefore absent; and
R5, R6 and R7 are independently selected from the group consisting of H, CH3, and
OCH3, in particular R5 is CH3, R6 is H and R7 is CH3.
[0046] In separate embodiments of the invention, the compound of formula I is selected among
the following specific compounds, in the form of the free base, one or more tautomers
thereof or a pharmaceutically acceptable acid addition salt thereof.
[0047] In a specific embodiment of any of the previously mentioned embodiments one or more
of the hydrogen atoms of the compound are replaced by deuterium.
[0048] Table 1 lists compounds of the invention and the corresponding IC
50 values determined as described in the section "PDE10A inhibition assay". Each of
the compounds constitutes an individual embodiment, of the present invention:
Table 1: Compounds of the invention and IC
50 values
| Compound |
PDE10 IC50 (nM) |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole |
0.4 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyridin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole |
0.69 |
| 2-[2-(5-Methyl-[1,2,4]triazolo[1,5-a]pyridin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole |
6.1 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-5H-imidazo[2,1-a]isoindole |
4.4 |
| {2-[2-(5H-lmidazo[2,1-a]isoindol-2-yl)-ethyl]-5-methyl-[1,2,4]triazolo[1,5-a]pyrazin-8-yl}-methanol |
6.9 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-7-fluoro-5H-imidazo[2,1-a]isoindole |
0.18 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5,6-dihydro-imidazo[2,1-a]isoquinoline |
0.81 |
| 2-[2-(5,8-Dimethyl-7-oxy-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole |
2.4 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-8-fluoro-5H-imidazo[2,1-a]isoindole |
3.1 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-7-methoxy-5H-imidazo[2,1-a]isoindole |
0.29 |
| 2-{2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindol-5-yl}-propan-2-ol |
21 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-6-fluoro-5H-imidazo[2,1-a]isoindole |
1.2 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-9-fluoro-5H-imidazo[2,1-a]isoindole |
0.79 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-8-methoxy-5H-imidazo[2,1-a]isoindole |
6.9 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-6-methoxy-5H-imidazo[2,1-a]isoindole |
0.44 |
| 2-[2-(5,8-Bis(trideuteromethyl)-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5,5-dideutero-5H-imidazo[2,1-a]isoindole |
0.4 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-9-methoxy-5H-imidazo[2,1-a]isoindole |
0.44 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine |
46 |
| 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[1',2':1,5]pyrrolo[3,4-b]pyridine |
3.8 |
| 2-([1,2,4]Triazolo[1,5-a]pyridin-2-ylsulfanylmethyl)-5H-imidazo[2,1-a]isoindole |
5300 |
| 2-[(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)sulfanylmethyl]-5H-imidazo[2,1-a]isoindole |
260 |
| 2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-ylsulfanylmethyl)-5H-imidazo[2,1-a]isoindole |
n.d. |
[0049] In a particular embodiment of the present invention the compounds of the present
invention have an IC
50 value of less than 20 nM, such as in the range of 0.1 - 20 nM, particularly in the
range of 0.1 - 10 nM, such as in the range of 0.1 - 5 nM or in the range of 0.1 -
1 nM.
Pharmaceutically Acceptable Salts
[0050] The present invention also comprises salts of the compounds, typically, pharmaceutically
acceptable salts. Such salts include pharmaceutically acceptable acid addition salts.
Acid addition salts include salts of inorganic acids as well as organic acids.
[0051] Representative examples of suitable inorganic acids include hydrochloric, hydrobromic,
hydroiodic, phosphoric, sulfuric, sulfamic, nitric acids and the like. Representative
examples of suitable organic acids include formic, acetic, trichloroacetic, trifluoroacetic,
propionic, benzoic, cinnamic, citric, fumaric, glycolic, itaconic, lactic, methanesulfonic,
maleic, malic, malonic, mandelic, oxalic, picric, pyruvic, salicylic, succinic, methane
sulfonic, ethanesulfonic, tartaric, ascorbic, pamoic, bismethylene salicylic, ethanedisulfonic,
gluconic, citraconic, aspartic, stearic, palmitic, EDTA, glycolic, p-aminobenzoic,
glutamic, benzenesulfonic, p-toluenesulfonic acids, theophylline acetic acids, as
well as the 8-halotheophyllines, for example 8-bromotheophylline and the like. Further
examples of pharmaceutically acceptable inorganic or organic acid addition salts include
the pharmaceutically acceptable salts listed in
Berge, S.M. et al., J. Pharm. Sci. 1977, 66, 2.
[0052] Furthermore, the compounds of this invention may exist in unsolvated as well as in
solvated forms with pharmaceutically acceptable solvents such as water, ethanol and
the like. In general, the solvated forms are considered equivalent to the unsolvated
forms for the purposes of this invention.
Pharmaceutical compositions
[0053] The present invention further provides a pharmaceutical composition comprising a
therapeutically effective amount of a compound of formula I and a pharmaceutically
acceptable carrier or diluent. The present invention also provides a pharmaceutical
composition comprising a therapeutically effective amount of one of the specific compounds
disclosed in the Experimental Section herein and a pharmaceutically acceptable carrier
or diluent.
[0055] The pharmaceutical compositions may be specifically formulated for administration
by any suitable route such as oral, rectal, nasal, pulmonary, topical (including buccal
and sublingual), transdermal, intracisternal, intraperitoneal, vaginal and parenteral
(including subcutaneous, intramuscular, intrathecal, intravenous and intradermal)
routes. It will be appreciated that the route will depend on the general condition
and age of the subject to be treated, the nature of the condition to be treated and
the active ingredient.
[0056] Pharmaceutical compositions for oral administration include solid dosage forms such
as capsules, tablets, dragees, pills, lozenges, powders and granules. Where appropriate,
the compositions may be prepared with coatings such as enteric coatings or they may
be formulated so as to provide controlled release of the active ingredient such as
sustained or prolonged release according to methods well known in the art. Liquid
dosage forms for oral administration include solutions, emulsions, suspensions, syrups
and elixirs.
[0057] Pharmaceutical compositions for parenteral administration include sterile aqueous
and nonaqueous injectable solutions, dispersions, suspensions or emulsions as well
as sterile powders to be reconstituted in sterile injectable solutions or dispersions
prior to use. Other suitable administration forms include, but are not limited to,
suppositories, sprays, ointments, creams, gels, inhalants, dermal patches and implants.
[0058] Typical oral dosages range from about 0.001 to about 100 mg/kg body weight per day.
Typical oral dosages also range from about 0.01 to about 50 mg/kg body weight per
day. Typical oral dosages further range from about 0.05 to about 10 mg/kg body weight
per day. Oral dosages are usually administered in one or more dosages, typically,
one to three dosages per day. The exact dosage will depend upon the frequency and
mode of administration, the sex, age, weight and general condition of the subject
treated, the nature and severity of the condition treated and any concomitant diseases
to be treated and other factors evident to those skilled in the art.
[0059] The formulations may also be presented in a unit dosage form by methods known to
those skilled in the art. For illustrative purposes, a typical unit dosage form for
oral administration may contain from about 0.01 to about 1000 mg, from about 0.05
to about 500 mg, or from about 0.5 mg to about 200 mg.
[0060] For parenteral routes such as intravenous, intrathecal, intramuscular and similar
administration, typical doses are in the order of half the dose employed for oral
administration.
[0061] The present invention also provides a process for making a pharmaceutical composition
comprising admixing a therapeutically effective amount of a compound of formula I
and at least one pharmaceutically acceptable carrier or diluent. In an embodiment,
of the present invention, the compound utilized in the aforementioned process is one
of the specific compounds disclosed in the Experimental Section herein.
[0062] The compounds of this invention are generally utilized as the free substance or as
a pharmaceutically acceptable salt thereof. One example is an acid addition salt of
a compound having the utility of a free base. When a compound of formula I contains
a free base such salts are prepared in a conventional manner by treating a solution
or suspension of a free base of formula I with a molar equivalent of a pharmaceutically
acceptable acid. Representative examples of suitable organic and inorganic acids are
described above.
[0063] For parenteral administration, solutions of the compounds of formula I in sterile
aqueous solution, aqueous propylene glycol, aqueous vitamin E or sesame or peanut
oil may be employed. Such aqueous solutions should be suitably buffered if necessary
and the liquid diluent first rendered isotonic with sufficient saline or glucose.
The aqueous solutions are particularly suitable for intravenous, intramuscular, subcutaneous
and intraperitoneal administration. The compounds of formula I may be readily incorporated
into known sterile aqueous media using standard techniques known to those skilled
in the art.
[0064] Suitable pharmaceutical carriers include inert solid diluents or fillers, sterile
aqueous solutions and various organic solvents. Examples of solid carriers include
lactose, terra alba, sucrose, cyclodextrin, talc, gelatin, agar, pectin, acacia, magnesium
stearate, stearic acid and lower alkyl ethers of cellulose. Examples of liquid carriers
include, but are not limited to, syrup, peanut oil, olive oil, phospholipids, fatty
acids, fatty acid amines, polyoxyethylene and water. Similarly, the carrier or diluent
may include any sustained release material known in the art, such as glyceryl monostearate
or glyceryl distearate, alone or mixed with a wax. The pharmaceutical compositions
formed by combining the compounds of formula I and a pharmaceutically acceptable carrier
are then readily administered in a variety of dosage forms suitable for the disclosed
routes of administration. The formulations may conveniently be presented in unit dosage
form by methods known in the art of pharmacy.
[0065] Formulations of the present invention suitable for oral administration may be presented
as discrete units such as capsules or tablets, each containing a predetermined amount
of the active ingredient, and optionally a suitable excipient. Furthermore, the orally
available formulations may be in the form of a powder or granules, a solution or suspension
in an aqueous or non-aqueous liquid, or an oil-in-water or water-in-oil liquid emulsion.
[0066] If a solid carrier is used for oral administration, the preparation may be tabletted,
placed in a hard gelatin capsule in powder or pellet form or it may be in the form
of a troche or lozenge. The amount of solid carrier will vary widely but will range
from about 25 mg to about 1 g per dosage unit. If a liquid carrier is used, the preparation
may be in the form of a syrup, emulsion, soft gelatin capsule or sterile injectable
liquid such as an aqueous or non-aqueous liquid suspension or solution.
[0067] The pharmaceutical compositions of the invention may be prepared by conventional
methods in the art. For example, tablets may be prepared by mixing the active ingredient
with ordinary adjuvants and/or diluents and subsequently compressing the mixture in
a conventional tabletting machine prepare tablets. Examples of adjuvants or diluents
comprise: corn starch, potato starch, talcum, magnesium stearate, gelatin, lactose,
gums, and the like. Any other adjuvants or additives usually used for such purposes
such as colorings, flavorings, preservatives etc. may be used provided that they are
compatible with the active ingredients.
Treatment of Disorders
[0068] As mentioned above, the compounds of formula I are PDE10A enzyme inhibitors and as
such are useful to treat associated neurological and psychiatric disorders.
[0069] The invention thus provides a compound of formula I or a pharmaceutically acceptable
acid addition salt thereof, as well as a pharmaceutical composition containing such
a compound, for use in the treatment of a neurodegenerative disorder, psychiatric
disorder or drug addiction in humans.
[0070] In one embodiment of the present invention, the neurodegenerative disorder or condition
involves neurodegeneration of striatal medium spiny neurons in a human. In a specific
embodiment of the present invention, the neurodegenerative disorder or condition is
Huntington's disease. In a further embodiment the disorder is dyskinesia associated
with dopamine agonist therapy.
[0071] In an embodiment the psychiatric disorder is selected from the group consisting of
schizophrenia, for example of the paranoid, disorganized, catatonic, undifferentiated,
or residual type; schizophreniform disorder; schizoaffective disorder, for example
of the delusional type or the depressive type; delusional disorder; substance-induced
psychotic disorder, for example psychosis induced by alcohol, amphetamine, cannabis,
cocaine, hallucinogens, inhalants, opioids, or phencyclidine; personality disorder
of the paranoid type; and personality disorder of the schizoid type.
[0072] The term "drug addiction", as used herein, means an abnormal desire for a drug and
is generally characterized by motivational disturbances such a compulsion to take
the desired drug and episodes of intense drug craving.
[0073] Drug addiction is widely considered a pathological state. The disorder of addiction
involves the progression of acute drug use to the development of drug-seeking behavior,
the vulnerability to relapse, and the decreased, slowed ability to respond to naturally
rewarding stimuli. For example,
The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) has categorized three stages of addiction: preoccupation/anticipation, binge/intoxication,
and withdrawal/negative affect. These stages are characterized, respectively, everywhere
by constant cravings and preoccupation with obtaining the substance; using more of
the substance than necessary to experience the intoxicating effects; and experiencing
tolerance, withdrawal symptoms, and decreased motivation for normal life activities.
[0074] Other disorders that can be treated according to the present invention are obsessive/compulsive
disorders, non-insuline demanding diabetes mellitus (NIDDM), and Tourette's syndrome
and other tic disorders as well as Attention Deficit/Hyperactivity Disorder (ADHD).
[0075] The compounds of formula I or pharmaceutically acceptable salts thereof may be used
in combination with one or more other drugs (including typical and atypical antpsychotic
agent) in the treatment of diseases or conditions for which the compounds of the present
invention have utility, where the combination of the drugs together are safer or more
effective than either drug alone. Additionally, the compounds of the present invention
may be used in combination with one or more other drugs that treat, prevent, control,
ameliorate, or reduce the risk of side effects or toxicity of the compounds of the
present invention. The combinations, uses and methods of treatment of the invention
may also provide advantages in treatment of patients who fail to respond adequately
or who are resistant to other known treatments.
[0076] Such other drugs may be administered, by a route and in an amount commonly used therefore,
contemporaneously or sequentially with the compounds of the present invention. Accordingly,
the pharmaceutical compositions of the present invention include those that contain
one or more other active ingredients, in addition to the compounds of the present
invention. The combinations may be administered as part of a unit dosage form combination
product, or as a kit or treatment protocol wherein one or more additional drugs are
administered in separate dosage forms as part of a treatment regimen.
[0077] The term "neuroleptic agent" as used herein refers to drugs, which have the effect
on cognition and behaviour of antipsychotic agent drugs that reduce confusion, delusions,
hallucinations, and psychomotor agitation in patients with psychoses. Also known as
major tranquilizers and antipsychotic drugs, neuroleptic agents include, but are not
limited to: typical antipsychotic drugs, including phenothiazines, further divided
into the aliphatics, piperidines, and piperazines, thioxanthenes (e.g., cisordinol),
butyrophenones (e.g., haloperidol), dibenzoxazepines (e.g., loxapine), dihydroindolones
(e.g., molindone), diphenylbutylpiperidines (e.g., pimozide), and atypical antipsychotic
drugs, including benzisoxazoles (e.g., risperidone), sertindole, olanzapine, quetiapine,
osanetant and ziprasidone.
[0078] Particularly preferred neuroleptic agents for use in the invention are sertindole,
olanzapine, risperidone, quetiapine, aripiprazole, haloperidol, clozapine, ziprasidone
and osanetant.
[0079] As used herein, and unless otherwise indicated, a "neurodegenerative disorder or
condition" refers to a disorder or condition that is caused by the dysfunction and/or
death of neurons in the central nervous system. The treatment of these disorders and
conditions can be facilitated by administration of an agent which prevents the dysfunction
or death of neurons at risk in these disorders or conditions and/or enhances the function
of damaged or healthy neurons in such a way as to compensate for the loss of function
caused by the dysfunction or death of at-risk neurons. The term "neurotrophic agent"
as used herein refers to a substance or agent that has some or all of these properties.
[0080] Headings and sub-headings are used herein for convenience only, and should not be
construed as limiting the invention in any way.
Experimental Section
Preparation of the compounds of the invention
[0081] Compounds of the general formula
I of the invention may be prepared as described in the following reaction schemes.
[0082] Compounds of formula
I, wherein L is -CH
2-S-, can be prepared by the coupling of a nucleophile of formula
III with an electrophile of formula
IV, where
Q is a leaving group,
e.g. Cl, Br, I, methanesulfonyl, 4-toluenesulfonyl, as shown in scheme 1.

[0083] This reaction is typically carried out in a solvent such as 1-propanol, toluene,
DMF, or acetonitrile, optionally in the presence of a carbonate base such as potassium
carbonate or a tertiary amine base such as triethylamine or diisopropylethylamine
(DIPEA), at a temperature ranging from about 0°C to about 200°C, optionally under
pressure in a closed vessel. Other suitable solvents include benzene, chloroform,
dioxane, ethyl acetate, 2-propanol and xylene. Alternatively, solvent mixtures such
as toluene/2-propanol can be used.
[0084] Thiol-compounds of formula
III can be made by methods similar to those described in the literature e.g.
Journal of Heterocyclic Chemistry 1977 14(5), 889-92,
Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry
1979, 5, 1132-6,
Journal of the Chemical Society, Perkin Transactions 1: Organic and Bio-Organic Chemistry
1997, 20, 2983-2988,
Organic & Biomolecular Chemistry 2009, 7, 128-134.
[0085] Some electrophiles of formula
IV are commercially available, and many others are known in the art, see for example
JP 59176277 and
US 2010016303. The electrophile
IV, where Q is a leaving group, e.g. Cl, Br, I, methanesulfonyl, 4-toluenesulfonyl, can
also be prepared by conversion of the corresponding primary alcohol to said leaving
group by methods known to chemists skilled in the art. Said methods can for example
be selected from reacting compounds of the corresponding primary alcohol with thionyl
chloride, phosphorous trichloride, phosphorous tribromide, methanesulfonyl chloride,
or 4-toluenesulfonyl chloride optionally in the presence of a suitable solvent, such
as dichloromethane or 1,2-dichloroethane, and optionally in the presence of a base,
such as triethylamine, diisopropylethylamine, or pyridine. Alternatively, electrophiles
of formula
IV can be prepared by reacting commercially available heteroaromatic amines with 1,3-dihaloacetones
of, e.g. 1,3-dichloroacetone, in a suitable solvent, such as 1,2-dimethoxyethane or
ethanol, at a suitable temperature, such as room temperature or reflux. Some electrophiles
of formula
IV are commercially available, and many others are known in the art, see for example
Tsuchiya, T.; Sashida, H. J. Chem. Soc., Chem. Commun. 1980, 1109-1110;
Tsuchiya, T.; Sashida, H; Konoshita, A. Chem. Pharm. Bull. 1983, 31, 4568-4572.
[0086] Compounds of formula
I, wherein L is -S-CH
2-, can be prepared by the coupling of a nucleophile of formula
V or
Va with an electrophile of formula
VI, where
Q is a leaving group, e.g. Cl, Br,
I, methanesulfonyl, 4-toluenesulfonyl, as shown in scheme 2. In the reaction between
V and
Va with
VI, alkylation of the sulfur atom of
V or
Va with
VI and ring closure to form the triazole ring both take place under the same reaction
conditions in a one-pot procedure.

[0087] This reaction is typically carried out in a solvent such as 1-propanol, toluene,
DMF, or acetonitrile, optionally in the presence of a carbonate base such as potassium
carbonate or a tertiary amine base such as triethylamine or diisopropylethylamine
(DIPEA), at a temperature ranging from about 0°C to about 200°C, optionally under
pressure in a closed vessel. Other suitable solvents include benzene, chloroform,
dioxane, ethyl acetate, 2-propanol and xylene. Alternatively, solvent mixtures such
as toluene/2-propanol can be used.
[0088] Compounds of formula
V are either commercially available or can be prepared as described in the literature,
see for example
Brown et al. Aust. J. Chem. 1978, 31, 397-404;
Yutilov et al. Khim. Geter. Soedin. 1988, 799-804; Wilde et al. Bioorg. Med. Chem. Lett. 1995, 5, 167-172;
Kidwai et al. J. Korean Chem. Soc. 2005, 49, 288-291. Compounds of formula
Va can be prepared as described in
WO 96/01826 from the corresponding 1,2-diaminopyridines by reaction with thiocarbonyldiimidazole
in a suitable solvent, such as chloroform, at a suitable temperature, such as room
temperature or +40°C. The requisite 1,2-diaminopyridines are readily available from
the corresponding commercially available 2-aminopyridines by reaction with a suitable
N-amination reagent, such as
O-(mesitylsulfonyl)hydroxylamine, in a suitable solvent, such as chloroform, at a suitable
temperature, such as 0°C or room temperature, see
WO 96/01826.
[0090] Compounds of formula
I, wherein L is -CH=CH- or -CH
2-CH
2- can be prepared by the reaction sequence shown in scheme 3.

[0091] Specifically, compounds of formula
I, wherein L is -CH
2-CH
2- can be prepared by reduction of an alkene of formula
I, wherein L is -CH=CH-, by hydrogenation using a transition metal catalyst, such as
palladium metal, together with a hydrogen source, such as hydrogen gas, ammonium hydrogen
carbonate, or cyclohexadiene. Said alkenes of formula
I, wherein L is -CH=CH- can be prepared by the Wittig reaction between a phosphonium
salt of formula
VII and an aldehyde of formula
VIII in a suitable solvent, such as tetrahydrofuran, in the presence of a suitable base,
such as 1,8-diazabicyclo[5.4.0]undec-7-ene. Phosphonium salt of formula
VII are readily available by reaction of compounds of formula
IV (see scheme 1 above) with triphenylphosphine by methods known to chemists skilled
in the art. Aldehydes of formula
VIII are available by methods described in the literature se e.g.
Venkatesan, A. et al. ChemMedChem 2008, 3, 1658-1661.
General Methods
[0092] Analytical LC-MS data were obtained using the following method:
A PE Sciex API 150EX instrument equipped with atmospheric pressure photo ionisation
and a Shimadzu LC-8A/SLC-10A LC system was used. Column: 4.6 x 30 mm Waters Symmetry
C18 column with 3.5 micro m particle size; Column temperature: 60°C; Solvent system:
A = water/trifluoroacetic acid (99.95:0.05) and B = methanol/trifluoroacetic acid
(99.965:0.035); Method: Linear gradient elution with A:B = 83:17 to 0:100 in 2.4 minutes
and with a flow rate of 3.0 mL/minute.
[0093] Preparative LC-MS-purification was performed on a PE Sciex API 150EX instrument with
atmospheric pressure chemical ionization. Column: 50 X 20 mm YMC ODS-A with 5 micro
m particle size; Method: Linear gradient elution with A:B = 80:20 to 0:100 in 7 minutes
and with a flow rate of 22.7 mL/minute. Fraction collection was performed by split-flow
MS detection.
1H NMR spectra were recorded at 500.13 MHz on a Bruker Avance AV500 instrument or at
600.16 MHz on a Bruker Avance Ultrashield plus instrument. TMS was used as internal
reference standard. Chemical shift values are expressed in ppm. The following abbreviations
are used for multiplicity of NMR signals: s = singlet, d = doublet, t = triplet, q
= quartet, qui = quintet, h = heptet, dd = double doublet, dt = double triplet, dq
= double quartet, td = triplet of doublets, tt = triplet of triplets, m = multiplet,
br s = broad singlet and br = broad signal.
Preparation of intermediates
5H-Imidazo[2,1-a]isoindole-2-carbaldehyde
[0095]

[0096] A solution of compound
1 (19 g, 0.097 mol) and potassium phthalimide (18 g, 0.097 mol) in DMF (100 mL) was
heated at 100°C for 1 hour. The mixture was poured into water (500 mL) and the solids
filtered and washed with water. The solids were dried under vacuum to give compound
2 (21 g, yield: 65%) as a white solid.
1H NMR (400 MHz, CDCl
3):
δ7.89-7.87 (m, 2H), 7.76-7.74 (m, 2H), 7.67 (d,
J = 6.8Hz, 2H), 7.51 (t,
J = 7.6Hz, 1H), 7.37 (t,
J = 8.0Hz, 2H), 5.09 (s, 2H).

[0097] A mixture of compound
2 (21 g, 0.080 mol) and KOH (13 g, 0.230 mol) in EtOH (150 mL) was heated at 80°C for
0.5 hour. The thick mixture was cooled and filtered. The filtrate was diluted with
water (1 L) and extracted with EtOAc (200 mLx2). The combined organic layers were
dried over Na
2SO
4 and concentrated to give crude compound
3 (8.05 g, 63%) as a brown solid.

[0098] A mixture of compound
4 (3.9 g, 26.9 mmol),
i-PrOH (7.8 mL), TsOH.H
2O (73 mg, 0.38 mmol) and hexane (49 mL) was distilled (atmospheric pressure, reaction
temperature 67°C) to remove the solvent, the remaining 27 mL of solution was further
distilled in vacuum (∼8.5 kPa, reaction temperature 25°C) to afford the crude product
5 (5.0 g) as a brown liquid, which was unstable and used in the next step directly.

[0099] A solution of crude compound
3 (8.05 g, 0.061 mol) and crude compound
5 (11.8 g, 0.061) was stirred at room temperature for 20 hours, then potassium carbonate
(16.8 g, 122 mmol) was added to the mixture and heated to reflux for 2 hours. The
reaction solution was concentrated, the residue was purified by column chromatography
on silica gel (n-heptane/EtOAc, 1:1 to 100% EtOAc) to give
6 (2.00 g, yield: 6.95%) as a yellow solid.
1H NMR (400 MHz, CDCl
3):
δ 9.89 (s, 1H), 7.88-7.83 (m, 2H), 7.45-7.43 (m, 2H), 7.39-7.37 (m, 1H), 4.93 (s, 2H).
[0100] The following intermediates were prepared in a similar way:
7-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde, 1H NMR (600 MHz, CDCl3): δ 9.93 (s, 1H), 7.92 (s, 1H), 7.91-7.89 (m, 1H), 7.26-7.21 (m, 2H), 5.03 (s, 2H). LC-MS
(MH+): m/z = 203.0, tR (minutes) =0.53.
8-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde, 1H NMR (600 MHz, CDCl3): δ 9.94 (s, 1H), 7.93 (s, 1H), 7.62 (dd, J = 8.0, 2.4 Hz, 1H), 7.48 (dd, J = 8.5, 4.5 Hz, 1H), 7.16 (td, J = 8.5, 2.4 Hz, 1H), 5.02 (s, 2H). LC-MS (MH+): m/z = 203.1, tR (minutes) =0.64.
7-Methoxy-5H-imidazo[2,1-a]isoindole-2-carbaldehyde, 1H NMR (600 MHz, CDCl3): δ 9.91 (s, 1H), 7.88 (s, 1H), 7.86 - 7.83 (m, 1H), 7.05 - 7.02 (m, 2H), 4.98 (s, 2H),
3.89 (s, 3H). LC-MS (MH+): m/z = 215.0, tR (minutes) =0.47.
5,6-Dihydro-imidazo[2,1-a]isoquinoline-2-carbaldehyde
[0101]

[0102] A solution of compound
7 (4.92 g, 0.037 mol) in toluene (100 mL) was treated with triethylamine (10.2 mL,
0.073 mol) and the solution cooled to 0°C. Methane sulfonyl chloride (2.87 mL, 0.037
mol) was added, after stirring at this temperature for 10 minutes the solution was
allowed to warm to room temperature and stirred for 16 hours. The mixture was poured
into water (250 mL) and extracted with DCM (250 mL x 2). The combined organic layers
were dried over MgSO
4 and concentrated to give crude compound
8 (7.05 g) as a brown liquid.
1H NMR (500 MHz, DMSO-
d6):
δ7.59 (d,
J = 7.8Hz, 2H), 7.44 (d,
J = 7.8Hz, 2H), 7.38 (t,
J = 7.8Hz, 2H), 7.23 (t,
J = 7.8Hz, 1H), 4.43 (t,
J = 6.8Hz, 2H), 3.14 (t,
J = 6.8Hz, 2H), 3.12 (s, 3H).

[0103] Methyl 4-imidazolecarboxylate (1.09 g, 8.62 mmol) was slowly added to a suspension
of sodium hydride (60% dispersion in oil, 0.52 g, 13 mmol) in DMF (40 mL). The mixture
was heated to 80°C and stirred at this temperature for 1 hour. A solution of compound
8 (3.61 g, 12.90 mmol) in DMF (20 mL) was added dropwise to the reaction mixture at
this temperature and the reaction mixture stirred a further 12 hours at 80°C. The
cooled mixture was filtered, the volatiles removed in vacuo and the residue purified
by column chromatography on silica gel (100% n-heptane to 100% EtOAc) to yield compound
10 (0.91 g, 34 %) as a yellow semi solid first LC-MS (MH
+):
m/
z = 311.3,
tR (min, ) =1.15 then compound
9 (1.38 g, yield: 51 %) as a yellow solid LC-MS (MH
+):
m/
z = 311.3,
tR (minutes) =1.16.

[0104] To a solution of 1-[2-(2-bromophenyl)ethyl]-1H-imidazole-4-carboxylic acid methyl
ester (1.38 g, 4.46 mmol) in toluene (20 mL) degassed with argon and heated to 100°C
was added a solution of tributylgermanium hydride in toluene (10 mL) degassed with
argon. 2,2'-Azo-bis-isobutyronitrile (0.88 g, 5.36 mmol) was added and the reaction
stirred at 110°C for 16 h. A further 2'-azo-bis-isobutyronitrile (0.88 g, 5.36 mmol)
was added and the reaction stirred at 110°C for 4 h. The reaction was quenched by
pouring into 1 M HCl solution (100 mL), the two phases were separated and the aqueous
phase treated extracted with n-heptane (2 x 100 mL). The aqueous phase was basified
with saturated sodium bicarbonate solution and extracted with DCM (3 x 100 mL). The
combined organics were dried over MgSO
4, filtered and the volatiles removed in vacuo and the residue purified by column chromatography
on silica gel (100% n-heptane to 100% EtOAc) to yield compound
11 (124 mg, 13 %) LC-MS (MH
+):
m/
z = 229.2,
tR (minutes) =0.86.

[0105] To a solution of 5,6-dihydroimidazo[2,1-a]isoquinoline-2-carboxylic acid methyl ester
(210 mg, 0.92 mmol) in THF (9.6 mL) under an atmosphere of nitrogen was added a 1M
solution of LiAlH
4 in THF (1.1 mL) and the solution stirred at room temperature for 2 h. Water (0.5
mL) was added followed by EtOAc (50 mL) and the solution dried with MgSO
4, filtered and the volatiles removed in vacuo to yield compound
12 (177 mg, 96 %) LC-MS (MH
+):
m/
z = 201.2,
tR (minutes) =0.29.

[0106] To a solution of (5,6-dihydroimidazo[2,1-a]isoquinolin-2-yl)-methanol (177 mg, 0.88
mmol) in DCM (10 mL) under an atmosphere of argon was added Dess-Martin periodinane
(41 mg, 0.97 mmol) and the solution stirred at room temperature for 2 h. The reaction
was diluted with EtOAc (100 mL) and washed with saturated sodium bicarbonate solution
(3 x 50 mL), brine (50 mL) then dried with Na
2SO
4, filtered and the volatiles removed in vacuo to yield crude compound
13 (165 mg, 94 %) LC-MS (MH
+):
m/
z = 199.0,
tR (minutes) =0.55.
2-Chloromethyl-5,8-dimethyl-[1,2,4]triazolo[1,5-a]pyridine
[0107]

[0108] To a solution of 3,6-Dimethyl-2-pyridinamine (2.00 g, 16.4 mmol) in 50 mL of DCM
was added dropwise a solution of hydroxylamine-2,4,6-Trimethyl-benzenesulfonate (4.22
g, 19.6 mmol) in 50 mL of CH
2Cl
2 at 0°C, and the mixture was stirred and allowed to warm to room temperature. The
solvents were evaporated and the residue dissolved in 80 mL of MeOH then treated with
DBU (3.43 mL, 22.9 mmol) and the solution stirred for 5 mins. After chloroacetic acid
methyl ester (1.44 mL, 16.4 mmol) was added, the resultant mixture was stirred at
room temperature for 48 h. After being concentrated under reduce pressure, the residue
was diluted with water (100 mL) and extracted with EtOAc (3 x 100 mL). The combined
organic layers were washed with water (50 mL), brine (50 mL), dried over MgSO
4, filtered, and concentrated under vacuum. The residue was purified by column chromatography
on silica gel (petroleum ether/EtOAc = 2/1) to give 2.65 g of 2-Chloromethyl-5,8-dimethyl-[1,2,4]triazolo[1,5-a]pyridine
in 82% yield. LC-MS (MH
+):
m/
z = 195.9,
tR (minutes) =1.14
[0109] The following intermediates were prepared analogously:
2-Chloromethyl-5-methyl-[1,2,4]-triazolo[1,5-a]pyrazine from 2-amino-6-methylpyrazine.
28% yield, LC-MS: m/z = 181.8 (MH+), tR = 0.64 min
2-Chloromethyl-5,8-dimethyl-[1,2,4]-triazolo[1,5-a]pyrazine from 2-amino-3,6-dimethylpyrazine.
60% yield, 1H NMR (500 MHz, CDCl3): δ7.91 (s,1H), 4.87 (s, 2H), 2.91 (s, 3H), 2.74 (s, 3H), LC-MS: m/z = 196.9 (MH+), tR = 0.64 min
6-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
[0110]

[0111] A solution of the compound
2A (50 g, 0.37 mol) in CCl
4 (500 mL) was added the NBS (72.5 g, 0.408 mol) and the AIBN (1.2 g, 0.037 mol), the
reaction solution was refluxed for overnight, TLC indicated the reaction was completed,
the reaction solution was filtered and concentrated in vacuum to give the crude product
which was purified by flash silica chromatography eluting with petroleum ether/EtOAc
(500:1) to give the desired compound
2B (30 g, yield: 40%) as a white solid.
[0112] To a solution of compound
2B (60 g, 0.28 mol) and compound
1C (78 g, 0.44 mol) in DMF (500 mL) was added Cs
2CO
3 (150 g, 0.46 mol). The mixture was stirred at r.t (12 °C) for 2 hours. TLC indicated
that all the starting material
2B was consumed completely. The mixture was poured into water (2 L), the precipitated
product was filtered, washed with water (500 mL) and methanol (500 mL) to give the
product
2C (85 g, yield: 92%) as a white solid.
[0113] A mixture of compound 2C (130 g, 0.466 mol) and KOH (80 g, 1.43 mol) in EtOH (1.8
L) was heated at 90°C for 0.5 hour. TLC showed that the reaction was completed. The
mixture was cooled and filtered, the yellowish filtrate was concentrated in vacuum
to give a brown solid, which was diluted with EtOAc (1 L) and water (300 mL), the
aqueous layer was extracted by EtOAc (300 mLx5), the combined organic layer was washed
by brine (300 mL), dried over anhydrous Na
2SO
4, concentrated in vacuum to give the product
2D (65 g, crude) as brown solid, which is pure enough for next step reaction. A mixture
of compound
2D (25 g, crude) and compound 1 F (43 g, 0.185 mol) in dry CH
3CN (500 mL) was stirred at r.t. (27°C) overnight. The resulting mixture was filtered
and washed with MeCN, and dired in vacuum over to afford compound
2E (37 g, yield: 85%). A solution of compound
2E (23 g, 60 mmol) and Et
3N (7.27 g, 72 mmol) in dry CH
3CN (400 mL) was stirred at 90°C -100 °C reflux for 18 hours. The reaction solution
was concentrated. The residue was diluted with EtOAc, and washed with 20% aqueous
potassium hydrogen carbonate solution. After filtration through a pad of Celite, the
organic layer was dried (MgSO
4) and concentrated in vacuum. The residue was purified by silica column chromatography
(eluted with PE:EtOAc = 5:1) to give 6-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
(1.1 g, yield: 10%) as a yellowish solid.
1H NMR (CDCl
3 400 MHz):
δ9.9 (s, 1H), 7.89 (s, 1H), 7.69 (d,
J = 7.6Hz, 1H), 7.50-7.44 (m, 1H), 7.11 (m, 1H), 5.04 (s, 2H).
[0114] The following intermediates were made in a similar way:
5H-imidazo[2,1-a]isoindole-2-carbaldehyde
7-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
8-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
9-Fluoro-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
6-Methoxy-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
7-Methoxy-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
8-Methoxy-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
9-Methoxy-5H-imidazo[2,1-a]isoindole-2-carbaldehyde
5H-Imidazo[1',2':1,5]pyrrolo[3,4-b]pyridine-2-carbaldehyde (i.e. 6-aza-5H-imidazo[2,1-a]isoindole-2-carbaldehyde)
8H-3,6,8a-Triaza-cyclopenta[a]indene-2-carbaldehyde (i.e. 7-aza-5H-imidazo[2,1-a]isoindole-2-carbaldehyde)
8H-3,5,8a-Triaza-cyclopenta[a]indene-2-carbaldehyde (i.e. 8-aza-5H-imidazo[2,1-a]isoindole-2-carbaldehyde)
5H-Imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine-2-carbaldehyde (i.e. 9-aza-5H-imidazo[2,1-a]isoindole-2-carbaldehyde)
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-5H-imidazo[2,1-a]isoindole
[0115]

[0116] A solution of 2-chloromethyl-5,8-dimethyl-[1,2,4]triazolo[1,5-a]pyrazine (1.351 g,
6.87 mmol) and triphenylphosphine (1.80 g, 6.87 mmol) in acetonitrile 150 mL was heated
at reflux for 12 h. The solvents were removed
in vacuo and the residue slurried in ether, filtered and dried to yield (5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-ylmethyl)-triphenyl-phosphonium;
chloride as an off white solid (2.412 g, 74.9%). LC-MS:
m/
z = 423.2 ([M-Cl]
+),
tR = 0.86 minutes, method A.
[0117] A solution of 5H-Imidazo[2,1-a]isoindole-2-carbaldehyde (150 mg, 0.81 mmol) in dry
THF (5.3 mL) was added to (5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-ylmethyl)-triphenyl-phosphonium
chloride (374 mg, 0.81 mmol) under argon and 1,8-diazabicyclo [5.4.0]undec-7-ene (120
micro L, 0.81 mmol) was added. The reaction mixture was stirred at room temperature
for 12 hours after which it was evaporated onto silica gel (2 g). Silica gel chromatography
(gradient elution; A:B 100:0 to 0:100, where A is ethyl acetate and B is 10% MeOH
in ethyl acetate) afforded the title compound as a mixture of the cis and trans isomers
(139 mg, 52%). LC-MS:
m/
z = 329.3 (MH
+),
tR = 0.96 minutes.
[0118] The following intermediates were prepared in a similar manner:
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-6-fluoro-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-7-fluoro-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-8-fluoro-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-9-fluoro-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-6-methoxy-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-7-methoxy-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-8-methoxy-5H-imidazo[2,1-a]isoindole
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-9-methoxy-5H-imidazo[2,1-a]isoindole
2-[(E)-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-5H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine
2-[(E)-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-5H-imidazo[1',2':1,5]pyrrolo[3,4-b]pyridine
[0119] The invention disclosed herein is further illustrated by the following examples.
Example 1: 2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-5H-imidazo[2,1-a]isoindole
[0120]

[0121] A solution of 2-chloromethyl-5,8-dimethyl-[1,2,4]triazolo[1,5-a]pyrazine (1.351 g,
6.87 mmol) and triphenylphosphine (1.80 g, 6.87 mmol) in acetonitrile 150 mL was heated
at reflux for 12 h. The solvents were removed
in vacuo and the residue slurried in ether, filtered and dried to yield (5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-ylmethyl)-triphenyl-phosphonium;
chloride as an off white solid (2.412 g, 74.9%). LC-MS:
m/
z = 423.2 ([M-Cl]
+),
tR = 0.86 minutes, method A.
[0122] A solution of 5H-Imidazo[2,1-a]isoindole-2-carbaldehyde (150 mg, 0.81 mmol) in dry
THF (5.3 mL) was added to (5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-ylmethyl)-triphenyl-phosphonium
chloride (374 mg, 0.81 mmol) under argon and 1,8-diazabicyclo [5.4.0]undec-7-ene (120
micro L, 0.81 mmol) was added. The reaction mixture was stirred at room temperature
for 12 hours after which it was evaporated onto silica gel (2 g). Silica gel chromatography
(gradient elution; A:B 100:0 to 0:100, where A is ethyl acetate and B is 10% MeOH
in ethyl acetate) afforded the title compound as a mixture of the cis and trans isomers
(139 mg, 52%). LC-MS:
m/
z = 329.3 (MH
+),
tR = 0.96 minutes.
Example 2: Synthesis of 2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole
[0123]

[0124] To a solution of 2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-vinyl]-5H-imidazo[2,1-a]isoindole
(139 mg, 0.423 mmol) in methanol (100 mL) was added 10% palladium on carbon (27 mg).
A current of hydrogen gas was bubbled through, and the reaction was kept under an
atmosphere of hydrogen overnight with stirring. After filtration the organics were
evaporated onto silica gel (2 g). Chromatography (gradient elution; A:B 100:0 to 0:100,
where A is ethyl acetate and B is 10% MeOH in ethyl acetate) afforded the title compound
as a white solid (50.6 mg, 36%).
1H NMR (500 MHz, CDCl
3):
δ 7.86-7.82 (m, 2H), 7.46-7.42 (m, 2H), 7.33 (t,
J = 7.5 Hz, 1H), 7.02 (s, 1H), 4.84 (s, 2H), 3.44 (dd,
J = 8.9, 6.6 Hz, 2H), 3.33 (dd,
J = 8.9, 6.6 Hz, 2H), 2.91 (s, 3H), 2.73 (s, 3H). LC-MS:
m/
z = 331.0 (MH
+),
tR = 0.74 minutes.
Example 3: 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5,6-dihydro-imidazo[2,1-a]isoquinoline
[0125]

[0126] A solution of 2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5,6-dihydro-imidazo[2,1-a]isoquinoline
(210 mg, 0.61 mmol) in methanol:DCM (2:1, v/v, 30 mL) was passed through a H-Cube®
Continuous-flow Hydrogenation Reactor (ThalesNano) at a flow rate of 1 mL/min through
a small cartridge of 10% Pd/C (THS01111) with an internal temperature of 25°C and
1 bar of hydrogen pressure. Evaporation of the volatiles afforded the title compound
(75 mg, 19%).
1H NMR (600 MHz, CDCl
3): (
δ 8.02 (dd, J = 7.7, 1.0 Hz, 1H), 7.83 (s, 1H), 7.33 (ddd,
J = 7.7, 1.3, 0.7 Hz, 1H), 7.26 (td,
J = 7.4, 1.3 Hz, 1H), 7.21 (dd,
J = 7.4, 0.7 Hz, 1H), 6.73 (s, 1H), 4.10 (t,
J = 6.9 Hz, 2H), 3.41 (dd,
J = 9.6, 6.5 Hz, 2H), 3.28 (dd,
J = 9.6, 6.5 Hz, 2H), 3.13 (t,
J = 6.9 Hz, 2H), 2.90 (s, 3H), 2.72 (s, 3H). LC-MS:
m/
z = 345.1 (MH
+),
tR = 0.83 minutes
[0127] The Following compounds were prepared analogously:
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyridin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole,
1H NMR (600 MHz, DMSO): δ 7.67 (d, J = 7.5 Hz, 1H), 7.57 (d, J = 7.5 Hz, 1H), 7.44 (t, J = 7.5 Hz, 1H), 7.38 - 7.32 (m, 2H), 7.27 (s, 1H), 6.92 (d, J = 7.2 Hz, 1H), 4.99 (s, 2H), 3.23 - 3.16 (m, 2H), 3.09 (dd, J = 9.7, 6.3 Hz, 2H), 2.67 (s, 3H). LC-MS: m/z = 330.2 (MH+), tR = 0.91 minutes
2-[2-(5-Methyl-[1,2,4]triazolo[1,5-a]pyridin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole,
1H NMR (600 MHz, DMSO): 5 7.67 (d, J = 7.5 Hz, 1H), 7.63 (d, J = 8.8 Hz, 1H), 7.59-7.52 (m, 2H), 7.44 (t, J = 7.5 Hz, 1H), 7.35 (t, J = 7.5 Hz, 1H), 7.26 (s, 1H), 7.03 (d, J = 7.0 Hz, 1H), 4.98 (s, 2H), 3.20 (dd, J = 9.5, 6.4 Hz, 2H), 3.09 (dd, J = 9.5, 6.4 Hz, 2H), 2.72 (s, 3H). LC-MS: m/z = 315.7 (MH+), tR = 0.78 minutes
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-7-fluoro-5H-imidazo[2,1-a]isoindole,
1H NMR (600 MHz, CDCl3): δ 7.82 (d, J = 1.0 Hz, 1H), 7.76 (dd, J = 8.3, 5.0 Hz, 1H), 7.16 - 7.11 (m, 2H), 6.99 (s, 1H), 4.81 (s, 2H), 3.49 - 3.37
(m, 2H), 3.33-3.22 (m, 2H), 2.89 (s, 3H), 2.70 (s, 3H). LC-MS: m/z = 349.1 (MH+), tR = 0.80 minutes
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-8-fluoro-5H-imidazo[2,1-a]isoindole,
1H NMR (600 MHz, CDCl3): δ 7.82 (d, J = 0.8 Hz, 1H), 7.50 (dd, J = 8.3, 2.4 Hz, 1H), 7.37 (dd, J = 8.3, 4.6 Hz, 1H), 7.02-6.99 (m, 2H), 4.80 (s, 2H), 3.41 (dd, J = 9.0, 6.5 Hz, 2H), 3.31 (dd, J = 9.0, 6.5 Hz, 2H), 2.89 (s, 3H), 2.71 (s, 3H). LC-MS: m/z = 349.1 (MH+), tR = 0.80 minutes
2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-7-methoxy-5H-imidazo[2,1-a]isoindole,
1H NMR (600 MHz, CDCl3): δ 7.82 (d, J = 0.7 Hz, 1H), 7.73 (d, J = 8.4 Hz, 1H), 7.00 - 6.93 (m, 3H), 4.78 (s, 2H), 3.86 (s, 3H), 3.41 (dd, J = 9.0, 6.6 Hz, 2H), 3.29 (dd, J = 9.0, 6.6 Hz, 2H), 2.89 (s, 3H), 2.71 (s, 3H). LC-MS: m/z = 361.2 (MH+), tR = 0.87 minutes
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-7-methoxy-5H-imidazo[2,1-a]isoindole,
LC-MS: m/z = 361,2 (MH+). Rt = 0,87 min. ; method = 131
2-{2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindol-5-yl}-propan-2-ol,
LC-MS: m/z = 389,2 (MH+). Rt= 0,88 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-6-fluoro-5H-imidazo[2,1-a]isoindole,
LC-MS: m/z = 349,1 (MH+). Rt= 0,78 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-9-fluoro-5H-imidazo[2,1-a]isoindole,
LC-MS: m/z = 349,1 (MH+). Rt= 0,74 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-8-methoxy-5H-imidazo[2,1-a]isoindole,
LC-MS: m/z = 361,2 (MH+). Rt= 0,85 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-6-methoxy-5H-imidazo[2,1-a]isoindole,
LC-MS: m/z = 361,2 (MH+). Rt= 0,87 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-9-methoxy-5H-imidazo[2,1-a]isoindole,
LC-MS: m/z = 361,2 (MH+). Rt= 0,85 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[1',2':1,2]pyrrolo[3,4-b]pyridine,
LC-MS: m/z = 332,1 (MH+). Rt= 0,62 min. ; method = 131
2-[2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[1',2':1,5]pyrrolo[3,4-b]pyridine,
LC-MS: m/z = 332,2 (MH+). Rt= 0,48 min. ; method = 131
Example 4: Synthesis of 2-[-2-(5,8-Dimethyl-7-oxy-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole
[0128]

[0129] A solution of 2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole
(500 mg, 1.51 mmol) in AcOH (5 mL) was treated with 35% aqueous hydrogen peroxide
(1.3 mL, 15.1 mmol) and the solution stirred at 40°C for 12 h. The volatiles were
removed in vacuo and the crude oil dissolved in water (10 mL) and basified to pH 10
with 2N NaOH solution. The solids were filtered, washed with water and dried at 40°C
to yield the title compound as an off white solid (101 mg, 20%).
1H NMR (500 MHz, CDCl
3): δ 7.85 (d,
J = 7.6 Hz, 1H), 7.70 (s, 1H), 7.49 - 7.39 (m, 2H), 7.34 (t,
J = 7.5 Hz, 1H), 7.02 (s, 1H), 4.85 (s, 2H), 3.38 (dd,
J = 8.8, 6.1Hz, 2H), 3.34 - 3.23 (m, 2H), 2.80 (s, 3H), 2.70 (s, 3H). LC-MS:
m/
z = 346.9 (MH
+),
tR = 0.53 minutes
Example 5: Synthesis of {2-[2-(5H-lmidazo[2,1-a]isoindol-2-yl)-ethyl]-5-methyl-[1,2,4]triazolo[1,5-a]pyrazin-8-yl}-methanol
[0130]

[0131] A solution of 2-[-2-(5,8-Dimethyl-7-oxy-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole
(91 mg, 0.26 mmol) in DCM (5 mL) was treated with trifluoroacetic anhydride (93 µL,
0.66 mmol) and the solution stirred at room temperature for 2 h. The volatiles were
removed in vacuo and the residue dissolved in DCM (10 mL) and saturated sodium carbonate
solution (10 mL) was added. The mixture was stirred vigorously for 3 h. The phases
were separated and the aqueous phase extracted with DCM (2 x 20 mL). The combine organics
were washed with water, brineand dried over MgSO
4. After evaporation of the volatiles the residue was purified by prep LCMS to yield
the title compound as an off white solid (27 mg, 20%).
1H NMR (600 MHz, CDCl
3): δ 8.22 - 8.15 (m, 1H), 7.94 (s, 1H), 7.68 - 7.54 (m, 3H), 7.21 (s, 1H) 5.14 (s,
2H), 5.10 (s, 2H), 3.47 (bs, 4H), 2.75 (s, 3H), 2.66 (s, 1H). LC-MS:
m/
z = 346.9 (MH
+),
tR = 0.61 minutes
Example 6: 2-([1,2,4]Triazolo[1,5-a]pyridin-2-ylsulfanylmethyl)-5H-imidazo[2,1-a]isoindole
[0132]

[0133] An adaptation of the method described in
WO 96/01826 was used. Imidazole-1-carbothioic acid (2-imino-2H-pyridin-1-yl)-amide (200 mg, 1.37
mmol) and 2-Chloromethyl-5H-imidazo[2,1-a]isoindole (300 mg, 1.46 mmol) were dissolved
in 1-propanol (25 mL) and the mixture was heated to reflux for 2 hours. The solvent
was removed under reduced pressure and the residue dissolved in dichloromethane. The
solution was washed with water and the organic layer was dried over Na
2SO
4 and concentrated. The residue was purified by chromatography on silica gel to afford
the title compound (273 mg, 62 %) as a yellow solid. LC-MS:
m/
z = 321.1 (MH
+),
tR = 1.40 min, method B.
[0134] The following compounds of the invention were prepared analogously:
2-[(5,7-dimethyl-[1,2,4]triazolo[1,5-a]pyrimidin-2-yl)sulfanylmethyl]-5H-imidazo[2,1-a]isoindole;
LC-MS: m/z = 349.1 (MH+), tR = 1.59 min, method B.
2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-ylsulfanylmethyl)-5H-imidazo[2,1-a]isoindole
Example 7: Synthesis of 2-[-2-(5,8-Bis(trideuteromethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5,5-dideutero-5H-imidazo[2,1-a]isoindole
[0135]

[0136] To a solution of sodium (30 mg, 1.3 mmol) dissolved in deutero-methanol (MeOD-
d4, 4 mL) was added 2-[-2-(5,8-Dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole
(25 mg, 0.076 mmol) and the solution was stirred at RT for 48 h. The solvents were
removed in vacuo and the residue dissolved in DCM (10 mL), washed with saturated sodium
bicarbonate solution, brine and the organic layer separated. The organic layer was
dired (MgSO4), filtered and the volatiles removed in vacuo to yield the title compound
as an off white solid. (14 mg, 53%).
1H NMR (600 MHz, MeOD-
d4):
δ 7.76 (s, 1H), 7.61 (d,
J = 7.5 Hz, 1H), 7.41 (d,
J = 7.5 Hz, 1H), 7.32 (t,
J = 7.5 Hz, 1H), 7.25 (t,
J = 7.5 Hz, 1H), 7.05 (s, 1H), 3.26 (dd,
J = 7.7 Hz, 2H), 3.13 (dd, J = 7.7 Hz, 2H). LC-MS:
m/
z = 338.4 (MH
+),
tR = 0.71 minutes.
Pharmacological Testing
PDE10A enzyme
[0137] Active PDE10A enzyme is prepared in a number of ways for use in PDE assays (
Loughney, K. et al. Gene 1999, 234, 109-117;
Fujishige, K. et al. Eur J Biochem. 1999, 266, 1118-1127 and
Soderling, S. et al. Proc. Natl. Acad. Sci. 1999, 96, 7071-7076). PDE10A can be expressed as full-length proteins or as truncated proteins, as long
as they express the catalytic domain. PDE10A can be prepared in different cell types,
for example insect cells or E. coli. An example of a method to obtain catalytically
active PDE10A is as follows: The catalytic domain of human PDE10A (amino acids 440-779
from the sequence with accession number NP 006652) is amplified from total human brain
total RNA by standard RT-PCR and is cloned into the BamH1 and Xho1 sites of the pET28a
vector (Novagen). Expression in coli is performed according to standard protocols.
Briefly, the expression plasmids are transformed into the BL21 (DE3) E. coli strain,
and 50 mL cultures inoculated with the cells allowed to grow to an OD600 of 0.4-0.6
before protein expression is induced with 0.5mM IPTG. Following induction, the cells
are incubated overnight at room temperature, after which the cells are collected by
centrifugation. Cells expressing PDE10A are resuspended in 12 mL (50 mM TRIS-HCl-pH8.0,
1 mM MgCl
2 and protease inhibitors). The cells are lysed by sonication, and after all cells
are lysed, TritonX100 is added according to Novagen protocols. PDE10A is partially
purified on Q sepharose and the most active fractions were pooled.
PDE10A inhibition assay
[0138] A PDE10A assay may for example, be performed as follows: The assay is performed in
60 uL samples containing a fixed amount of the relevant PDE enzyme (sufficient to
convert 20-25% of the cyclic nucleotide substrate), a buffer (50 mM HEPES7.6; 10mM
MgCl
2; 0.02% Tween20), 0.1mg/ml BSA, 225 pCi of
3H-labelled cyclic nucleotide substrate, tritium labeled cAMP to a final concentration
of 5 nM and varying amounts of inhibitors. Reactions are initiated by addition of
the cyclic nucleotide substrate, and reactions are allowed to proceed for one hr at
room temperature before being terminated through mixing with 15 uL 8 mg/mL yttrium
silicate SPA beads (Amersham). The beads are allowed to settle for one hr in the dark
before the plates are counted in a Wallac 1450 Microbeta counter. The measured signal
can be converted to activity relative to an uninhibited control (100 %) and IC
50 values can be calculated using the Xlfit extension to EXCEL.
[0139] In the context of the present invention the assay was performed in 60 uL assay buffer
(50 mM HEPES pH 7.6; 10mM MgCl
2; 0.02% Tween20) containing enough PDE10A to convert 20-25% of 10 nM
3H-cAMP and varying amounts of inhibitors. Following a 1 hour incubation the reactions
were terminated by addition of 15 uL 8 mg/mL yttrium silicate SPA beads (Amersham).
The beads were allowed to settle for one hr in the dark before the plates were counted
in a Wallac 1450 Microbeta counter. IC
50 values were calculated by non linear regression using XLfit (IDBS).
[0140] Results of the experiments showed that the tested compounds of the invention inhibit
the PDE10A enzyme with IC
50 values below 10 nM.
Phencyclidine (PCP) induced hyperactivity
[0141] Male mice (NMRI, Charles River) weighing 20-25g are used. Eight mice are used in
each group receiving the test compound (5 mg/kg) plus PCP (2.3 mg/kg) including the
parallel control groups receiving the vehicle of the test compound plus PCP or vehicle
injections only. The injection volumen is 10 ml/kg. The experiment is made in normal
light conditions in an undisturbed room. The test substance is injected per oss 60
min before injection of PCP, which is administered subcutaneous.
[0142] Immediately after injection of PCP the mice are placed individually in special designed
test cage (20 cm x 32 cm). The activity is measured by 5X8 infrared light sources
and photocells spaced by 4 cm. The light beams cross the cage 1.8 cm above the bottom
of the cage. Recording of a motility count requires interruption of adjacent light
beams, thus avoiding counts induced by stationary movements of the mice.
[0143] Motility is recorded in 5 min intervals for a period of 1 hour. The drug effect is
calculated on the total counts during the 1 hour behavioral test period in the following
manner:
The mean motility induced by vehicle treatment in the absence of PCP is used as baseline.
The 100 per cent effect of PCP is accordingly calculated to be total motility counts
minus baseline. The response in groups receiving test compound is thus determined
by the total motility counts minus baseline, expressed in per cent of the similar
result recorded in the parallel PCP control group. The per cent responses are converted
to per cent inhibition.
[0144] Results of the experiments showed that the tested compound 2-[2-(5,8-dimethyl-[1,2,4]triazolo[1,5-a]pyrazin-2-yl)-ethyl]-5H-imidazo[2,1-a]isoindole
is an in vivo active compound that inhibits the PCP induced hyperactivity
ED50 = 0.2 mg/kg;
Inhibition is 100% at 5 mg/kg.