RU2824527C2 - Substituted tetrahydroisoquinoline derivative as positive allosteric modulator d1 - Google Patents

Abstract

FIELD: chemistry; pharmaceutics.

SUBSTANCE: invention relates to chemistry and pharmaceutics, specifically to a compound of formula (I) or a pharmaceutically acceptable salt thereof, a pharmaceutical composition having activity of a positive allosteric modulator D1, based on it, a method of treating and/or preventing cognitively related and negative symptoms of schizophrenia, mild cognitive impairment, impulsivity, Parkinson's disease and other movement disorders, dementia with Lewy bodies, Alzheimer's disease, for which the introduction of a positive allosteric modulator D1 is indicated, and a method of treating Parkinson's disease and other movement disorders, Alzheimer's disease or cognitively related and negative symptoms of schizophrenia, for which the administration of a positive allosteric modulator D1 is indicated, which include administering a compound of formula (I) or a pharmaceutically acceptable salt thereof in an effective amount.

EFFECT: use of the invention enables effective treatment of diseases for which the introduction of a positive allosteric modulator D1 is indicated.

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Description

The present invention relates to a tetrahydroisoquinoline derivative and its use in therapy. In particular, the present invention relates to a pharmacologically active substituted tetrahydroisoquinoline derivative.

This compound acts as a positive allosteric modulator of D1 and is therefore useful as a pharmaceutical agent for the treatment of diseases in which D1 receptors play a role.

Dopamine, a monoamine, acts on GPCRs (G protein-coupled receptors) of two families and modulates motor function, reward-related mechanisms, cognitive processes, and other physiological functions. In particular, dopamine acts on neurons through D1-like receptors, including dopamine receptors D1 and D5, which are mainly coupled to the G protein G _s , and therefore stimulate the production of cAMP (cyclic adenosine monophosphate) through D2-like receptors, which include receptors D2, D3, and D4, which are coupled to G proteins G _i/q and which suppress the production of cAMP. These receptors are widely expressed in different areas of the brain. In particular, D1 receptors are involved in many physiological functions and behavioral processes. For example, D1 receptors are involved in synaptic plasticity, cognitive function, and goal-directed motor functions, as well as reward-related processes. Due to their role in several physiological/neurological processes, D1 receptors have been implicated in a variety of disorders, including cognitive-related and negative symptoms of schizophrenia, cognitive impairment associated with classical antipsychotic drug treatment, impulsivity, attention deficit hyperactivity disorder (ADHD), Parkinson's disease and related movement disorders, dystonia, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, age-related cognitive decline, mild cognitive impairment (MCI), drug overuse addiction, sleep disorders, and apathy.

It has been shown that it is difficult to develop orally bioavailable small molecules targeting D1 receptors. D1 agonists developed to date are characterized by the presence of a pyrocatechol moiety and therefore their use in clinical practice is limited to invasive treatment. Ensuring sufficient selectivity has also proven difficult due to the high degree of homology of the ligand binding sites of dopamine receptor subtypes (e.g., dopamine D1 and D5 receptors). In addition, the use of D1 agonists is limited due to possible side effects, including dyskinesia and hypotension.

Therefore, it is necessary to develop new agents that can modulate D1 receptors.

There has been increasing interest in identifying allosteric modulators of GPCRs as tools for understanding the mechanism of receptor action and as potential therapeutic agents. GPCRs represent the largest family of cell surface receptors, and a large number of commercially available drugs directly activate or block signaling pathways mediated by these receptors. However, some GPCRs (e.g., peptide receptors) have proven difficult to design small molecules for or to achieve sufficient selectivity due to the high homology of ligand binding sites across receptor subtypes (e.g., dopamine receptors D1 and D5 or D2 and D3). Accordingly, the focus of much drug discovery has shifted toward identifying small molecules that act at sites distinct from those of the natural orthosteric agonist. Ligands that bind to these sites induce a conformational change in the GPCR and thereby allosterically modulate receptor function. Allosteric ligands have a variety of functions, including the ability to enhance (positive allosteric modulator, PAM) or attenuate (negative allosteric modulator, NAM) the effects of an endogenous ligand by affecting its affinity and/or potency. In addition to subtype selectivity, allosteric modulators may have other potential advantages for drug development, such as having no direct effects or potency of their own; only enhancing the effects of the native mediator at the site and time it is released; reducing the propensity to induce desensitization that occurs with chronic agonist exposure; and reducing the propensity to cause target-related side effects.

The compounds of the present invention enhance the action of D1 agonists or endogenous ligand on D1 receptors by an allosteric mechanism and are therefore positive allosteric modulators of D1 (PAM D1).

Therefore, the compound of the present invention, which is a D1 PAM, is useful for the treatment and/or prevention of diseases and disorders in which D1 receptors play a role. Such diseases include cognitive-related and negative symptoms of schizophrenia, neuroleptic drug-associated cognitive impairment, mild cognitive impairment (MCI), impulsivity, attention deficit hyperactivity disorder (ADHD), Parkinson's disease and other movement disorders, dystonia, Parkinson's disease dementia, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, drug or narcotic overuse addiction, sleep disorders, apathy, traumatic spinal cord injury or neuropathic pain.

International patent application WO 2013/051869 A1 discloses certain 3,4-dihydro-1H-isoquinolin-2-yl derivatives that are NK2 antagonists.

International patent application WO 2008/109336 A1 discloses certain tetrahydroisoquinoline compounds that are histamine H3 receptor modulators.

International patent application WO 2014/193781 A1 discloses certain 3,4-dihydroisoquinolin-2(1H)-yl derivatives useful for the treatment of cognitive impairment associated with Parkinson's disease or schizophrenia.

International patent application WO 2016/055479 discloses substituted 3,4-dihydroisoquinolin-2(1H)-yl derivatives and analogues thereof that may be useful for the treatment of diseases in which D1 receptors play a role.

International patent application WO 2019/204418 discloses certain pyrazotetrahydroisoquinoline derivatives that are positive allosteric modulators of D1 and may be useful for the treatment of Parkinson's disease and other movement disorders, Alzheimer's disease, schizophrenia and attention deficit hyperactivity disorder (ADHD).

However, there remains a need to develop active positive allosteric D1 modulators that exhibit a combination of favourable pharmacokinetic and pharmacodynamic properties while providing a reduction in side effects commonly associated with treatments involving selective D1 agonists, such as movement or cognitive impairment.

The present invention relates to 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]-1-[5-[2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinolin-2-yl]ethenone of formula (I),

or a pharmaceutically acceptable salt thereof.

The compound of the present invention falls within the generic scope of the co-pending international patent application WO 2016/055479. However, said application does not specifically disclose the compound of formula (I) above or a pharmaceutically acceptable salt thereof.

The present invention also relates to a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, intended for use in therapy.

Another object of the present invention is a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, intended for use in the treatment and/or prevention of diseases and/or disorders in which D1 receptors play a role.

Another object of the present invention is a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, intended for use in the treatment and/or prevention of cognitive-related and negative symptoms of schizophrenia, neuroleptic-associated cognitive impairment, mild cognitive impairment (MCI), impulsivity, attention deficit hyperactivity disorder (ADHD), Parkinson's disease and other movement disorders, dystonia, Parkinson's disease dementia, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, drug or narcotic overuse addiction, sleep disorders, apathy, traumatic spinal cord injury or neuropathic pain.

In a preferred embodiment of this object, the present invention relates to a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, for use in the treatment of Parkinson's disease and other movement disorders, Alzheimer's disease or cognitive and negative symptoms of schizophrenia.

Therefore, one preferred object of the present invention is a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, for use in the treatment of Parkinson's disease and other movement disorders.

Another object of the present invention is the use of a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, for the preparation of a medicament useful for the treatment and/or prevention of diseases and/or disorders in which D1 receptors play a role.

Another object of the present invention is the use of a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, for the preparation of a medicament useful for the treatment and/or prevention of cognitive-related and negative symptoms of schizophrenia, neuroleptic-associated cognitive impairment, mild cognitive impairment (MCI), impulsivity, attention deficit hyperactivity disorder (ADHD), Parkinson's disease and other movement disorders, dystonia, Parkinson's disease dementia, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, drug or narcotic overuse addiction, sleep disorders, apathy, traumatic spinal cord injury or neuropathic pain.

In a preferred embodiment of this aspect, the present invention relates to the use of a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, for the preparation of a medicament useful for the treatment of Parkinson's disease and other movement disorders, Alzheimer's disease or cognitive and negative symptoms of schizophrenia.

One preferred object of the present invention is the use of a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, for the preparation of a medicament useful for the treatment of Parkinson's disease and other movement disorders.

The present invention also relates to a method for the treatment and/or prevention of disorders for which administration of a positive allosteric modulator of D1 is indicated, which comprises administering to a patient in need of such treatment a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, in an effective amount.

Another object of the present invention is a method for the treatment and/or prevention of cognitive-related and negative symptoms of schizophrenia, neuroleptic-associated cognitive impairment, mild cognitive impairment (MCI), impulsivity, attention deficit hyperactivity disorder (ADHD), Parkinson's disease and other movement disorders, dystonia, Parkinson's disease dementia, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, drug or narcotic overuse addiction, sleep disorders, apathy, traumatic spinal cord injury or neuropathic pain, which comprises administering to a patient in need of such treatment a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof in an effective amount.

In a preferred embodiment of this aspect, the present invention relates to a method of treating Parkinson's disease and other movement disorders, Alzheimer's disease or cognitive and negative symptoms of schizophrenia, which comprises administering to a patient in need of such treatment a compound of formula (I) as defined above, or a pharmaceutically acceptable salt thereof, in an effective amount.

One preferred aspect of the present invention is a method of treating Parkinson's disease and other movement disorders which comprises administering to a patient in need of such treatment a compound of formula (I) as defined above or a pharmaceutically acceptable salt thereof in an effective amount.

The present invention includes salts of the compounds of formula (I) above. For use in medicine, salts of the compounds of formula (I) must be pharmaceutically acceptable salts. However, other salts can be used to prepare the compounds useful in the present invention or their pharmaceutically acceptable salts. Standard principles underlying the selection and preparation of pharmaceutically acceptable salts are described, for example, in the Handbook of Pharmaceutical Salts: Properties, Selection and Use, ed. P.H. Stahl & C.G. Wermuth, Wiley-VCH, 2002. Suitable pharmaceutically acceptable salts of the compound of formula (I) include acid addition salts, which can be prepared, for example, by mixing a solution of the compound of formula (I) with a solution of a pharmaceutically acceptable acid.

It should be understood that each individual atom contained in formula (I) or in the formulae presented hereinafter may in fact be contained in the form of any of its isotopes occurring in nature, with the most abundant isotope(s) being preferred. Thus, for example, each individual hydrogen atom contained in formula (I) or in the formulae presented hereinafter may be contained in the form of ¹ H, ² H (deuterium) or ³ H (tritium) atom, preferably as ¹ H or ² H. Similarly, for example, each individual carbon atom contained in formula (I) or in the formulae presented hereinafter may be contained in the form of ¹² C, ¹³ C or ¹⁴ C atom, preferably as ¹² C.

The present invention includes solvates of the compounds of formula (I) above. Such solvates can be obtained with common organic solvents or with water.

The present invention also includes co-crystals of the compounds of formula (I) above. The technical term "co-crystal" is used to describe the case where neutral molecular components are present in a crystalline compound in a certain stoichiometric ratio. The preparation of pharmaceutical co-crystals allows for modification of the crystalline form of the active pharmaceutical ingredient, which in turn can change its physicochemical characteristics without compromising its desired biological activity (see Pharmaceutical Salts and Co-crystals, ed. J. Wouters & L. Quere, RSC Publishing, 2012).

The compounds of the present invention may exist in various polymorphic forms. Although not explicitly indicated in the formula above, such forms are within the scope of the present invention.

The present invention also includes prodrug forms of the compounds of formula (I) and their various subclasses and subgroups.

The compound of formula (I) contains 2 asymmetric centers and can therefore exist as diastereoisomers. It should be understood that the present invention includes the use of all such diastereoisomers and mixtures thereof in any ratio. Therefore, formula (I) is intended to describe all individual stereoisomers and all possible mixtures thereof, unless otherwise stated or provided.

A preferred subject of the present invention is 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]-1-[(1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinolin-2-yl]ethenone of formula (IA),

or a pharmaceutically acceptable salt thereof.

Activity in any of the above therapeutic indications or disorders can, of course, be assessed by conducting appropriate clinical studies using methods known to those skilled in the art for the specific indication and/or by conducting general clinical studies.

For the treatment of diseases, the compound of formula (I) or its pharmaceutically acceptable salts can be used in an effective daily dose and administered in the form of a pharmaceutical composition.

Therefore, the present invention also relates to a pharmaceutical composition comprising a compound of formula (I) as presented above, or a pharmaceutically acceptable salt thereof, together with one or more pharmaceutically acceptable carriers.

To prepare the pharmaceutical composition of the present invention, one or more compounds of formula (I) or pharmaceutically acceptable salts thereof are intimately mixed with a pharmaceutical diluent or carrier according to conventional pharmaceutical compounding techniques known to skilled practitioners.

Suitable diluents and carriers may take a wide variety of forms depending on the desired route of administration, such as oral, rectal, parenteral or nasal.

Pharmaceutical compositions containing the compounds of the present invention can be administered, for example, orally, parenterally, i.e. intravenously, intramuscularly or subcutaneously, intrathecally, by inhalation or nasally.

Pharmaceutical compositions suitable for oral administration may be solid or liquid and may, for example, be in the form of tablets, pills, dragees, gelatin capsules, solutions, syrups, chewing gums, etc.

For this purpose, the active ingredient can be mixed with an inert diluent or a non-toxic pharmaceutically acceptable carrier such as starch or lactose. These pharmaceutical compositions may also optionally contain a binder such as microcrystalline cellulose, tragacanth gum or gelatin, a disintegrant such as alginic acid, a lubricant such as magnesium stearate, a glidant such as colloidal silicon dioxide, a sweetener such as sucrose or saccharin, or coloring agents, or a flavoring such as peppermint extract or methyl salicylate.

The present invention also includes compositions that can release the active substance in a controlled manner. Pharmaceutical compositions that can be used for parenteral administration are in conventional form, such as aqueous or oily solutions or suspensions, usually contained in ampoules, disposable syringes, glass or plastic vials or infusion containers.

In addition to the active ingredient, these solutions or suspensions may also optionally contain a sterile diluent such as water for injection, saline solution, oils, polyethylene glycols, glycerol, propylene glycol or other synthetic solvents, bactericides such as benzyl alcohol, antioxidants such as ascorbic acid or sodium bisulfite, chelating agents such as ethylenediaminetetraacetic acid, buffers such as acetates, citrates or phosphates, and agents for adjusting osmolality such as sodium chloride or dextrose.

These pharmaceutical forms are prepared according to methods that are routinely used by pharmacists.

The amount of the compound for use in the present invention required to prevent or treat a particular pathological condition will vary depending on the compound selected and the condition of the patient being treated. However, the daily dose may typically be in the range of 0.05 to 3000 mg, typically 0.5 to 1000 mg for compositions intended for parenteral administration.

The compound of the present invention or a pharmaceutically acceptable salt thereof may be administered alone (monotherapy) or in combination with L-dopa (combination therapy). When administered alone or in combination with fractions of the doses of L-dopa necessary to alleviate the motor deficit in patients, the compounds of formula (I) of the present invention or a pharmaceutically acceptable salt thereof may be useful for the treatment of dyskinesia associated with the administration of L-dopa. For example, it is believed that when the compound of formula (I) of the present invention is administered with fractions of the doses of L-dopa administered to a patient or is used alone to replace L-dopa, the compound of formula (I) of the present invention will be effective in eliminating the motor deficit and will not cause harmful dyskinesia. It is therefore believed that the compound of the present invention may be useful for the treatment of motor deficits and levodopa-induced dyskinesia (LID).

Therefore, one preferred object of the present invention is also a compound of formula (I), which is useful for the treatment of levodopa-induced dyskinesia (LID).

The compound of the present invention or a pharmaceutically acceptable salt thereof may be administered alone or in combination with another pharmaceutically active ingredient.

The compound of formula (I) can be prepared by a procedure comprising the reaction of an intermediate of formula (II) with an intermediate of formula (III).

The hydrochloride of intermediate (III) is then reacted with an intermediate of formula (II) in the presence of (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU) or another coupling reagent known to those skilled in the art in a suitable solvent, such as dimethylformamide, using an excess of a base, such as N,N-diisopropylethylamine.

Intermediates of formula (III) can be prepared by a procedure involving the reaction of an intermediate of formula (IV), in which Y is a halogen, such as bromine, with commercially available fluoroacetone.

The reaction is typically carried out by metal-halogen exchange, for example in the presence of n-BuLi in a suitable solvent, for example tetrahydrofuran, at low temperature using methods known to those skilled in the art.

When carrying out the above reactions, before introducing the intermediates of formula (III) and (IV) into the reaction with other reagents, the amino group contained therein is usually first protected with an appropriate protecting group, for example, a tert-butoxycarbonyl group, according to methods known to those skilled in the art.

Intermediates of formula (IIIa) can be prepared by a procedure involving the reaction of an intermediate of formula (V),

in which Y is as defined above in the present invention.

The reaction is typically carried out in the presence of a suitable reducing reagent, such as sodium borohydride, in a suitable solvent, such as ethanol, at low temperature, using methods known to those skilled in the art.

Intermediates of formula (V) can be prepared by a procedure involving the reaction of an intermediate of formula (VI),

in which Y is as defined above in the present invention.

The reaction is usually carried out in the presence of sulfuric acid in a suitable solvent, such as methanol, at room temperature.

The intermediate product of formula (VI) can be prepared by a procedure involving the reaction of a commercially available intermediate product (VII),

wherein Y is as defined above in the present invention.

The reaction is typically carried out in the presence of oxalyl chloride in a suitable solvent, such as dichloromethane, at low temperature, followed by the addition of iron(III) chloride at room temperature.

The intermediate product of formula (II) can be obtained by a multi-step procedure involving the reaction of intermediate products described by formula (VIII),

in which

R ¹ is hydrogen, -CH ₂ OH, -COOR ^a, or Y as defined above;

R ² stands for -COOR ^a ; and

R ^a denotes hydrogen or C ₁ -C ₆ -alkyl.

In the first step, an intermediate product of formula (VIII), in which R ¹ is hydrogen and R ^a is methyl, is reacted with an oxidizing reagent, such as m-chloroperbenzoic acid (m-CPBA), at low temperature in a suitable solvent, such as dichloromethane, to yield the corresponding N-oxide.

In the second step, the N-oxide obtained in the first step is reacted with phosphorus oxybromide to obtain the corresponding intermediate of formula (VIII), in which R ¹ is Y, as defined above in the present invention, and R ^a is methyl.

In the third step, the intermediate of formula (VIII) in which R ¹ is Y as defined above in the present invention is reacted with carbon monoxide in the presence of a base, such as N,N-diisopropylethylamine, in the presence of a transition metal catalyst, such as 1,4-bis(diphenylphosphino)butanepalladium(II) chloride, to obtain the corresponding intermediate of formula (VIII) in which R ¹ is -COOR ^a and R ^a is methyl. The reaction is typically carried out at high pressure and high temperature.

The ester group R ¹ contained in the last described intermediate product is then reduced to obtain the corresponding hydroxy group, then the ester group R ² is hydrolyzed to obtain the corresponding carboxy group and the intermediate product of formula (II) is obtained. The reaction is carried out according to methods well known to those skilled in the art and further described in the accompanying examples.

The intermediate product of formula (VIII), in which R ¹ is hydrogen and R ^a is methyl, can be prepared by procedures similar to those described in the accompanying examples or by standard procedures known to those skilled in the art.

If, in using any of the above-described procedures for preparing the compounds of the present invention, a mixture of products is formed, the desired product can be isolated therefrom at a suitable stage using conventional techniques such as preparative HPLC (high performance liquid chromatography) or column chromatography using, for example, silica and/or alumina together with a suitable solvent system.

If, when using the above-described methods for preparing the compounds of the present invention, a mixture of stereoisomers is formed, these isomers can be separated by conventional methods. In particular, when it is necessary to obtain a specific enantiomer of a compound of formula (I), it can be obtained from the corresponding mixture of enantiomers by any conventional method for separating enantiomers. Thus, for example, diastereoisomeric derivatives, for example salts, can be obtained by reacting a mixture of enantiomers of formula (I), for example a racemate, with an appropriate chiral compound, for example a chiral base. The diastereoisomers can then be separated by any conventional methods, for example by crystallization and the desired enantiomer can be isolated, for example by treatment with an acid, in the case where the diastereoisomer is a salt. In another separation method, the racemate of formula (I) can be separated using chiral HPLC. In addition, if desired, a specific enantiomer can be obtained by using a suitable chiral intermediate in one of the procedures described above. Alternatively, a specific enantiomer can be obtained by performing an enantiomerically specific enzymatic biological transformation, for example, hydrolysis of an ester using an esterase, followed by purification of only the enantiomerically pure hydrolytic acid from the unreacted ester antipode. If it is desired to obtain a specific geometric isomer of the present invention, chromatography, recrystallization, and other conventional separation techniques can also be used for intermediates or final products. Alternatively, an undesired enantiomer can be racemized in the presence of an acid or base using procedures known to those skilled in the art or using the procedures described in the accompanying examples to obtain the desired enantiomer.

During any of the above synthetic sequences, it may be necessary and/or desirable to protect sensitive or reactive groups contained in any of the molecules involved in the reactions. This can be accomplished by using conventional protecting groups such as those described in Protective Groups in Organic Chemistry, ed. J.F.W. McOmie, Plenum Press, 1973; and T.W. Greene & P.G.M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 3rd edition, 1999. The protecting groups can be removed at any suitable subsequent step by procedures known in the art.

The compounds of formula (I) proposed in the present invention do not activate the dopamine D1 receptor directly, but enhance the effect of D1 agonists or endogenous ligand on dopamine D1 receptors by an allosteric mechanism and therefore they are positive allosteric modulators of D1 (PAM D1).

Dopamine and other D1 agonists themselves directly activate the dopamine D1 receptor.

The studies are designed to examine the effects of the compounds of the present invention in the absence of dopamine (an "activation study") and in the presence of dopamine (an "enhancement study").

The activation assay measures the stimulation of cyclic adenosine monophosphate (cAMP) production using homogeneous time-resolved fluorescence (HTRF) imaging, with the maximal increase in cAMP produced by increasing concentrations of the endogenous agonist, dopamine, and defined as 100% activation.

According to the study, the compounds of formula (I) given in the examples do not exert significant direct agonist-like effects, since they provide activation that is less than 20% (of the maximum response to dopamine) at a concentration of 10 μM.

In the activity enhancement assay, the ability of compounds to increase the amount of cAMP produced at a low threshold concentration of dopamine is determined. This concentration of dopamine ([EC ₂₀ ]) is used to provide a stimulation equal to 20% of the maximal response (100%) obtained with increasing concentrations of dopamine. To determine this enhancement, compounds are incubated with increasing concentrations of dopamine [EC ₂₀ ] and the enhancement is defined as an increase in cAMP production and the concentration of compound that provides a 50% increase in cAMP concentration is determined.

According to the cAMP assay using OPRV, the compounds of formula (I) given in the examples have pEC ₅₀ values greater than about 6.5, indicating that they are positive allosteric modulators of D1.

It is known that inhibition of the GABA _A receptor is directly related to seizures and epilepsy. Therefore, it is necessary to develop compounds that are positive allosteric modulators of D1 and at the same time provide for minimization of such effects.

According to the GABA-A receptor inhibition assay described in the present invention, the compound of formula (I) provides a percentage inhibition of the GABA _A receptor of less than or equal to about 20% when the compound of formula (I) is tested at a concentration of 10 μM.

A difficulty that may arise in the development of compounds intended for use in therapy is the ability of certain compounds to inhibit CYP450 enzymes. Inhibition of such enzymes may affect the exposure of such compounds or other compounds that may be co-administered to the patient, likely altering their respective safety and efficacy. Therefore, it is necessary to develop compounds that minimize the likelihood of inhibition.

The ability of the compound of formula (I) according to the present invention to inhibit CYP450 is investigated by determining the possible decrease in CYP450 activities in human hepatocytes, which are incubated with the compounds according to the present invention at increasing concentrations.

In a CYP3A4 inhibition assay conducted at 1 and 20 μM concentrations according to the protocol described in the present invention, the compound of formula (I) of the present invention provides inhibition of less than about 40%, ideally less than about 30%.

When developing a compound for therapeutic use, it is important to have information about its elimination after it is administered to the body.

Clearance is a parameter that provides such information because it represents the volume of plasma (or blood) completely cleared of the compound of interest per unit time. It is usually expressed as ml/min/kg or l/h. It can then be compared with any physiological blood flow (e.g. hepatic blood flow) to determine whether clearance is low, intermediate or high.

If clearance is low, then depending on the volume of distribution, a low dose requirement and relatively long duration of action can be expected. If clearance is high, then also depending on the volume of distribution, a high dose requirement and relatively short duration of action can be expected.

Clearance is typically estimated according to the protocols described herein using incubation with hepatocytes and calculations by scaling the data, assuming that metabolism is the primary route of elimination. Intrinsic clearance calculated using hepatocytes is expressed as µl/min/10 ⁶ cells.

Preferably, when measured in a clearance assay as described herein, the compound of formula (I) as provided herein has a clearance of less than about 10 μl/min/10 ⁶ cells.

cAMP assay using OFRV

The specific conditions under which the compounds were tested are given below in the present invention.

a. Methods using D1-expressing cell culture

Cells were grown at 37°C in a humidified atmosphere containing 5% CO ₂ . Cells were grown in DMEM-F12+GlutaMAX™-I medium (GIBCO ^® , Invitrogen, Merelbeke, Belgium) containing 10% fetal bovine serum (BioWhittaker ^® , Lonza, Verviers, Belgium), 400 μg/ml geneticin (GIBCO ^® ), 100 IU/ml penicillin (IU = international units) and 100 IU/ml streptomycin (Pen-Strep solution, BioWhittaker ^® ). LMtk (Ltk-) mouse fibroblasts expressing the dopamine D1 receptor (BioSignal Inc, Montreal, Canada, now Perkin Elmer) were used and found to bind efficiently and produce robust functional responses (Watts et al, 1995).

b. cAMP study

The study of intracellular cyclic adenosine monophosphate (cAMP) concentration changes was determined using the CisBio FFRP dynamic cAMP assay kit (Codolet, France). The assay utilized a time-resolved homogeneous fluorescence assay and was based on the determination of competition between native cAMP produced by the cells and cAMP labeled with the d2 dye. Label binding was determined using cryptate-labeled cAMP antibodies. The effects of the compound alone (agonism) were determined by performing the assay in the absence of dopamine, whereas the effects of the compound as a positive allosteric modulator (PAM) were determined in the presence of dopamine, at a concentration equal to the EC ₂₀ . Cells (20,000 cells/well) were incubated in 384-well plates at room temperature for 1 h in a final volume of 20 μl in Hanks' Balanced Salt Solution (HBSS) (Lonza, containing calcium, magnesium and 20 mM HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer, pH 7.4) containing isobutylmethylxanthine (Sigma, final concentration: 0.1 mM), test compound at different concentrations (typically 10 ^-9.5 to 10 ^-4 ' ⁵ M) in the presence and absence of dopamine (final concentration: 1.1 nM). The reaction was then stopped and the cells were lysed by adding d2 detection reagent in lysis buffer (10 μl) and cryptate reagent in lysis buffer (10 μl) according to the manufacturer's instructions. The mixtures were then incubated at room temperature for an additional 60 min and the change in fluorescence emission signals in the RPB was determined according to the manufacturer's instructions using an Envision plate reader (Perkin Elmer, Zaventem, Belgium) under laser excitation. All incubations were performed in duplicate and the results were compared with the concentration-response relationship obtained for dopamine (10 ^-11 to 10 ^-6 M).

p. Analysis of results

The results were analyzed using Excel and PRISM (GraphPad Software) and _pEC50 and _Erel values were obtained using the 4-parameter logistic equation (DeLean et al, 1978), where _Erel is the approximated maximal response to the test compound after subtracting background, expressed as a percentage of the value obtained using dopamine, which is defined as 100%.

The pEC ₅₀ value of a compound is equal to - log 10 of the concentration of the compound that produces a 50% increase in cAMP concentration.

E _rel denotes the relative potency, defined as the maximum increase in activity, expressed as a percentage, provided by the compound compared to the maximum response obtained with increasing concentrations of dopamine (E _rel = 1 = maximum response to dopamine.

According to the study described in the present invention, the compound of formula (Ia) has a pEC ₅₀ value of about 6.9, and the compound of formula (Ib) has a pEC ₅₀ value of about 6.7.

The corresponding E _rel value possessed by the compound of formula (Ia) is approximately 64%, and the corresponding E _rel value possessed by the compound of formula (Ib) is approximately 61%.

Automated voltage-clamp studies using GABA _A receptor-containing cells

CHO-K1 cells stably expressing the α1, α2, and α2 subunits of the human GABA _A receptor were used. Cells were grown with trypsin and maintained in serum-free medium at room temperature. Cells were washed and resuspended in extracellular solution prior to analysis.

Potential clamp studies

Experiments using human GABA _A (α ₁ β ₂ γ ₂ ) channels were performed using an automated voltage-clamp assay (IonFlux™ HT). Compounds were assayed at 3 concentrations (0.1, 1 and 10 μM) using 3 to 4 cells. The external solution for recording GABA _A currents consisted of 137 mM sodium chloride, 4 mM potassium chloride, 1.8 mM calcium chloride, 1 mM magnesium chloride, 10 mM HEPES and 10 mM glucose. The external and internal solutions were titrated with NaOH or KOH and adjusted to a pH of 7.35 or 7.3, respectively. The internal pipetted solution contained 70 mM potassium fluoride, 60 mM potassium chloride, 70 mM sodium chloride, 5 mM HEPES, 5 mM EGTA (ethylene glycol tetraacetic acid), and 4 mM magnesium-ATP (adenosine triphosphate) complex. The final concentration of the solvent, DMSO, used to dilute the compounds was 0.33% in each well. Bicuculline (0.032 to 100 μM) was used as a positive control inhibitor. GABA (15 μM) was used as an agonist. All measurements were performed at a baseline potential of -60 mV.

The sequence of compound addition was as follows: GABA was added at a concentration corresponding to the _EC80 to determine the baseline response. Compound was treated at each concentration for 30 s, then treated with 15 μM GABA in the presence of compound for 2 s. The procedure was repeated using the next higher concentration of compound. The maximum inward current values were determined as a response to the addition of GABA in the presence of compound at one concentration. All results obtained for a compound were normalized to the baseline maximum current value obtained with treatment with 15 μM GABA for 2 s.

According to the above study, the compound of formula (Ia) at a concentration of 10 μM provides a percentage inhibition of the GABA _A receptor of approximately 13%.

According to the above study, the compound of formula (Ib) at a concentration of 10 μM provides a percentage inhibition of the GABA _A receptor of approximately 20%.

In vitro CYP3A4 inhibitory capacity study using frozen human microsomes

The objective of the study using human microsomes was to determine the inhibitory capacity of the compound of formula (I) by determining CYP3A4 activities after its co-incubation with midazolam, a specific CYP3A4 substrate.

For this purpose, frozen human microsomes (from pooled donors) were distributed into the wells of a 48-well collagen-coated plate such that the final concentration was 0.25 mg/mL. UCB compound was then added to the wells at 1 μM and 20 μM, in duplicate for each assay. After incubation for 30 min, midazolam was added at a concentration of 2.5 μM. After 15 min, an aliquot was removed and placed in the same volume of methanol containing the internal standard. The samples were centrifuged at 2500 rpm at 4°C for 20 min. An aliquot of the supernatant was diluted with deionized water, and 1-hydroxyimidazolam concentrations were determined by typical LC-MS/MS methods.

The concentration values were compared with the values obtained by incubation with midazolam at the same concentration, but without preliminary incubation with the UCB compound. The results are presented as % inhibition.

The compound of formula (Ia) of the present invention provides a percentage inhibition of CYP3A4 of approximately 28% at a concentration of 20 μM and approximately 20% at a concentration of 1 μM.

Azamulin study

Frozen human hepatocytes (mix of 20 donors, BSU lot from Celsis/IVT/Bioreclamation) were thawed according to the supplier's recommendations. Viability (selection with trypan blue dye) was >75%. Pre-incubation (250 μl of hepatocyte suspension at a concentration of 2 × 10 ⁶ hepatocytes/ml) was performed in Williams medium containing 2 mM glutamine and 15 mM HEPES in 48-well plates at +37°C in an incubator (5% CO ₂ ) with gentle shaking (vibrating shaker, Titramax 100, approximately 300 rpm) for 30 min. After preincubation, incubation was started by adding 250 μM culture medium (composition described above) containing UCB compound (1 μM) or midazolam (positive control) to the hepatocytes. Final concentrations of UCB compound in the incubation mixtures were 0.5 μM. Cell suspensions were quickly rehomogenized by pipetting twice. After incubation for 0, 30, 60, 120, 180, and 240 min, reactions were stopped by transferring 50 μL of the incubated mixtures to appropriate wells of a 96-well plate containing 50 μL of ice-cold acetonitrile supplemented with 1 μM ketoconazole as an internal standard. Before each sampling, incubated cells were re-homogenized by pipetting and releasing the sample twice.

To determine the concentration of the UCB compound, samples were analyzed using the LC-MS-MS bioanalytical method. The concentration-time dependence was approximated to determine the intrinsic clearance (Clint), expressed in μl/min/10 ⁶ cells.

When incubated with a suspension of human hepatocytes, the intrinsic clearance (Clint) of the compound of formula (Ia) according to the present invention is about 8.8 μl/min/10 ⁶ cells and the intrinsic clearance (Clint) of the compound of formula (Ib) is about 9.2 μl/min/10 ⁶ cells.

The following examples illustrate the preparation of compounds of formula (I) proposed in the present invention.

EXAMPLES

Abbreviations/Reusable Reagents

ACN: Acetonitrile

cAMP: cyclic adenosine monophosphate

Brine: a saturated aqueous solution of sodium chloride

nBu: n-butyl

tBu: tert-butyl

CHO: Chinese Hamster Ovary

m-CPBA: 3-chloroperbenzoic acid

CYP450: cytochromes P450

DCM: dichloromethane

DMF: N,N-dimethylformamide

DMSO: dimethyl sulfoxide

EC _20/50 : concentration that provides 20%/50% of the maximum response value

EGTA: egtazic acid (ethylene glycol tetraacetic acid)

E _rel : relative efficiency

ER ⁺ : electrospray ionization in positive ion mode

Et: ethyl

EtOH: ethanol

Et ₂ O: diethyl ether

EtOAc: ethyl acetate

GABA: γ-aminobutyric acid

h: hour(s)

HEPES: 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid

HPLC: High Performance Liquid Chromatography

HRTF: Homogeneous Time-Resolved Fluorescence

LCMS: liquid chromatography mass spectrometry

DAL: lithium diisopropylamide

MeOH: methanol

min: minute(s)

NMR: Nuclear Magnetic Resonance

iPrOH: isopropanol

CT: room temperature

SLC: supercritical liquid chromatography

TEA: triethylamine

THF: tetrahydrofuran

TLC: thin layer chromatography

Names according to IUPAC (International Union of Pure and Applied Chemistry) standards are obtained using Biovia Draw 16.1 software.

Analysis methods

All reactions involving air- or moisture-sensitive reagents are carried out under nitrogen or argon using dried solvents and glassware. Commercially available solvents and reagents are generally used without further purification, including anhydrous solvents when practical (usually Sure-Seal™ from Aldrich Chemical Company or AcroSeal™ from ACROS Organics). Reactions are typically monitored by thin-layer chromatography, HPLC, or mass spectrometry.

HPLC analyses were performed using an Agilent 1100 series HPLC system with a Waters XBridge MS C18, 5 µm, 150×4.6 mm column. The gradient mode starts from 100% solvent A (a mixture of water/ACN/ammonium formate solution of composition 85/5/10 (v/v/v)) to 100% solvent B (a mixture of water/ACN/ammonium formate solution of composition 5/85/10 (v/v/v) in 6 min, maintaining at 100% B for 5 min. The flow rate is set at 8 ml/min for 6 min, then increased to 3 ml/min in 2 min, maintaining at 3 ml/min for 3 min. A 1/25 split of the sample is used immediately before the IAP (atmospheric pressure ionization) source. Chromatography is carried out at 45 °C. Ammonium formate solution (pH ~ 8.5) is prepared by dissolving ammonium formate (630 mg) in water (1 L) with by adding 30% ammonium hydroxide solution (500 µl).

It should be obvious to one skilled in the art that different retention times can be obtained using different LC analytical conditions.

Mass spectrometric studies in LCMS mode are carried out as follows:

- To carry out elution in an alkaline medium during analysis, the following conditions are used:

A Waters QDA single quadrupole mass spectrometer is used for LCMS analysis. The spectrometer is equipped with an ESI (electrospray ionization) source and an Acquity Hclass UPLC with a diode array detector (200 to 400 nm). Data are collected in full scan MS mode from 70 to 800 m/z, in positive ion mode, and with alkaline elution. Reversed-phase separation is performed at 45°C using a Waters Acquity UPLC BEHC18, 1.7 μm (2.1 x 50 mm) alkaline elution column. Gradient elution is performed using a water/ACN/ammonium formate mixture (95/5/63 mg/L) (solvent A) and a ACN/water/ammonium formate mixture (95/5/63 mg/L) (solvent B). Injection volume: 1 µL. Full-flow mode in MS.

Alkaline program "4 min"

Alkaline environment program "10 min"

- To carry out elution in an acidic environment during analysis, the following conditions are used:

A Waters QDA single quadrupole mass spectrometer is used for LCMS analysis. The spectrometer is equipped with a PER source and an Acquity Hclass UPLC with a diode array detector (200 to 400 nm). Data are collected in full scan MS mode from 70 to 800 m/z, in positive ion mode and with acidic elution. Reversed phase separation is carried out at 45°C using a Waters Acquity UPLC HSS T3 1.8 μm (2.1 x 50 mm) column for acidic elution. Gradient elution is carried out using water/ACN/TFA (trifluoroacetic acid) (95/5/0.5 mL/L) (solvent A) and ACN (solvent B). Injection volume: 1 μL. Full flow MS mode.

Acidic environment program "4 min"

Acidic environment program "10 min"

Crude substances can be purified by normal phase chromatography, reversed phase chromatography (in acidic or basic medium), chiral separation, or recrystallization.

Conventional reversed-phase chromatography is performed using silica gel columns (100:200 mesh silica gel or Puriflash®-50SIHC-JP columns from Interchim).

Preparative reversed phase chromatography is carried out as follows:

- Purification by LCMS (alkaline medium, preparative LCMS)

LCMS purification is performed using a Waters SQD or QM triple quadrupole mass spectrometer. This spectrometer is equipped with a PER source and a Waters preparative LC four-component pump with a diode array detector (210 to 400 nm).

MS parameters: The voltage on the ESI capillary is 3 kV. The voltage on the cone and extractor is 10 V. The temperature of the source block is 120 °C. The desolvation temperature is 300 °C. The gas flow rate on the cone is 30 l/h (nitrogen). The flow rate of the desolvation gas is 650 l/h. Data collection is performed in the full scan mode in MS from 100 to 700 m/z, in the positive ion mode with elution in an acidic medium or in an alkaline medium.

LC parameters: Reversed-phase separation was carried out at RT using an XBridge prep OBD C18 column (5 μm, 30×50 mm) (for alkaline elution). Gradient elution was carried out using water (solvent A), ACN (solvent B), 8 g/L ammonium bicarbonate in water +500 μL/L 30% NH ₄ OH (solvent C) (pH~8.5). HPLC flow rate: 35 to 60 mL/min, injection volume: 1 mL. The split ratio for MS was set to +/- 1/6000.

Crude substances can be purified by normal phase chromatography, reversed phase chromatography (in acidic or basic medium), chiral separation, or recrystallization.

Before final analysis and biological testing of products, they are usually dried in a vacuum.

All NMR spectra were recorded at 250 MHz, 300 MHz, 400 MHz or 500 MHz.

1. Obtaining the intermediate product (II) - 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetic acid

1.1 Preparation of 3,5-dichloro-4-methylpyridine a2

A reactor was charged with DAL (1.86 L, 2 M solution in THF, 3.72 mol) and THF (5.0 L) under nitrogen atmosphere. At -20 °C, 3,5-dichloro-4-methylpyridine a1 (500 g, 3.38 mol) was added and the mixture was stirred at -10 °C for 30 min. The reaction mixture was cooled to -70 °C and methyl iodide (815 g, 5.74 mol) was added. The mixture was allowed to warm to room temperature and stirred for 4 h. This entire procedure was carried out simultaneously using 4 equal sized portions and they were processed together. The mixture was cooled to 0 °C and the reaction was quenched with water (5 L) and the mixture was stirred for 10 min. The aqueous phase was extracted with ethyl acetate (2 x 3 L) and the combined organic phase was washed twice with brine (10 L), dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The crude product was purified by recrystallization from ethanol (4 L) at -70°C to give 3,5-dichloro-4-methylpyridine a2 as a yellow solid (1.5 kg, 68.5% yield).

1.2. Preparation of methyl 2-(3,5-dichloro-4-pyridyl)acetate - intermediate product a3

3,5-Dichloro-4-methylpyridine a2 (375 g, 2.31 mol) and DMF (1.87 L) were placed in a reactor and the mixture was cooled to 15 °C. Under nitrogen atmosphere, potassium tert-butoxide (779 g, 6.94 mol) was added at 10-15 °C and the mixture was stirred at 15 °C for 30 min. Dimethyl carbonate (730 g, 8.10 mol) was added at 10-15 °C and the mixture was stirred at 30 °C for 4 h. This whole procedure was carried out simultaneously using 4 equal sized portions and they were processed together. The mixture was cooled to 0 °C and the reaction was quenched with water (10 L) and the mixture was stirred for 10 min. The reaction mixture was filtered and the filter cake was washed twice with ethyl acetate (2 L). The aqueous phase was extracted twice with ethyl acetate (3 L) and the combined organic phase was washed twice with brine (5 L), dried over anhydrous sodium sulfate, filtered and concentrated in vacuo to give methyl 2-(3,5-dichloro-4-pyridyl)acetate a3 as a black-brown liquid (1.3 kg, 63.8% yield), which was used in the next step without further purification.

1.3. Preparation of methyl 2-(3,5-dichloro-1-oxidopyridin-1-ium-4-yl)acetate - intermediate product a4

Methyl 2-(3,5-dichloro-4-pyridyl)acetate a3 (650 g, 2.95 mol) and dichloromethane (3.25 L) were placed in a reactor. Under nitrogen atmosphere at 0 °C, m-CPBA (1.27 kg, 5.91 mol, 80% purity) was added and the mixture was stirred at 25 °C for 5 h. This entire procedure was carried out simultaneously using 2 portions of the same size and they were processed together. The mixture was cooled to 0 °C and the reaction was quenched with water (4 L) and the mixture was stirred for 10 min. The reaction mixture was filtered and the filter cake was washed twice with dichloromethane (3 L). The aqueous phase was extracted twice with dichloromethane (2 L) and the combined organic phase _{was washed three times with saturated Na2S2O3 solution (} 15 L) and twice with brine (10 L), then dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The residue was purified by silica gel chromatography (petroleum ether:ethyl acetate, 20:1 to 1:1) to give methyl 2-(3,5-dichloro-1-oxidopyridin-1-ium-4-yl)acetate a4 as a yellow solid (900 g, 64.2% yield).

1.4. Preparation of methyl 2-(2-bromo-3,5-dichloro-4-pyridyl)acetate, intermediate product a5

Methyl 2-(3,5-dichloro-1-oxidopyridin-1-ium-4-yl)acetate a4 (900 g, 3.81 mol) and acetonitrile (8 L) are placed in a reactor at 20 °C. Under nitrogen atmosphere, phosphorus oxybromide (POBr ₃ , 1.09 kg, 3.81 mol) is added and the mixture is stirred at 25 °C for 12 h. This whole procedure is carried out simultaneously using another portion (quantity: 1.64 mol) and the two portions are processed together. The mixture is cooled to 0 °C and the reaction is quenched with water (3 L) and the mixture is stirred for 10 min. The aqueous phase is extracted twice with ethyl acetate (2 L). The combined organic phase is washed twice with brine (5 L), dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The residue was purified by chromatography on silica gel (petroleum ether:ethyl acetate, 50:1 to 1:1) to give methyl 2-(2-bromo-3,5-dichloro-4-pyridyl)acetate a5 as an off-white solid (503 g, 43% yield).

¹ H NMR (400 MHz, CDCl ₃ ) δ 8.32 (s, 1H), 4.07 (s, 2H), 3.75 (s, 3H)

1.5. Preparation of methyl 3,5-dichloro-4-(2-methoxy-2-oxoethyl)pyridine-2-carboxylate - intermediate product a6

To a solution of methyl 2-(2-bromo-3,5-dichloro-4-pyridyl)acetate a5 (3 g, 10.03 mmol) in methanol (60 ml) were added N,N-diisopropylethylamine (2.42 ml, 14.6 mmol) and 1,4-bis(diphenylphosphino)butanepalladium(II) chloride (91 mg, 0.15 mmol). The reactor was purged with nitrogen three times, then sealed (purged three times) with carbon monoxide at a pressure of 5 bar and the mixture was heated at 80 °C for 3 h. The reaction mixture was filtered at room temperature through celite and the solvent was removed under reduced pressure. The crude product was purified by column chromatography. (Biotage SNAP Ultra, 25 g, eluent: ethyl acetate:hexane, 1:1). The solvent was removed in vacuo to give 3,5-dichloro-4-(2-methoxy-2-oxoethyl)pyridine-2-carboxylate a6 as a yellow liquid (1.84 g, yield 66%).

LCMS (MH ⁺ ): 278.

¹ H NMR (400 MHz, DMSO-d ₆ ) δ 8.75 (s, 1H), 4.12 (s, 2H), 3.93 (s, 3H), 3.68 (s, 3H).

1.6. Preparation of methyl 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetate - intermediate product a7

To a solution of methyl 3,5-dichloro-4-(2-methoxy-2-oxoethyl)pyridine-2-carboxylate a6 (305 mg, 1.09 mmol) in THF (10 mL) at room temperature was added sodium borohydride (124 mg, 3.29 mmol) and the reaction mixture was stirred at room temperature for 18 h. The reaction mixture was filtered and the solvent was removed in vacuo. The crude product was purified by column chromatography (Biotage SNAP Ultra, 25 g, eluent: dichloromethane:methanol, from 100:0 to 90:10). The solvent was removed in vacuo and methyl 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetate a7 was obtained as a solid (139 mg, yield 50%).

LCMS (MH ⁺ ): 250.

^1H NMR (400 MHz, CDCl ₃ ) δ 8.51 (s, 1H), 4.78 (s, 2H), 4.04 (s, 2H), 3.74 (s, 3H).

The signal of the proton contained in OH is absent.

1.7. Preparation of intermediate product (II) - 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetic acid

To a solution of methyl 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetate a7 (98.1 g, 392 mmol) in a mixture of THF (1.1 L) and water (110 mL) was added lithium hydroxide monohydrate (25.2 g, 589 mmol). The resulting mixture was stirred at room temperature for 18 h, then concentrated in vacuo. The residue was azeotropically distilled with toluene (3×250 mL) to give 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetic acid (II) as a free-flowing, almost white powder (92.6 g, 100% yield). The product was used in the next step without further purification.

¹ H NMR (400 MHz, DMSO-d ₆ ) δ 8.54 (s, 1H), 4.62 (s, 2H), 2.46 (s, 2H). Signals of the protons contained in two OH are absent.

2. Obtaining the intermediate product (III)

Preparation of (1R)-1-fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(R,S) and (1S)-1-fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(S,S)

2.1. Preparation of intermediate product (VI) - 7-bromo-10b-methyl-6,10b-dihydro-5H-[1,3]oxazolo[2,3-a]isoquinoline-2,3-dione a9

To a solution of N-[2-(2-bromophenyl)ethyl]acetamide a8 (commercially available, 106.5 g, 439.8 mmol) in DCM (1.5 L) at 0 °C was added dropwise oxalyl chloride (72 mL, 838.7 mmol). The mixture was stirred at 0 °C for 2 h, then allowed to warm to RT and stirred for 3 h. The reaction mixture was then cooled to 0 °C and iron(III) chloride (86 g, 530.2 mmol) was added in 2 portions. The reaction mixture was allowed to warm to RT, stirred at RT overnight, diluted with DCM (2.5 L) and then quenched at 0 °C with 12 M ammonia (200 mL). The organic layer _was dried over _Na2SO4 , filtered and concentrated in vacuo to give 108 g of 7-bromo-10b-methyl-6,10b-dihydro-5H-[1,3]oxazolo[2,3-a]isoquinoline-2,3-dione a9 as a brown solid, which was used in the next step without any further purification.

Yield (crude compound): 83%.

LCMS (ER ⁺ ): 296/298 (M+H) ⁺ .

2.2. Preparation of intermediate product (V) - 5-bromo-1-methyl-3,4-dihydroisoquinoline a10

To a suspension of 7-bromo-10b-methyl-6,10b-dihydro-5H-[1,3]oxazolo[2,3-a]isoquinoline-2,3-dione a9 (108 g, 364.72 mmol) in MeOH (1.5 L) at RT was added sulfuric acid (75 mL) dropwise. The reaction mixture was stirred at 65 °C overnight and then quenched with 15 M ammonia (300 mL) at 0 °C. The mixture was concentrated in vacuo and water (300 mL) was added. The aqueous layer was extracted six times with DCM (1 L). The organic layer was dried over _MgSO4 , filtered and concentrated in vacuo to give 86.44 g of 5-bromo-1-methyl-3,4-dihydroisoquinoline a10 as a brown solid, which was used in the next step without any further purification. Yield (crude compound): quantitative.

HPLC (alkaline medium): RT (retention time) 4.75 min, purity 87%.

2.3. Preparation of intermediate product (IV) - 5-bromo-1-methyl-1,2,3,4-tetrahydroisoquinoline a11

To a solution of 5-bromo-1-methyl-3,4-dihydroisoquinoline a10 (86.44 g, 385.9 mmol) in EtOH (2 L) at 0 °C was added sodium borohydride (13.2 g, 349 mmol) in portions (13 × 1 g). The mixture was stirred at 0 °C for 2 h, then 5 N aqueous HCl (250 mL) was added at 0 °C. The reaction mixture was stirred at RT overnight, then the EtOH was removed in vacuo. DCM (1 L) was added and the reaction was quenched at 0 °C with 6 M ammonia (400 mL). The organic layer was extracted twice with DCM (500 mL), dried over MgSO ₄ , filtered and concentrated in vacuo to give 83 g of 5-bromo-1-methyl-1,2,3,4-tetrahydroisoquinoline a11 as a brown solid, which was used in the next step without any further purification. Yield (crude compound): 95%.

HPLC (alkaline medium): RT 4.53 min, purity 80%.

2.4. Preparation of tert-butyl 5-bromo-1-methyl-3,4-dihydroisoquinoline-2(1H)-carboxylate - intermediates a12, a12-S and a12-R

To a solution of 5-bromo-1-methyl-1,2,3,4-tetrahydroisoquinoline a11 (78 g, 345 mmol) in DCM (1 L) at 0 °C was added TEA (160 mL, 1136 mmol). Then a solution of di-tert-butyl dicarbonate (65 g, 294.8 mmol) in DCM (250 mL) was added dropwise at 0 °C. The reaction mixture was stirred at RT overnight and quenched with water (100 mL). The organic layer was dried over MgSO ₄ , filtered and concentrated in vacuo. The residue was triturated twice with MeOH/n-hexanes (1:2, 450 mL) to give 63 g of tert-butyl 5-bromo-1-methyl-3,4-dihydroisoquinoline-2(1H)-carboxylate a12 (yield: 56%, HPLC (alkaline medium): VT 6.59 min, purity 98%) as a white solid. Chiral separation (NLC, Whelko 01(R,R), 50×227 mm, 360 mL/min, 220 nm, 25°C, eluent: from 20% iPrOH) of the racemate of tert-butyl 5-bromo-1-methyl-3,4-dihydroisoquinoline-2(1H)-carboxylate a12 gave:

- 25.1 g of tert-butyl (1S)-5-bromo-1-methyl-3,4-dihydroisoquinoline-2(1H)-carboxylate a12-S as a solid.

Yield: 22%.

HPLC (alkaline medium): RT 6.59 min, purity 91%.

Chiral analysis (LC, Whelko-01 (R,R), 250×4.6 mm, 1 ml/min, 220 nm, 30°C, eluent: iPrOH/n-heptane/DEA (diethylamine), 50/50/ 0.1): RT 4.86 min, EI (enantiomeric excess) 97.7%.

- 29.3 g of tert-butyl (1R)-5-bromo-1-methyl-3,4-dihydroisoquinoline-2(1H)-carboxylate a12-R as a solid.

Yield: 26%.

HPLC (alkaline medium): RT 6.59 min, purity 98%.

Chiral analysis (LC, Whelko-01 (R,R), 250×4.6 mm, 1 ml/min, 220 nm, 30°C, eluent: iPrOH/n-heptane/DEA, 50/50/0.1 ): RT 5.62 min, EI 92.4%.

2.5. Preparation of tert-butyl (1S)-5-[(1R)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate - intermediate product a13-(S,R) and tert-butyl (1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate - intermediate product a13-(S,S)

Tert-Butyl (1S)-5-bromo-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate a12-S (7 g, 21.45 mmol) was dissolved in dry tetrahydrofuran (107 mL) at -78 °C. n-BuLi (32.93 mmol) was added dropwise and the mixture was stirred at -78 °C for 10 min. Fluoroacetone (4.78 mL, 64.2 mmol) was added and the mixture was stirred at RT for 1 h. The reaction was quenched with 1 N aqueous HCl (350 mL) and then the mixture was extracted three times with dichloromethane. The organic layer was dried over MgSO ₄ , filtered and concentrated in vacuo. The residue was purified by reverse phase chromatography (alkaline medium, standard LC). Chiral separation (LC, Chiralpak 1C, 80×380 mm, 300 ml/min, 220 nm, 30°C, eluent: 10% iPrOH in heptane) gives:

- 1.137 g of tert-butyl (1S)-5-[(1R)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate a13-(S,R) as a beige solid.

Output: 16%

LCMS (ER ⁺ ): 268.0 (M-tBu+H) ⁺ .

Chiral analysis (LC, Whelko-01 (R,R), 150×4.6 mm, 1.5 ml/min, 220 nm, 30°C, eluent: iPrOH/n-heptane/DEA, 10/90/0 ,1): RT 2.37 min, EI 100%.

- 1.074 g of tert-butyl (1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate a13-(S,S) as a beige solid.

Yield: 15%.

LCMS (ER ⁺ ): 268.0 (M-tBu+H) ⁺ .

Chiral analysis (LC, Whelko-01 (R,R), 150×4.6 mm, 1.5 ml/min, 220 nm, 30°C, eluent: iPrOH/n-heptane/DEA, 10/90/0 ,1): RT 2.72 min, EI 100%.

2.6. Preparation of (1R)-1-fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(R,S) and (1S)-1-fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride - intermediate product a14-(S,S)

tert-Butyl (1S)-5-[(1R)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate a13-(S,R) (1.137 g, 3.516 mmol) was dissolved at RT in dioxane (18 mL). 4 N HCl in dioxane (8.8 mL, 35 mmol) was added. The mixture was stirred at RT overnight. The reaction mixture was concentrated in vacuo to give 950 mg of (1R)-1-fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(R,S) as a beige solid.

Yield (of crude compound): quantitative. LCMS (ER ⁺ ): 224.0 (M+H) ⁺ .

(1S)-1-Fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(S,S)

Compound a14-(S,S) can be synthesized by the same method using tert-butyl (1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinoline-2-carboxylate a13-(S,S) as the starting material.

Yield (crude compound): quantitative.

LCMS (ER ⁺ ): 224 (M+H) ⁺ .

3. Obtaining a compound of formula (I)

3.1. Preparation of a compound of formula (Ia) - 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]-1-[(1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinolin-2-yl]ethanone

To a solution of 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]acetic acid (II) (112 mg, 0.476 mmol) and (2S)-1-fluoro-2-[(1S)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(S,S) (136 mg, 0.524 mmol) in DMF (6 mL) was added (2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU, 217 mg, 0.571 mmol). Then N,N-diisopropylethylamine (0.24 mL, 1.43 mmol) was added at room temperature and the mixture was stirred for 2 h. The reaction was quenched with water and The mixture was extracted twice with ethyl acetate. The combined organic layers were dried over MgSO ₄ , filtered and the solvent removed in vacuo to give the crude product. The crude product was purified by reverse phase chromatography (basic medium) and the solvent removed in vacuo to give 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]-1-[(1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinolin-2-yl]ethanone 1 (116 mg, yield 55%) as a solid.

LCMS: 441(MH ⁺ ).

¹ H NMR (400 MHz, DMSO-d ₆ ) δ 8.59 (2s, 1H, rotational isomers), 7.37-7.09 (m, 3H), 5.48 (m, 1H), 5.34 (m, 2H), 4.72-4.53 (m, 3H), 4.53-4.25 (m, 1.3H), 4.25-4.03 (m, 1.7H), 4.02-3.69 (m, 2H), 3.48 (m, 0.7H), 3.38-3.33 (m, 0.3H partially masked by the signal of water, 3.31-3.07 (m, 1H), 1.60 (d, J=6.7 Hz, 1H), 1.53 (m, 3H), 1.37 (d, J=6.7 Hz, 2H).

3.2. Preparation of a compound of formula (Ib) - 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]-1-[(1S)-5-[(1R)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinolin-2-yl]ethanone

The desired compound is obtained in accordance with a procedure similar to that described for the preparation of the compound of formula (1a), using (2S)-1-fluoro-2-[(1R)-1-methyl-1,2,3,4-tetrahydroisoquinolin-5-yl]propan-2-ol hydrochloride a14-(S,R) as the starting material.

LCMS: 441(MH ⁺ ).

¹ H NMR (400 MHz, DMSO-d ₆ ) δ 8.58 (2s, 1H, 2 rotational isomers), 7.42-7.07 (m, 4H), 5.47 (s, SH, rotational isomers), 5.41-5.24 (m, 2H), 4.85-4.66 (m, 1H), 4.57-4.24 (m, 2H), 4.09 (s, 3H), 4.01-3.70 (m, 2H), 3.58-3.19 (m, 1H partially masked by the signal of water, 1.59 (d, J=6.7 Hz, 1H), 1.53 (m, 3H), 1.36 (dd, J=6.8, 2.0 Hz, 2H).

Claims (11)

1. A compound of formula (I) or a pharmaceutically acceptable salt thereof, . 2. A compound of formula (I) according to claim 1, which is 2-[3,5-dichloro-2-(hydroxymethyl)-4-pyridyl]-1-[(1S)-5-[(1S)-2-fluoro-1-hydroxy-1-methylethyl]-1-methyl-3,4-dihydro-1H-isoquinolin-2-yl]ethenone and is described by formula (IA) . 3. A compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof for use in therapy. 4. A compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof for use in the treatment and/or prevention of diseases and/or disorders in which D1 receptors play a role. 5. A compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof for use in the treatment and/or prevention of cognitive-related and negative symptoms of schizophrenia, neuroleptic-associated cognitive impairment, mild cognitive impairment (MCI), impulsivity, attention deficit hyperactivity disorder (ADHD), Parkinson's disease and other movement disorders, dystonia, dementia in Parkinson's disease, Huntington's disease, dementia with Lewy bodies, Alzheimer's disease, drug or narcotic overuse addiction, sleep disorders, apathy, traumatic spinal cord injury or neuropathic pain. 6. A compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof for use in the treatment of Parkinson's disease and other movement disorders, Alzheimer's disease or cognitive and negative symptoms of schizophrenia. 7. A pharmaceutical composition having the activity of a positive allosteric D1 modulator, containing an effective amount of a compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof together with a pharmaceutically acceptable carrier. 8. A method for treating and/or preventing cognitive-related and negative symptoms of schizophrenia, mild cognitive impairment (MCI), impulsivity, Parkinson's disease and other movement disorders, dementia with Lewy bodies, Alzheimer's disease, for which administration of a positive allosteric modulator of D1 is indicated, which comprises administering to a patient in need of such treatment a compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof in an effective amount. 9. A method for treating Parkinson's disease and other movement disorders, Alzheimer's disease or cognitive and negative symptoms of schizophrenia for which administration of a positive allosteric modulator of D1 is indicated, which comprises administering to a patient in need of such treatment a compound of formula (I) according to claim 1 or a pharmaceutically acceptable salt thereof in an effective amount.