ES2360150A1 - 1,8-naphthyridine-derived compounds and the use thereof in the treatment of neurodegenerative diseases - Google Patents

Abstract

1,8-Naphthyridine-derived compounds, the method for the production thereof and the use thereof as agents in the treatment of diseases of the central nervous system caused by a series of processes included in that which is generically known as neurodegeneration. Said diseases may be selected from the list that includes Alzheimer's disease, Parkinson's disease and Huntington's disease.

Description

Compounds derived from 1,8-naphthyridines and their use in the treatment of neurodegenerative diseases.

The present invention relates to compounds of general formula (I). The invention also relates to its obtaining procedure and its use as agents for treatment of diseases of the central nervous system caused by a series of processes included in what is generically called neurodegeneration The present invention can be framed in the pharmaceutical industry field.

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Prior art

The progressive aging of the population world brings with it the unwanted consequence of an increase in neurodegenerative diseases and senile dementias. Among these, the Alzheimer's disease, EA hereafter, is the disease most common neurodegenerative, responsible for approximately two thirds of total cases of dementia (varying between 42 and 81% according to different studies), with a prevalence closely related to age, which approaches 50% in the population over 85 years of age, and which affects women more than men.

Several biochemical processes are affected in the brains of AD patients: abnormal metabolism and aggregation of the amyloid protein, hyperphosphorylation of the tau protein, uncontrolled presence of oxidizing species, alterations of calcium ion homeostasis (Ca2 +) hereinafter), neuronal loss, problems in cholinergic neurotransmission, etc., in the brains of AD patients. Undoubtedly, an improvement of any of these pathologies separately would be a correct, if incomplete, approach to the treatment of the disease. Currently, the drugs used for the treatment of AD are agents that improve cholinergic neurotransmission, capable of relieving cognitive and memory deficits associated with AD, although only temporarily ( Arch. Gerontol. Geriatr. Suppl . 2004 , 9 , 297-307).

Given this situation, it is obvious the convenience of having drugs capable of acting in the early stages of the disease or, better yet, producing a protective activity in the initial phase of the disease, in the ideal case of having a system of adequate early diagnosis ( Ann. Neurol . 2007 , 61 , 120-129), and that they are capable of restoring or, at least, maintaining the physiological processes affected in neurodegenerative diseases at the closest possible levels to functional normality.

Studies carried out in both animal and human models show that the loss of balance between the oxidizing species generated by brain metabolism and antioxidant protective mechanisms produces so-called oxidative stress, when these defensive systems decrease their effectiveness and are overwhelmed. This oxidative stress increases with age and is among the first causes of the pathogenesis of AD ( Neurobiol. Aging 2007 , 28 , 1009-1014) possibly associated with dysfunctions of neuronal mitochondria. Likewise, it is known that products with antioxidant properties are capable of preventing apoptosis induced by amyloid peptide, as well as alterations of Ca2 + homeostasis in cortical neuron cultures ( Life Sci . 2000 , 66 ,
1879-1892).

On the other hand, hyperphosphorylation of the tau protein, associated with microtubule stability cell, leads to the formation of neurofibrillar clews in the inside of neurons that reflect the destruction of microtubules and neurofilaments, which eventually causes damage and neuronal death

On the other hand, some 1,8-naphthyridine derivatives have been described with neuroprotective activity (José Marco-Contelles et al ., Bioorqanic & Medicinal Chemistry 14 (2006) 8176-8185; Rafael León, et al ., Bioorqanic & Medicinal Chemistry 16 (2008) 7759-7769).

Description of the invention

The present invention is related to the ability of cholinesterase enzyme inhibitors to exert symptomatic improvements in Alzheimer's patients, through a mechanism of action that would not only imply the inhibition of this type of enzymes, but would additionally be able to lead to carry out other non-cholinergic activities, showing globally a neuroprotective profile of stimulus sensitive neurons triggered by the neurodegenerative process. These effects have observed in the family of compounds described herein invention.

More specifically, the present invention is refers to a family of compounds with the characteristic structural of being derived from the heterocyclic system 1,8-naphthyridine, which have properties Pharmacological potentially useful for the treatment of neurodegenerative diseases such as AD.

In the pharmacological studies that have been submitted, the compounds of the present invention have shown a series of potentially very useful activities in the treatment of neurodegenerative diseases, notwithstanding that in studies deeper, new biological properties of possible interest The activities studied, and that have shown Positive results have been:

- Enzyme inhibition acetylcholinesterase

- Enzyme inhibition butyrylcholinesterase.

- Neuroprotective effect on a line of neuroblastoma subjected to oxidative stress.

- Neuroprotective effect on a line of neuroblastoma undergoing hyperphosphorylation of the tau protein.

As described is the state of the art prior to the present invention, and there is an increasing number of experimental evidence, the presence of oxidizing species by above physiologically acceptable levels, the so-called stress oxidative, is at the origin of AD, and in turn is strongly related to uncontrolled ion inputs Ca 2+.

Therefore, a first aspect of the present invention refers to a compound of general formula (I) (from hence compounds of the invention):

2

where:

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R_ {1} and R2_ are groups same or different and each one is selected independently of a (C 1 -C 10) alkyl group; Y

n

is an integer from 0 to 5, and represents the number of additional carbon atoms to close the cycloalkane fused to the 1,8-naphthyridine heterocycle. Preferably n is 0, 1, 2 or 3.

By "compound of the invention" also refers in the present invention to any of its derivatives, isomers, pharmaceutically acceptable salt and / or solvate thereof.

The term "alkyl" refers to the present invention to aliphatic, linear or branched chains, which they have 1 to 10 carbon atoms, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, tert-butyl, sec-butyl, n-pentyl, n-hexyl, etc. Preferably the alkyl group It has between 1 and 6 carbon atoms. Alkyl radicals (R1) and / or R2) may be optionally substituted by one or more substituents such as a cycloalkyl, aryl, heteroaryl, alkoxy, halogen, haloalkyl, nitro, amino, aminoalkyl, aminocycloalkyl, ammoniumalkyl, ammoniumcycloalkyl or, in general, any substituent located in any position.

In a preferred embodiment of the present invention, R1 is methyl or ethyl. In another preferred embodiment, R2 is methyl.

In another more preferred embodiment, the compound of the invention is selected from the list comprising:

methyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo [ b ] [1,8] naphthyridine-3-carboxylate,

ethyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo [ b ] [1,8] naphthyridine-3-carboxylate,

• methyl 5-amino-2-methyl-7,8-dihydro-6 H -cyclopenta [ b ] [1,8] naphthyridine-3-carboxylate,

• 5-amino-2-methyl-7,8-dihydro-6 H -cyclopenta [ b ] [1,8] naphthyridine-3-carboxylic acid ethyl ester,

• methyl 5-amino-2-methyl-7,8,9,10-tetrahydro-6 H -cyclohepta [ b ] [1,8] naphthyridine-3-carboxylate,

• 5-amino-2-methyl-7,8,9,10-tetrahydro-6 H -cyclohepta [ b ] [1,8] naphthyridine-3-carboxylic acid ethyl ester,

• methyl 5-amino-2-methyl-6,7,8,9,10,11-hexahydrocycloocta [ b ] [1,8] naphthyridine-3-carboxylate, and

• ethyl 5-amino-2-methyl-6,7,8,9,10,11-hexahydrocycloocta [ b ] [1,8] naphthyridine-3-carboxylate.

The compounds of the present invention of formula (I) can be obtained or produced by a route synthetic chemistry or obtained from a natural matter of different origin. Another aspect of the present invention relates to a process for obtaining the compounds of the invention of formula (I), or an isomer, pharmaceutically acceptable salt and / or solvate thereof, characterized in that it comprises the following stages:

a) reaction of an alkyl acylacetate of the formula (II),

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in which R_ {1} and R2_ represent the substituents indicated above when describing the general formula (I), under substitution conditions with a dimethylformamide diaalkylacetal. This reaction would result in a acceptor Michael substituted in beta position with a group dimethylamino, which, by reaction with cyanoacetamide in basic conditions with evolution of dimethylamine and subsequent 6-exo-trig cycling, yields the corresponding 2-pyridone (III).

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b) nucleophilic substitution on the 2-pyridone (III) by excess oxychloride of phosphorus to get pyridine (IV);

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c) nucleophilic substitution on this pyridine (IV) to incorporate at the position of the Cl atom an amine, reaction that can be done by bubbling ammonia, or by treatment with benzylamine in a solvent polar, obtaining protected pyridine (V).

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d) these pyridines are subjected to deprotection conditions to leave the amino group released following common and known methods, such as acid treatment trifluoromethanesulfonic acid in any known organic solvent by a person skilled in the art, or bubbling hydrogen gas in presence of catalytic amounts of palladium on a support of activated carbon, to obtain pyridine of the type (SAW).

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e) condensation reaction type Friedländer of the basic heterocyclic system (VI) to achieve final products object of the present invention, of formula general (I). These derivatives were obtained following methodologies individuals according to the nature of the R_ {1} and R2.

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Another aspect of the present invention is refers to any of the compounds of general formula (I) for its use as a medicine or pharmaceutical composition, and preferably a medicament or pharmaceutical composition that is use for the treatment of diseases or diseases caused by oxidative processes, by processes of formation of clews neurofibrillar or, in general, of diseases susceptible to benefit from the biological activities shown by products described in the present invention, or of a salt, pharmaceutically acceptable derivative, prodrug or solvate of same.

The compounds of the present invention represented by formula (I) may include isomers, depending on the presence of multiple links (for example, Z and E), including optical isomers or enantiomers, depending on the presence of chiral centers in the chains R1 and R2. The individual isomers, enantiomers or diastereoisomers and the mixtures thereof fall within the scope of this invention. The individual enantiomers or diastereoisomers, as well as their mixtures, they can be separated by techniques conventional.

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The compounds of the present invention represented by formula (I) present in position 4 of the naphthyridine heterocycle, a hydrogen atom, lacking both of another type of substitution. This structural limitation could facilitate its binding to the enzyme catalytic site acetylcholinesterase, according to previously computed results analyzed.

As used herein, the term "derivative" includes both pharmaceutical compounds acceptable, that is, derivatives of the compound of formula (I) that they can be used in the preparation of a medicine, such as pharmaceutically acceptable derivatives since these may be useful in the preparation of pharmaceutically acceptable derivatives. The nature of the pharmaceutically acceptable derivative is not Critical, as long as it is pharmaceutically acceptable.

Also, within the scope of this invention the prodrugs of the compounds of formula (I) are found. He term "prodrug" as used herein includes a any compound derived from a compound of formula (I), by example, esters, including esters of carboxylic acids, esters of amino acids, phosphate esters, sulphonate esters of salts metallic, etc., carbamates, amides, etc., which, when administered an individual is able to provide, directly or indirectly, said compound of formula (I) in said individual. Advantageously, said derivative is a compound that increases the bioavailability of the compound of formula (I) when administered to an individual or that enhances the release of the compound of formula (I) in a receptor biological. The nature of said derivative is not always critical and when it can be administered to an individual and provide the compound of formula (I) in a biological receptor of an individual. The preparation of said prodrug can be carried out by Conventional methods known to those skilled in the art.

The compounds of the invention may be in crystalline form as free compounds or as solvates and it It is intended that both forms are within the scope of this invention. In this sense, the term "solvate", as here is used, includes both pharmaceutically acceptable solvates, is that is, solvates of the compound of formula (I) which can be used in the preparation of a medicine, such as solvates pharmaceutically unacceptable, which may be useful in the preparation of solvates or pharmaceutically acceptable salts. The Nature of the pharmaceutically acceptable solvate is not critical, as long as it is pharmaceutically acceptable. In one embodiment In particular, solvate is a hydrate. Solvates can be obtained by conventional methods of solvation well known to technicians in the field. For their application in therapy, the compounds of formula (I), their isomers, salts, prodrugs or solvates, will preferably be in a form pharmaceutically acceptable or substantially pure, that is, have a pharmaceutically acceptable level of purity excluding normal pharmaceutical additives such as diluents and carriers, and not including material considered toxic at levels of normal dosage. Purity levels for the beginning active are preferably greater than 50%, more preferably greater than 70%, more preferably greater than 90%. In a preferred embodiment, are greater than 95% of the compound of formula (I), or its salts, solvates or prodrugs.

Unless otherwise indicated, the compounds of the invention also include compounds that differ only in the presence of one or more isotopically enriched atoms. For example, compounds having said structure, except for the replacement of a hydrogen with a deuterium or tritium, or the replacement of a carbon with a carbon enriched in 13 C or 14 C or an enriched nitrogen at 15 N, they are within the scope of this
invention.

The compounds described herein invention, its pharmaceutically acceptable salts, prodrugs and / or solvates as well as the pharmaceutical compositions containing them can be used together with other additional drugs to Provide a combination therapy. Such additional drugs they can be part of the same pharmaceutical composition or, alternatively, they can be provided in the form of a separate composition for simultaneous administration or not to that of the pharmaceutical composition comprising a compound of formula (I), or a prodrug, solvate, derivative or a pharmaceutically salt acceptable of them.

Another preferred embodiment of the present invention relates to a pharmaceutical composition useful for the treatment of pathologies or diseases of the nervous system that can be caused by oxidative processes, by the development of neurofibrillary tangles or at least those processes play a pathologically significant role or, in general, of diseases likely to benefit from the biological activities shown for the products described in the present invention, hereafter pharmaceutical composition of the invention, comprising a compound, in therapeutically effective amount, of formula (I), or mixtures thereof, a salt, prodrug, solvate or stereoisomer pharmaceutically acceptable thereof along with a carrier, pharmaceutically acceptable adjuvant or vehicle, for administration to a patient

Another preferred embodiment of the present invention relates to the pharmaceutical composition of the invention in the group of neurodegenerative nervous system diseases to which they belong, by way of illustration and without limiting the scope of the invention: EA, Creutzfeldt-Jakob, Parkinson or Huntington, dementia with Lewy bodies or, in general, diseases resulting from a deterioration of neurons caused by oxidation processes, formation of neurofibrillar or other balls such as imbalances in calcium ion concentration, systems of neurotransmission, etc; that the nervous system of the affected patient is not able to
control.

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The scope of a neurodegenerative process in the The present invention is characterized by neuronal loss, failures in neurotransmission processes or processes derived from failures in the control of the oxidizing species created in the brain that give place to pathological oxidative stress or the development of clews neurofibrilar inside the neurons.

Another aspect of the present invention relates to to a pharmaceutical composition comprising at least one compound of general formula (I) or mixture of compounds and a vehicle pharmaceutically acceptable. Optionally said composition can It comprises another active substance.

"Pharmaceutical vehicles acceptable "that can be used in such compositions are the vehicles known to those skilled in the art and used usually in the elaboration of therapeutic compositions.

In another aspect, the present invention is refers to a method for the treatment of patients affected by diseases of the central nervous system in which they take place uncontrolled oxidative processes, deposit of clews neurofibrillar or other processes in which the products of the Present invention produce a beneficial effect. This treatment it consists of the administration to the individuals affected by these diseases of therapeutically effective amounts of a compound of formula (I), or a pharmaceutical composition that include By way of example, diseases contemplated in this invention are the EA, Creutzfeldt-Jakob, Parkinson or Huntington, dementia with Lewy bodies or, in general, diseases resulting from a deterioration of neurons caused by oxidative stress type processes, destabilization of microtubules by formation of neurofibrillar clews, ionic imbalances or failures in some neurotransmission system that the nervous system of the affected patient is not able to control.

In the sense used in this description, the expression "therapeutically effective amount" refers to the amount of agent or compound capable of carrying out the action therapeutic determined by its pharmacological properties, calculated to produce the desired effect and, in general, will come determined, among other causes, by the characteristics of the compounds, including the age, condition of the patient, the severity of the alteration or disorder, and of the route and frequency of administration.

In another particular embodiment, said therapeutic composition is prepared in the form of a solid form or aqueous suspension, in a pharmaceutically acceptable diluent. The therapeutic composition provided by this invention may be administered by any appropriate route of administration, for which said composition will be formulated in the pharmaceutical form appropriate to the route of administration chosen. In a particular embodiment, administration of the therapeutic composition provided by this invention is performed orally, topically, rectally or parenterally (including subcutaneously, intraperitoneally, intradermally, intramuscularly, intravenously, etc.). A review of the different pharmaceutical forms of drug administration and of the excipients necessary to obtain them can be found, for example, in the "Galician Pharmacy Treaty", C. Faulí i Trillo, 1993, Luzán 5, SA Ediciones , Madrid, or in other or similar ones of the Spanish and State Pharmacopoeias
United.

The use of the compounds herein invention is compatible with its use in protocols where compounds of the formula (I), or mixtures thereof are used by themselves or in combinations with other treatments or any procedure doctor.

Throughout the description and the claims the word "comprises" and its variants not they intend to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be partly detached of the description and in part of the practice of the invention. The The following examples are provided by way of illustration, and are not It is intended to be limiting of the present invention.

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Examples

The invention will be illustrated below through tests carried out by the inventors, who develop the process of selecting the compounds of the invention.

1. Obtaining the compounds of the invention

Compounds whose biological activity is object of the present invention were synthesized following a General procedure in organic synthesis. This procedure is represented in the following reaction scheme:

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Scheme one

Synthesis of the compounds of formula (I)

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This synthesis in several steps starts from acylacetate (II), commercial product or obtained by procedures common in organic synthesis, easily executed by Any expert in this field. This compound (II) was subjected to reaction with a dialkyl acetal derivative of dimethylformamide, to form a reaction intermediate with Michael acceptor structure, which, by reaction with cyanoacetamide under basic conditions with evolution of dimethylamine and subsequent cyclization 6-exo-trig, yield the corresponding 2-pyridone (III). In general, the resulting pyridone is obtained with sufficient purity so as not to require a subsequent purification, the generated compound is isolated from the medium of reaction by precipitation in slightly acidic medium. From This starting product, you need to replace the carbonyl in position 2 by an amine functional group. To carry out this transformation, the carbonyl needs to be transformed into a group easily outgoing, the formation of 2-chloropyridine (IV). This intermediate in the route of synthesis is formed in the presence of an excess of chlorinating electrophile, such as phosphorus pentachloride or phosphorus oxychloride, being able to act as a solvent in the reaction. The use of oxychloride phosphorus facilitates the product isolation process since, a once the reaction is finished (24h-2d), the derivatives of 2-Chloropyridine IV precipitate when adding ice. So, they are obtained by filtration and drying, without the need for greater purification. The chlorinated intermediate (IV) undergoes a substitution nucleophilic to incorporate in the position of the Cl atom an amine, reaction that can be done in several ways, for example by ammonia bubbling, or by treatment with benzylamine in a polar solvent, obtaining protected pyridine (V). The use of Benzylamine requires a subsequent step. However, it is the method of choice because it avoids the use of high-bottled gas ammonia pressure, not without danger to the researcher. Thus they obtain the type (VI) precursors through the elimination of benzyl group in (V), under classical conditions of deprotection of this type of functionality, such as hydrogen gas bubbling in the presence of catalytic amounts of Pd on a support of active carbon Alternatively and to avoid the use of gases dangerous, which sometimes need an increase in pressure in the reactor, can be subjected (V) to an acid treatment trifluoromethanesulfonic in organic solvent, which yields analogously pyridine type (VI). Alternatively it is possible to reach pyridine VI from the alkyl ester of β-aminocrotonic acid and the 2-ethoxymethylenemalononitrile in the presence of acid acetic, in a single reaction step, but with low yield. These pyridines are the necessary substrate for the reaction of Friedlander type condensation with cyclic ketones in the presence of a Lewis acid, to get the final products object of the present invention, of general formula (I). The products are obtained with good performance, and if you consider all the steps of reaction, the overall performance of the synthetic route from products Commercial is around 18-26%. This performance can be increased in the last step of condensation of Friedlánder with the use of a microwave appliance. It has been tested this method with the synthesis of compound 2, increasing the yield in the last step of 55 to 90%. This efficiency synthetic allows these compounds to be considered accessible for pilot plant preparation by the pharmaceutical industry.

In particular, and following the protocol of Synthesis represented in Scheme 1, were obtained and characterized The following compounds:

Compound 1

Methyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo [ b ] [1,8] naphthyridine-3-carboxylate . Solid yellow. Melting point> 200 ° C; IR (KBr) ν 3338, 3229, 2941, 2862, 1716, 1620, 1601, 1568, 1543, 1437, 1361, 1284, 1246, 1116,1070, 802, 779 cm -1; 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.82 (s, 1H, H4), 5.19 (bs, 2H, NH 2), 3.94 (s, 3H, CH 3 O), 3.07 (m, 2H, H9), 2.95 [s, 3H, CH 3 C (2)], 2.59 (m, 2H, H6), 1.93 (m, 4H, H7, H8); 13 C NMR (CDCl 3, 75.4 MHz) δ (ppm): 166.4 (C = O), 161.9 (C9a), 159.6 (C2), 154.1 (C10a), 150.9 (C5), 136.0 ( C4), 119.7 (C3), 109.9 (C5a), 108.3 (C4a), 52.1 ( C H 3 O), 33.4 (C9), 25.2 [ C H 3 C (2)], 23.3 (C6) , 22.1, 22.0 (C7, C8); MS (APIES +): m / z 272 [(M + 1) +, 100], 248 (12), 205 (13). Purity: Anal. Elem. Calcd. For C 15 H 17 N 3 O 2: C, 66.40; H, 6.32; N, 15.49. Found: C, 66.10; H, 6.61; N, 15.18.

Compound 2

Ethyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo [ b ] [1,8] naphthyridine-3-carboxylate . Solid yellow. Melting point> 200 ° C; IR (KBr) ν 3374, 3324, 3182, 2934, 1717, 1664, 1602, 1577, 1546, 1434, 1363, 1350, 1252, 1222, 1120, 1072, cm -1; 1 H NMR (CDCl 3, 300 MHz) δ (ppm) 8.82 (s, 1H, H4), 5.33 (bs, 2H, NH 2), 4.39 (q, J = 7.5 Hz, 2H, CO 2 C H 2 CH 3), 3.05 (m, 2H, H9), 2.91 [s, 3H, CH 3 C (2)], 2.58 (m, 2H, H6 ), 1.92 (m, 4H, H7, H8), 1.41 (t, J = 7.5 Hz, 3H, CO 2 CH 2 C H 3); 13 C NMR (CDCl 3, 75.4 MHz) δ (ppm) 166.7 (C = O), 163.9 (C9a), 162.0 (C2), 154.6 (C10a), 149.5 (C5), 135.0 (C4 ), 121.8 (C3), 111.5 (C5a), 109.0 (C4a), 61.8 (O C H 2 CH 3), 34.2 (C9), 26.4 [ C H 3 C (2)], 23.9 (C6), 22.8 (C7, C8), 14.7 ( C H 3 CH 2 O); MS (APIES +): m / z 286 [(M + 1) +, 100], 593 [(2 x M + Na) +, 5], 308 [(M + Na) + }, 4], 272 (10), 258 (12). Purity: Anal. Elem. Calc. For C 16 H 19 N 3 O 2: C, 67.35; H, 6.71; N, 14.73. Found: C, 67.12; H, 6.54; N, 14.55.

Compound 3

Methyl 5-amino-2-methyl-7,8-dihydro-6 H -cyclopenta [ b ] [1,8] naphthyridine-3-carboxylate . Solid yellow. Melting point> 200 ° C; IR (KBr) ν 3317, 3188, 2951, 2844, 1724, 1645, 1601, 1549, 1431, 1358, 1259, 1114, 802, 777 cm -1; 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.74 (s, 1H, H4), 4.76 (bs, 2H, NH 2), 3.97 (s, 3H, CH 3 O), 3.16 (t, J 7.8 = 7.6 Hz, 2H, H8), 2.98 [s, 3H, CH 3 C (2)], 2.86 (t, J 6.7 = 7.6 Hz, 2H, H6), 2.23 (quit, 2H, J 6.7.8 = 7.6 Hz, H7); 13 C NMR (CDCl 3, 75.4 MHz) δ (ppm) 171.8 (C = O), 166.5 (C8a), 158.9 (C2), 157.0 (C9a), 148.1 (C4), 135.8 (C5 ), 119.5 (C3), 114.1 (C5a), 109.0 (C4a), 52.1 ( C H 3 O), 35.1 (C8), 27.5 [ C H 3 C (2)], 25.3 (C6), 21.8 (C7); MS (APIES +): m / z 258 [(M + 1) +, 100], 245 (11), 205 (10), 157 (10). Purity: Anal. Elem. Calcd. For C 14 H 15 N 3 O 2: C, 65.35; H, 5.88; N, 16.33. Found: C, 65.21; H, 5.78; N, 16.09.

Compound 4

Ethyl 5-amino-2-methyl-7,8-dihydro-6 H -cyclopenta [ b ] [1,8] naphthyridine-3-carboxylate . Solid yellow. Melting point> 200 ° C; IR (KBr) ν 3329, 3176, 2964, 1716, 1657, 1604, 1550, 1433, 1400, 1358, 1252, 1217, 1117, 1086, 1051, 806, 779 cm -1; 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.74 (s, 1H, H4), 4.80 (bs, 2H, NH 2), 4.44 (q, J = 7.2 Hz, 2H, CO 2 C H 2 CH 3), 3.16 (t, J 7.8 = 7.6 Hz, 2H, H8), 2.98 [s, 3H, CH 3 C ( 2)], 2.88 (t, J 6.7 = 7.6 Hz, 2H, H6), 2.23 (quit, 2H, J 6.7.7 = 7.6 Hz, H7), 1.45 (t, J = 7.2 Hz, 3H, CO 2 CH 2 C H 3); 13 C NMR (CDCl 3, 50.2 MHz) δ (ppm) 171.6 (C = O), 166.1 (C8a), 158.7 (C2), 156.9 (C9a), 148.0 (C4), 135.6 (C5 ), 120.0 (C3), 114.0 (C5a), 109.0 (C4a), 60.8 (O C H 2 CH 3), 35.0 (C8), 27.5 (C6), 25.2 [ C H 3 C ( 2)], 21.8 (C7), 14.1 (OCH2 C H3); MS (APIES +): m / z 272 [(M + 1) +, 100], 258 (8), 245 (7). Purity: Anal. Elem. Calcd. For C 15 H 17 N 3 O 2: C, 66.40; H, 6.32; N, 15.49. Found: C, 66.41; H, 6.61; N, 15.22.

Compound 5

Methyl 5-amino-2-methyl-7,8,9,10-tetrahydro-6 H -cyclohepta [ b ] [1,8] naphthyridine-3-carboxylate . Solid yellow. Melting point> 200 ° C; IR (KBr) ν 3330, 3199, 2918, 2850, 1720, 1651, 1601, 1579, 1543, 1429, 1361, 1346, 1257, 1105, 1082, 810, 779 cm -1; 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.77 (s, 1H, H4), 5.03 (bs, 2H, NH 2), 3.96 (s, 3H, CH 3 O), 3.19 (m, 2H, H10), 2.96 [s, 3H, CH 3 C (2)], 2.75 (m, 2H, H6), 1.98-1.46 (m, 6H, H7, H8, H9); 13 C NMR (DMSOd 6, 75.4 MHz) δ (ppm) 169.1 (C = O), 166.4 (C10a), 159.0 (C2), 154.5 (C11a), 149.2 (C5), 136.0 (C4 ), 120.1 (C3), 114.9 (C5a), 109.2 (C4a), 52.0 (OCH_ {3}), 39.2 (C10), 31.4 (C9), 27.3 (C8), 26.2 (C6), 25.0, 24.9 (C2 , C7); MS (APIES +) m / z 286 [(M + 1) +, 100], 248 (12), 205 (15). Purity: Anal. Elem. Calcd. For C 16 H 19 N 3 O 2 {c} ¼ H 2 O: C, 66.30; H, 6.78; N, 14.50. Found: C, 66.60; H, 6.80; N, 14.12.

Compound 6

Ethyl 5-amino-2-methyl-7,8,9,10-tetrahydro-6 H -cyclohepta [ b ] [1,8] naphthyridine-3-carboxylate . Solid yellow.
Melting point> 200 ° C; IR (KBr) ν 3381, 3327, 3153, 2923, 2850, 1714, 1670, 1603, 1576, 1543, 1344, 1288, 1254, 1223, 1111, 1082, 1049, 812, 781 cm -1; 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.75 (s, 1H, H4), 5.03 (bs, 2H, NH 2), 4.44 (q, J = 7.0 Hz, 2H, CO 2 C H 2 CH 3), 3.19 (m, 2H, H10), 2.96 [s, 3H, CH 3 C (2)], 2.75 (m, 2H, H6 ), 2.00-1.60 (m, 6H, H7, H8, H9), 1.44 (t, J = 7.0 Hz, 3H, CO 2 CH 2 C H 3); 13 C NMR (DMSOd 6, 75.4 MHz) δ (ppm) 169.1 (C = O), 166.1 (C10a), 158.8 (C2), 154.6 (C11a), 149.1 (C5), 135.9 (C4 ), 120.5 (C3), 114.9 (C5a), 109.3 (C4a), 60.8 (O C H 2 CH 3), 39.2 (C10), 31.5 (C9), 27.3 (C8), 26.2 (C6) , 25.1, 25.0 (C2, C7), 14.1 (OCH2 C H3); MS (APIES +) m / z 300 [(M + 1) +, 100], 205 (17), 157 (13). Purity: Anal. Elem. Calcd. For C 17 H 21 N 3 O 2: C, 68.20; H, 7.07; N, 14.04. Found: C, 68.12; H, 6.89; N, 13.92.

Compound 7

Methyl 5-amino-2-methyl-6,7,8,9,10,11-hexahydrocycloocta [ b ] [1,8] naphthyridine-3-carboxylate . Solid white. Melting point> 200 ° C; IR (KBr) ν 3349, 2923, 2851, 1725, 1713, 1620, 1600, 1571, 1541, 1432, 1361, 1351, 1291, 1260, 1249, 1109, 1093 cm -1. 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.80 (s, 1H, H4), 5.10 (bs, 2H, NH 2), 3.97 (s, 3H, CH 3 O), 3.15 (m, 2H, H11), 2.98 [s, 3H, CH 3 C (2)], 2.88 (m, 2H, H6), 1.90 (m, 2H, H10), 1.73 (m , 2H, H7), 1.43 (m, 4H, H8, H9); 13 C NMR (CDCl 3, 75.4 MHz) δ (ppm) 167.6 (C = O), 166.5 (C11a), 161.9 (C2), 148.2 (C12a), 146.2 (C5), 134.9 (C4 ), 121.4 (C3), 114.2 (C5a), 109.0 (C4a), 52.4 (OCH3), 36.2 (C11), 30.8 (C10), 27.8 (C7), 26.3, 26.2 (C8, C9), 25.9 (C2) , 24.7 (C6). MS (APIES +) m / z 300 [(M + 1) +, 100], 322 [(M + Na) +, 13], Purity: Anal. Elem. Calcd. For C 17 H 21 N 3 O 2: C, 68.20; H, 7.07; N, 14.04. Found: C, 68.50; H, 7.31; N, 14.08.

Compound 8

Ethyl 5-amino-2-methyl-6,7,8,9,10,11-hexahydrocycloocta [ b ] [1,8] naphthyridine-3-carboxylate . Solid white. Melting point> 200 ° C; IR (KBr) ν 3345, 2920, 2846, 1716, 1618, 1599, 1570, 1541, 1431, 1356, 1350, 1290, 1259, 1242, 1167, 1107, 1090, 818, 779 cm -1; 1 H NMR (CDCl 3, 200 MHz) δ (ppm) 8.75 (s, 1H, H4), 5.02 (bs, 2H, NH 2), 4.43 (q, J = 7.0 Hz, 2H, CO 2 C H 2 CH 3), 3.14 (m, 2H, H11), 2.97 [s, 3H, CH 3 C (2)], 2.87 (m, 2H, H6 ), 1.88 (m, 2H, H10), 1.72 (m, 2H, H7), 1.43 (t, J = 7.0 Hz, 3H, CO 2 CH 2 C H 3), 1.38 (m , 4H, H8, H9); 13 C NMR (CDCl 3, 75.4 MHz) δ 166.6 (C11a), 166.1 (C = O), 159.3 (C2), 154.6 (C12a), 149.9 (C5), 136.0 (C4), 120.5 (C3), 112.5 (C5a), 108.8 (C4a), 60.8 (O C H 2 CH 3), 35.7 (C11), 30.7 (C10), 27.8 (C7), 26.0, 25.8 (C8, C9 ), 25.1 [ C H 3 C (2)], 23.7 (C6), 14.1 (OCH 2 C H 3); MS (APIES +) m / z 314 [(M + 1) +, 100], 205 (12). Purity: Anal. Elem. Calcd. For C 18 H 23 N 3 O 2: C, 68.98; H, 7.40; N, 13.41. Found: C, 68.69; H, 7.68; N, 13.12.

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2. Biological activities studied in the compounds of the invention 2.1 Neuroprotective properties of the compounds of the invention

The cytoprotective effect of the compounds in human neuroblastoma cells was evaluated, specifically the neuroprotective potential of these compounds against (i) the oxidative stress produced by rotenone and oligomycin A, blockers of the mitochondria respiratory chain as described in J. Neurochem 1992 , 59 , 1609-1623 and in Toxicological Sciences 2004 , 79 , 137-146, respectively, and (ii) the hyperphosphorylation of the tau protein induced by okadaic acid which is an accepted model for neuronal death that occurs in AD and which is related to tau hyperphosphorylation ( Neuroscience 2004 , 126 , 277-284; Neurosci Lett . 1997 , 235 , 149-153).

The viability parameter that was measured in the first case was the activity of the enzyme lactate dehydrogenase (LDH hereinafter), an enzyme that is released to the extracellular medium when the cell dies ( J. Pharmacol. Exp. Ther . 2005 , 315 , 1346-1353). In experiments with okadaic acid, the assay based on the metabolic reduction of 3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazole (MTT) bromide conducted by the cell was used to measure cell survival mitochondrial enzyme succinate dehydrogenase in a blue compound (formazan), which allows to determine the mitochondrial functionality of the treated cells ( J. Immunol. Meth . 1983 , 65 , 55-63). Okadaic acid produces mitochondrial changes in cells treated with this toxic, causing a decrease in mitochondrial membrane potential ( Toxicology in Vitro 2001 , 15 , 199-208), thus initiating the process that will lead to cell death. Therefore, a method such as MTT that allows us to know the metabolic state of mitochondria in cells subjected to incubation with okadaic acid was considered more appropriate.

The experimental method used, following a previously described procedure ( Neuropharmacology 2004 , 46 , 103-114) is as follows: SHSY5Y human neuroblastoma cells were seeded and cultured in a DMEM (Dulbecco's modified Eagle's medium) medium containing 15 non-essential amino acids and supplemented with 10% fetal calf serum, 1 millimolar glutamine, 50 units per milliliter of penicillin and 50 micrograms per milliliter of streptomycin, keeping them at 37 ° C in humidified air containing 5% carbon dioxide. In the assays, SH-SY5Y cells were subcultured in 48-well plates with a seeding density of 1x105 cells per well. In the cytotoxicity experiments, the cells thus prepared were treated with the compounds to be measured in serum-free DMEM.

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To study the cytoprotective action of different compounds against cell death induced by a combination of rotenone with oligomycin A 30 micromolar and 10 micromolar respectively or with 30 nanomolar okadaic acid, all the compounds (1 to 8) were evaluated at the concentration of 1 micromolar For this, the cells were treated with the product to Evaluate for 24 hours. Afterwards, the media were replaced by fresh media that still contained the compound plus the agents cytotoxic, and were thus maintained for an additional period of 24 hours. The cell viability was checked in the case of incubation with the combination rotenone / oligomycin A measuring the LDH enzyme activity using the "Cytotoxicity Cell" kit Death "(Roche-Boehringer Mannheim) following the manufacturer's instructions for said kit. The samples are analyzed spectrophotometrically in a plate reader (Labsystems iEMS Reader MF), using the appropriate filter (490 nm), obtaining absorbance values through the program DeltaSOFTII Version 3.71 EMS. Total LDH activity was defined. as the sum of intra and extracellular LDH activities. The LDH activity released by cells upon death was defined as the percentage of extracellular LDH activity versus activity Total LDH

When the cytotoxic used was acid Okadaic feasibility assessment was done by measuring the reduction of a soluble tetrazolium (MTT) salt, yellow in color, to a blue insoluble formazan. To do this, 50 was added microliters of commercial MTT reagent (Sigma) to each well with 500 microliters of medium holding the culture plates for 3 hours in darkness and at 37 ° C. After this time he retired gently supernatant medium, leaving a precipitate deposited which was dissolved with 300 microliters of dimethylsulfoxide (DMSO). After 10 minutes while stirring, samples were taken from the wells and the absorbance in a plate reader (Labsystems iEMS Reader MF) at a wavelength of 540 nanometers. Absorbance values obtained with the toxic alone and with each compound in the presence of Toxic were subtracted from the absorbance value obtained under conditions Basal, without treatment. The value obtained from the subtraction of Basal absorbance values less toxic alone, 100% was considered of death and the values obtained with the compounds in the presence of Toxic were normalized as percentages of that value. For calculate the survival percentage, these values were subtracted of 100

In all pharmacological trials, a positive control was used as a comparison and to assess the goodness of the method used. In the case of rotenone / oligomycin A experiments, N-acetylcysteine (NAC), a well-known antioxidant, was used; when okadaic acid was used as toxic, galantamine was used as a positive control, which in previous studies had demonstrated a protective effect ( J. Pharmacol. Exp. Ther . 2005 , 315 , 1346-1353).

The results obtained for the compounds described as compounds 1 to 8 shown in Tables 1 and 2, They are expressed as a percentage of neuroprotective activity.

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TABLE 1 Percentage of neuroprotection against the mixture of rotenone (30 µM) and oligomycin A (10 µM) of the 1,8-naphthyridine derivatives at the concentration of 1 micromolar

10

The results are the average of 4 experiments independent (in triplicate). * p <0.05.

These results indicate that the compounds object of the present invention are able to reduce so moderate the presence of radicálicas species with the consequent neuroprotective effect, which makes them potential drugs for the treatment of pathologies generated or favored by stress oxidative or presence of radicálicas species in general.

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TABLE 2 Percentage of neuroprotection against okadaic acid 30 nM of 1,8-naphthyridine derivatives a 1 micromolar concentration

eleven

The results are the average of 8 experiments independent (in triplicate). * p <0.05, ** p <0.01, *** p < 0.001.

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These results show that most of the compounds object of the present invention protect notable against death induced by the formation of clews neurofibrillary, with values close to 60% protection for some of them.

2.2 Properties of the compounds object of the invention as inhibitors of the enzymes acetyl and butyrylcholinesterase

The inhibitory activity of the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) of the compounds studied by the method of Ellman ( Biochem. Pharmacol . 1961 , 7 , 88-95) was evaluated. The electric eel acetylcholinesterase enzyme ( Electrophorus electricus ), a great analogy to the human neuronal, was chosen as the neuronal model. To comparatively analyze the hypothetical peripheral inhibition, potentially associated with the adverse effects found in the administration of anticholinesterase agents, the AChE inhibitory activity extracted from human erythrocytes was evaluated. To evaluate the inhibition of BuChE, the one extracted from equine serum was chosen.

Inhibition of cholinesterase enzymes is the predominant therapeutic target in the clinic for the treatment of AD. This therapeutic approach is based on the so-called cholinergic hypothesis ( Science 2006 , 314 , 777-781), which suggests that the selective loss of cholinergic neurons in AD causes a deficit of the neurotransmitter acetylcholine (ACh) in specific regions of the brain that control learning and memory ( Lancet Neurol . 2003 , 2 , 539-547). Thus, there are three drugs approved by the international drug regulatory administrations (donepecyl, galantamine and rivastigmine) that improve the symptoms of AD through the inhibition of AChE, the enzyme responsible for hydrolyzing ACh, consequently raising the levels of this neurotransmitter in the synaptic cleft ( Pharmacol. Res . 2004 , 50 , 441-451). Recently, a renewed interest in AChE inhibitors has been generated, stimulated by the potential role of AChE in accelerating the formation of amyloid fibrils in the brain and the generation of stable complexes with Aβ ( Neuron 1996 , 16 , 881-891 ). This feature involves the anionic peripheral binding site (PAS) of AChE, as evidenced by the fact that propidium iodide, which binds to PAS, affects Aβ aggregation in vitro , while inhibitors that are bind to the catalytic site do not present this effect.

The experimental method used, following the procedure previously described ( Biochem. Pharmacol . 1961 , 7 , 88-95) is as follows: for the measurement of AChE inhibition (either extracted from electric eel or human serum) carry out the reaction in wells with a final volume of 3 ml of a PBS buffer solution at pH 8, containing 0.035 units / ml of AChE and 0.35 mM of 5,5'-dithiobis-2-nitrobenzoic acid (DTNB), Used to produce the yellow anion of 5-thio-2-nitrobenzoic acid. Inhibition curves with the different compounds were performed in quadruplicate by incubating with at least 9 concentrations of the compounds for 10 min. After this time, the 0.35 mM acetylthiocholine iodide substrate was added from a 10 mM stock solution. To measure the inhibition of BuChE extracted from equine serum, the reaction was carried out in wells with a final volume of 3 ml of a PBS buffer solution at pH 8, containing 0.05 units / ml of BuChE and 0.35 mM of 5,5'-dithiobis-2-nitrobenzoic acid (DTNB). Inhibition curves with the different compounds were performed in quadruplicate by incubating with at least 9 concentrations of the compounds for 10 min. After this time, the 0.5 mM butyrylthiocholine iodide substrate was added from a 10 mM stock solution. In both types of experiments (AChE and BuChE), a quadruplicate sample without compound was always present to yield 100% of the enzymatic activity. At 15 min, the color production at 412 nm was measured in a 96-well plate spectrophotometric reader as a signal of enzymatic activity.

The concentration of drug that produces the 50% inhibition of enzyme activity (IC 50) was calculated by sigmoidal regression of the logarithmic representation of the concentration. The results were expressed as mean ± error Standard of at least three experiments. The results obtained for the compounds described as compounds 1 to 8 are shown in Table 3

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TABLE 3 Cholinesterase enzyme inhibitory activity by part of the compounds derived from 1,8-naphthyridine

13

The results are the average of at least 3 independent experiments (in quadruplicate). Where S (BuChE /
eeAChE) refers to the BuChE / eeAChE selectivity.

These results indicate that the compounds object of the present invention are able to inhibit enzymes cholinesterase in a moderate and dual way, except 1 and 2, which show a potent inhibitory and selective activity for AChE. Is remarkable its greater activity on electric eel AChE, isoform very similar to the human neuronal, which on the AChE of human red blood cells This discovery is important in that could mean a lower incidence of side effects associated with the inhibition of this peripheral enzyme. These results make them potential drugs for the Alzheimer's disease treatment.

Claims (14)

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1. Compound of general formula (I): 14 where

R_ {1} and R2 are the same or different and are selected in a way independent of an alkyl group (C 1 -C 10); Y

n

is an integer with a value between 0 to 5.

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2. Compound according to claim 1, wherein R 1 and / or R 2 are an alkyl group (C_ {1} -C_ {6}). 3. Compound according to claim 2, wherein R1 is methyl or ethyl. 4. Compound according to any of the claims 2 or 3, wherein R2 is methyl. 5. Compound according to any of the claims 1 to 4, where n is 0, 1, 2 or 3. 6. Compound according to any of the claims 1 to 5, selected from the list comprising:

?

Methyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo [ b ] [1,8] naphthyridine-3-carboxylate,

?

Ethyl 5-amino-2-methyl-6,7,8,9-tetrahydrobenzo [ b ] [1,8] naphthyridine-3-carboxylate,

?

Methyl 5-amino-2-methyl-7,8-dihydro-6 H -cyclopenta [ b ] [1,8] naphthyridine-3-carboxylate,

?

Ethyl 5-amino-2-methyl-7,8-dihydro-6 H -cyclopenta [ b ] [1,8] naphthyridine-3-carboxylate,

?

Methyl 5-amino-2-methyl-7,8,9,10-tetrahydro-6 H -cyclohepta [ b ] [1,8] naphthyridine-3-carboxylate,

?

Ethyl 5-amino-2-methyl-7,8,9,10-tetrahydro-6 H -cyclohepta [ b ] [1,8] naphthyridine-3-carboxylate,

?

Methyl 5-amino-2-methyl-6,7,8,9,10,11-hexahydrocycloocta [ b ] [1,8] naphthyridine-3-carboxylate, and

?

Ethyl 5-amino-2-methyl-6,7,8,9,10,11-hexahydrocycloocta [ b ] [1,8] naphthyridine-3-carboxylate.

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7. Procedure for obtaining the compounds of formula (I) according to any one of claims 1 to 6, which It comprises the following steps:

to.

reacting an alkyl acylacetate of the formula (II),

fifteen

quad

where: R 1 and R 2 have been described in the claim 1,

quad

with a dimethylformamide diaalkylacetal and subsequently with cyanoacetamide under basic conditions;

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b.

nucleophilic substitution on the 2-pyridone of formula (III) obtained in step (a) by an excess of phosphorus oxychloride:

16

C.

nucleophilic substitution on pyridine of formula (IV), obtained in step (b), incorporating at the position of the atom of Cl an amine:

17

d.

deprotection of the pyridines of formula (V), obtained in step (c), leaving the amino group free, and

18

and.

Friedlander type system condensation basic heterocyclic of formula (VI), obtained in step (d):

19 8. Method according to claim 7, in which step (c) is carried out by ammonia bubbling or by treatment with benzylamine in a polar solvent. 9. Procedure according to any of the claims 7 or 8, wherein step (d) is carried out by treatment with solvent trifluoromethanesulfonic acid organic or by bubbling hydrogen gas in the presence of quantities Palladium catalysts on an active carbon support. 10. Use of the compound according to any of the claims 1 to 6, for the preparation of a medicament. 11. Use of the compound according to any of the claims 1 to 6, for the preparation of a medicament for the treatment of neurodegenerative diseases. 12. Use of the compound according to claim anterior, where neurodegenerative diseases are selected from the list that includes Alzheimer's disease, Parkinson's and Huntington's disease. 13. Pharmaceutical composition comprising less a compound of general formula (I) together with one or more pharmaceutically acceptable excipients. 14. Pharmaceutical composition according to previous claim, further comprising one or more agents Therapeutic active.