EA045675B1 - METHODS FOR OBTAINING DICARBOXYLIC ACID BISAMIDE - Google Patents

Description

The invention relates to new methods for producing compounds of formula 2

or pharmaceutically acceptable salts thereof having the ability to complex or chelate metal ions.

State of the art

Metal ions play an important role both in the normal functioning of cells and the whole organism, and in the development of pathologies.

There are known drugs that exert their effect due to the ability to chelate metal ions. In this regard, a search is currently underway for non-toxic compounds that can highly efficiently and selectively chelate metal ions and are suitable for biomedical use.

Compounds with chelating properties were found among various classes of mono- and ditol compounds, disulfides, azo compounds, nitrosoaromatic compounds, polyaminocarboxylic acid derivatives, thiosemicarbazone, pyridoxal isonicotinoylhydrazone, quinoline, adamantane, pyrogallol, phenanthroline, thiopyrophosphates and others. In addition, they are noted among other natural compounds, such as, for example, carnosine, phytin, pectin. Of greatest interest are compounds that have several functional groups that can act as electron donors during complex formation. In this regard, such compounds may be ligands that specifically interact with ions of a metal or group of metals.

Currently widely known complexing agents are derivatives of polyaminocarboxylic acids (for example, EDTA), D-penicillamine, and polycyclic cryptands, which are successfully used for heavy metal poisoning. Deferroxamine is used as an iron chelator in some iron overload conditions and hematochromatosis. In addition, it is possible to use chelators for pathologies associated with excess Ca, for example, arthrosis, atherosclerosis, and kidney stones. Chelation therapy is also known to prevent the deposition of cholesterol and restore its level in the blood, lower blood pressure, avoid angioplasty, suppress unwanted side effects of certain heart medications, remove calcium from cholesterol plaques, dissolve blood clots and restore the elasticity of blood vessels, normalize arrhythmia, and prevent aging. , restores the strength of the heart muscle and improves heart function, increases intracellular potassium content, regulates mineral metabolism, is useful in the treatment of Alzheimer's disease, prevents cancer, improves memory and exhibits many other positive effects. However, strong chelators currently used in chelation therapy usually have toxic effects, which manifest themselves mainly in damage to the mucous membrane of the small intestine and impaired renal function. In some cases, rapid administration of large quantities of known chelators may impair muscle excitability and blood clotting. In addition, strong chelators can interact with beneficial bioelements (Na, K, Mg, Ca), and can also change the activity of vital metalloenzymes [Zelenin K.N. Complexons in medicine, Soros Educational Journal, 2001, vol. 7, no. 1, pp. 45-50].

In this regard, an active search is being carried out for new highly effective chelators with a chelating ability sufficient to produce a biological effect in vivo, without side effects.

The idea of using chelation therapy in the case of viral diseases such as HIV, human papilloma, herpes, hepatitis C and others is especially relevant.

A promising target for this seems to be the zinc-binding sites in the structure of viral proteins - the so-called zinc fingers.

Several compounds have now been identified that affect the zinc fingers of important proteins of these viruses.

The article by Andreas J.K., Boorganic & Medicinal chemistry, 2003, v.11, p.4599-4613, describes an adamantane derivative with the trivial name bananain, which is a chelator of zinc ions. It is thought to be chemically suited to remove zinc from the HIV NCp7 protein. An aza derivative with the above-mentioned mechanism of action, azadicarbonamide, is in stage I/II clinical trials against progressive AIDS.

In the article, Rice W.G., Schaeffer S.A., Harten B., Nature, 1993, v.4, p.473-475, disclosed 3-nitrosobenzamide, which removes zinc from the NCp7 protein of HIV, inhibiting HIV replication and its pathogenicity in vitro and in vivo.

The zinc finger region of the protein was also chosen as a drug target.

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E6 human papillomavirus. This virus is a possible mediator in the etiology of cervical carcinoma.

The article Beerheide W., Bernard H.-U., Tan Y.-J., Ganesan A.J., National Cancer Institute, 1999, v.91, No. 14, 1211-1220, describes in vitro tests of aza compounds, disulfide and nitrosoaromatic derivatives . Compounds such as 4,4'-dithiodimorpholine have been shown to provoke the release of zinc ions. As a result, changes in the structure of the viral protein and disruption of its functions associated with the biology and pathology of the human papillomavirus were observed. However, clinical trials of these compounds in this regard have not yet been completed, and their effectiveness can only be judged on the basis of in vitro studies.

The above compounds are considered promising for the development of drugs against cervical cancer, genital warts and latent human papillomavirus infections of the genital organs. Hepatitis C virus is one of the most widespread human pathogens. Modern therapy for hepatitis C is based almost exclusively on the use of interferon, as well as its combination with a nucleoside analogue - ribavirin [Kozlov M.V., Polyakov K.M., Ivanov A.V., Biochemistry, 2006, v. 71, No. 9, pp. 1253-12594]. It should be noted that this therapy is not very effective.

Regarding the development of therapeutic agents against the hepatitis C virus, one of the targets is the NS3-serine proteinase, in maintaining the stability of the structure of which the zinc region plays an important role [Andrea Urbani, Renzo Bazzo, Maria Chiara Nardi, Daniel Oscar Cicero, Raffaele De Francesco, J Biol. Chem, 1998, v.273, no. 30, p. 18760-18769]. Inhibition or modification of its activity by the use of zinc-extracting compounds has been assessed in some literature as a promising strategy for the management of hepatitis C virus disease.

In the article Timothy L. Tellinghuisen, Matthew S. Paulson, Charles M. Rice, J. Virology, 2006, v. 80, no. 15, p. 7450-7458, described that metal chelators (EDTA and 1,10-phenanthroline) were effective protease inhibitors assessed against NS2/3 autocleavage. There is also evidence that 1,10-phenanthroline acted in this case precisely through chelation of zinc.

In the article Sperandio D., Gangloff AR, Litvak J. Goldsmith R., Bioorg. Med. Chem. Lett., 2002, v.12, No. 21, 3129-3133, describes the screening of a group of bisbenzimidazoles in order to search for inhibitors of the serine protease NS3/NS4A of the hepatitis C virus, which also led to the identification of a corresponding powerful Zn ²⁺ -dependent inhibitor.

When developing new approaches to the treatment of hepatitis C, another attractive target is the RNA-dependent RNA polymerase of the hepatitis C virus (viral protein NS5B), which has a zinc-binding site in its structure [Timothy L. Tellinghuisen, Matthew S. Paulson, Charles M. Rice, J. Virology, 2006, v. 80, no. 15, p. 7450-7458].

Currently known inhibitors of the RNA-dependent RNA polymerase of the hepatitis C virus can be divided into two main classes: nucleoside derivatives and non-nucleoside inhibitors of various natures [Maria Bretner, Acta biochemica polonica, 2005, v.52, No. 1, p. 57-70]. In addition, inhibition of the activity of this enzyme by pyrogallol derivatives was found. It is noteworthy that the mechanism of inhibition by pyrogallol derivatives is believed to be the chelation of magnesium cations taking part in the catalytic act at the stage of transfer of the phosphoryl residue [Kozlov M.V., Polyakov K.M., Ivanov A.V., Biochemistry, 2006, 71, No. 9, pp. 1253-12594].

Diseases caused by herpes viruses are widespread. Thus, several human herpes viruses are known - herpes simplex virus 1 and 2 (HSV-1 and HSV-2), cytomegalovirus (CMV), varicella zoster virus, Epstein-Barr virus. The destructive effects that this has on the central nervous system cause diseases such as encephalitis and meningitis. There may be interest in studying the effect of zinc chelating compounds, for example, diethylenetriamine pentaacetic acid, on the inhibition of human cytomegalovirus replication in vitro [Kanekiyo M., Itoh N., Mano M., Antiviral Res., 2000, v. 47, p. 207-214].

However, it should be noted that herpesviruses, like the above viruses, have proteins containing a zinc finger motif. Chemical changes in the zinc finger can lead to the release of zinc and changes in the structure of the functioning of viral proteins [Yan Chen, Christine M. Livingston, Stacy D. Carrington-Lawrence, J. of Virology, 2007, v.81, No. 16, p. 8742-8751].

Zinc fingers can serve as a target for new generation antiviral drugs. Several such compounds have already been identified. However, at present their effectiveness can only be judged based on in vitro studies.

The above information allows us to assert the important role of metal ions both in the normal functioning of cells and the whole organism, and in the development of pathologies. The ability of some compounds to chelate metal ions can serve as the basis for the creation of drugs capable of treating a variety of diseases, in particular viral ones.

In the article Megan Whitnall, Jonathan Howard, Prem Ponka, A class of iron chelators with a wide spectrum of potent antitumor activity that overcomes resistance to chemotherapeutics, PNAS, 2006, v. 103, no. 40, p. 14901-14906, effective iron chelators have been disclosed, which demonstrate high antiproliferative and antitumor activity, comparable to the activity of known cytostatics, and are promising for clinical studies.

In the article Kik K., Szmigiero L., Dexrazoxane (ICRF-187) - a cardioprotectant and modulator of some anticancer drugs, Postepy Hig Med Dosw Online, 2006, v. 60, p. 584-590, it is indicated that some iron chelators can be used as assistants in anticancer therapy, as they have a cardioprotective effect.

Chelation of copper ions inhibits angiogenesis and reduces tumor growth [Yu Yu, Jacky Wong, David B. Loveioy, Chelators at the cancer coal face: Desferrioxamine to Triapine and Beyond, Clin. Cancer Res., 2006, v. 12, p. 6876-6883].

The zinc chelator clioquinol, by binding Zn ²⁺ ions, causes apoptosis of human cancer cells [Haijun Yu, Yunfeng Zhou, Stuart E. Lind, Clioquinol targets zinc to lysosomes in human cancer cells, Biochem. J., 2009, v. 417, p. 133-139].

As aldehyde dehydrogenase inhibitors, chelators are used to treat alcoholism [Shian S.G., Kao Y.R., Wu F.Y., Wu C.W., Inhibition of invasion and angiogenesis by zinc-chelating agent disulfiram, Mol. Pharmacol., 2003, v. 64(5), p. 1076-84], as well as in alcoholic cirrhosis of the liver, iron excess anemia, porphyria tarda [Schroterova L., Kaiserova H., Baliharova V., The effect of new lipophilic chelators on the activities of cytosolic reductases and P450 cytochromes involved in the metabolism of antracyclin as antibiotics: in vitro studies, Physiol Res., 2004, v. 53(6), p. 683-691].

The activity of some antioxidants is due to the chelation of transition metal ions (Fe, Cu), which is accompanied by a decrease in metal-dependent lipid peroxidation [Babizhayev M.A., Seguin Marie-C, Gueynej J., Evstigneev R.P., Ageyeva E.A., Zheltuchina G.A., L-Carnosine (alanyl-L -histidine) and carcinine f-alanylhistamine) act as natural antioxidants with hydroxyl-radical-scavenging and lipid-peroxidase activities, Biochem. J., 1994, v. 304, p. 509-516].

The use of antioxidants can promote the resorption of cataracts, eliminate retinal diseases and reduce the need for insulin in diabetics, eliminate skin pigmentation, and also help eliminate the effects of stroke. Chelation is also useful in the treatment of inflammatory diseases such as osteoarthritis, rheumatoid arthritis. [Zelenin K.N., Complexons in medicine, Soros Educational Journal, 2001, vol. 7, no. 1, pp. 45-50].

Chelators can be used in medicine as complexons for transporting and easily removing arsenic, mercury, antimony, cobalt, zinc, chromium, and nickel from the body [Zholnin A.V., Complex compounds, Chelyabinsk: Chelyabinsk State Medical Academy, 2000, p. 28].

Inhibition of botulinum toxin by chelation of zinc ions is known [Anne C, Blommaert A., Thioderivede disulfides as potent inhibitors of botulinum neurotoxin B: implications of zinc interaction, Bioorg. Med. Chem., 2003, v. 11(21), p. 4655-60], in addition, chelation protects against gas gangrene [Zelenin K.N., Complexons in medicine, Soros Educational Journal, 2001, vol. 7, no. 1, pp. 45-50].

Chelation therapy is useful in the treatment of neurodegenerative diseases, in particular Alzheimer's disease, helping to improve memory [Bossy-Wetzel E., Schwarzenbacher R., Lipton S.A., Molecular pathways to neurodegeneration, Nat. Med, 2004, v. 10, p. 2-9]; Parkinson's disease [Kevin J. Barnham, Colin L. Masters, Ashley I. Bush, Neurodegenerative diseases and oxidative stress, Nature Reviews Drug Discovery, 2004, v. 3, p. 205-214]; Wilson's disease [Yu Yu, Jacky Wong, David B. Lovejoy, Chelators at the Cancer Coalface: Desferrioxamine to Triapine and Beyond, Clin. Cancer Res. 2006, v. 12, p. 6876-6883]; Huntington's disease [Whitnall M., Richardson D.R., Iron: a new target for pharmacological interference in neurodegenerative diseases, Semin Pediatr Neurol, 2006, v. 13, p. 186-197]; amyotrophic lateral sclerosis [Kevin J. Burnham, Colin L. Masters, Ashley I. Bush, Neurodegenerative diseases and oxidative stress, Nature Reviews Drug Discovery, 2004, v. 4] and prion diseases [Daniel L. Cox, Jianping Pan, Rajiv R.P. Singh, A Mechanism for Copper Inhibition of Infection Prion Conversion, Biophysical Journal, 2006, v. 91, L11L13]. Chelators prevent cancer [Megan Whitnall, with a wide spectrum of potent antitumor activity that overcomes resistance to chemotherapeutics, PNAS, 2006, v. 103, no. 40, p. 14901-14906].

A significant place among the known chelators is occupied by derivatives of heterocyclic compounds, for example, imidazole, containing imido and amido groups.

In the article by M.A. Podyminogin, V.V. Vlassov, Synthesis of RNA-cleaving molecules mimicking ribonuclease A active center. Design and cleavage of tRNA transcrints, Nucleic Acids Research, 1993, v. 21, No. 25, pp. 5950-5956, a bishistamine derivative of glutaric acid is described, which can serve as a model of the active site of nucleases and exhibits weak activity in the cleavage of RNA molecules.

Elfriede Schuhmann et al., Bis[platinum(II)] and Bis[Palladium (II)] complexes of -Dicarboxylic Acid Bis(1,2,4-triaminobutane-N ⁴ )-Amides, Inorg. Chem., 1995, v. 34, p. 2316-2322, bishistamine derivatives of glutaric and adipic acids are described, which are intermediates for the synthesis of complexes with platinum and palladium:

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n=3-6, 8;

M=Pt, Pd.

A method for the synthesis of N ¹ ,N ¹ -glutarylbis(histamine), including the interaction of histamine dihydrochloride and glutaric acid dichloride in dimethylformamide in the presence of a 4-fold excess of triethylamine, is described in the article by Elfriede Schuhmann et al., Bis[platinum (II)] and Bis[Palladium (II)] complexes of ώ-Dicarboxylic Acid Bis(1,2,4-triaminobutane-N ⁴ )-Amides, Inorg. Chem., 1995, v. 34, p. 23162322.

The authors of the present invention discovered for the first time that the bishistamine derivative of glutaric acid, namely N ¹ ,N ¹ -glutaryl bis(histamine), is capable of forming complexes with metal ions.

Thus, the purpose of the present invention is to obtain biocompatible heterocyclic chelators of metal ions and their use as a medicine for the treatment and/or prevention of various diseases, using the ability of the claimed compounds to chelate metal ions.

The objective of the invention is also to develop simple methods for preparing such compounds using readily available reagents.

Brief description of the invention

The present invention relates to methods for producing compound 2

including:

condensation of a dicarboxylic acid ester of the formula R ₄ OC(O)-CH ₂ -C(O)-OR ₄ , where R4 is C ₁ -C ₆ alkyl, and an amine

when heated, in the presence of an organic solvent;

or comprising reacting a dicarboxylic acid with N-hydroxysuccinimide in the presence of N,N'-dicyclohexylcarbodiimide to produce the corresponding bis-N-hydroxysuccinimide ester, which is condensed with the amine; or reacting a dicarboxylic acid diester with hydrazine hydrate, treating the resulting dihydrazide with sodium nitrite to obtain the corresponding azide, which is condensed with the amine; or heating a solution of an imide formed from a dicarboxylic acid and a corresponding amine in an organic solvent; or reacting the appropriate amine and dicarboxylic acid in 2:1 molar ratios in the presence of a condensing agent.

Proposed methods for preparing the compound of formula 2

are simple to implement, occur under fairly mild conditions, without the formation of by-products, are technologically advanced, and allow one to obtain target products with good yield (up to 82%) and a high degree of purity.

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Detailed description of the invention

As pharmaceutically acceptable salts of compound 2 of the present invention, addition salts of organic acids (for example, formate, acetate, maleate, tartrate, methanesulfonate, benzenesulfonate, toluenesulfonate, etc.), addition salts of inorganic acids (for example, hydrochloride, hydrobromide, sulfate) can be used , phosphate, etc.), salts with amino acids (for example, aspartic acid salt, glutamic acid salt, etc.), preferably hydrochlorides and acetates.

Compound 2 of the present invention can be prepared by a method involving the condensation of a dicarboxylic acid of general formula 11:

R ₄ OC (O) -R ₃ -C (O) -OR ₄ , where R3 represents a -(CR ₂ )n- group, optionally substituted with one or two C1-C6 alkyls, or phenyl, n represents 1,

R4 is C1- _C6 alkyl,

and an amine of the formula by heating, optionally in the presence of a solvent. It is preferable to use dimethyl ether and heat to a temperature of 150-170°C, even more preferably to carry out condensation at boiling.

Diglyme or alcohols can be used as solvents, most preferably isoamyl alcohol.

Another method for preparing compound 2 is a method involving the reaction of a dicarboxylic acid of general formula II:

R ₄ oC (O) -R ₃ -C (O) -OR ₄ , where R3 represents the group -(CH ₂ ) _n -, n represents 1,

R ₄ is hydrogen, with N-hydroxysuccinimide in the presence of N,N'-dicyclohexylcarbodiimide in N,N-dimethyl form mide to give the corresponding bis-N-hydroxysuccinimide ester, general formula IV:

which is condensed with an amine of general formula III:

NH ₂ - (CH ₂ ) ₂ -Ri, where R1 represents imidazolyl.

Cooling to a temperature of 0-5°C is preferable.

Another method for preparing compound 2 is a method involving the reaction of an ether

- 5 045675 dicarboxylic acid of general formula II:

R ₄ oC (O) -R ₃ -C (O) -OR ₄ , where R ₃ represents the group -(CH ₂ ) _n -, n represents 1,

R4 is C1-C6 alkyl, with hydrazine hydrate in an organic solvent to give a bishydrazide of general formula V:

H ₂ N-NH-C (O) -R ₃ -e (O) -NH-NH ₂ , treatment of the bishydrazide with sodium nitrite in an acidic environment at a temperature of about 0°C to obtain a bisazide of general formula VI:

N~-N ⁺ =NC (O) -R ₃ -C (O) -N=N ⁺ -N~, condensation of a bisazide with an amine of general formula III:

NH ₂ - (CH ₂ ) 2-R1, where R1 is imidazolyl, in an organic solvent.

Preferably, alcohols are used as the organic solvent, most preferably isopropanol. The method is simple, but is applicable if the number of methylene units in the original dicarboxylic acid is greater than or equal to three, since the bisazides obtained during the synthesis for acids with a smaller number of methylene groups are unstable.

Another method of the present invention is a method for the preparation of bisamide derivatives of dicarboxylic acids of general formula I, including the reaction of a dicarboxylic acid of general formula II:

R ₄ oC (0) -R ₃ -C (O) -OR ₄ , where R ₃ represents the group -(CH2) _P -, n represents 1, R ₄ represents hydrogen, and an amine of general formula III:

NH ₂ - (CH ₂ ) ₂ -Ri, where R1 represents imidazol-2-yl;

at a molar ratio of 1:2-2.5 in a solution of tetrahydrofuran in the presence of a condensing agent, preferably carbonyldiimidazole.

Compound 2 synthesized by one of the methods of the present invention is administered in an effective amount that provides the desired therapeutic result.

Compound 2 can be administered orally, topically, parenterally, intranasally, inhaled and rectally in unit dosage forms containing non-toxic pharmaceutically acceptable carriers. As used herein, the term parenteral administration means subcutaneous, intravenous, intramuscular or intrathoracic injections or infusions.

Compound 2 may be administered to a patient in doses ranging from 0.1 to 100 mg/kg body weight per day, preferably in doses ranging from 0.25 to 25 mg/kg one or more times per day.

It should be noted that the specific dose for each individual patient will depend on many factors, including the potency of the compound used, age, body weight, gender, the patient's general health and diet, the time and method of administration of the drug, the rate of its elimination from the patient. body, the specific combination of drugs used, and the severity of the disease in the individual being treated.

A detailed description of the preparation of compound 2 of the present invention and activity studies is presented in the following examples, intended to illustrate preferred embodiments of the invention and not to limit its scope.

Examples of synthesis of compound 2.

Means and methods.

The identity of the resulting compounds is checked by TLC on Kieselgel 60 F254 plates (Merck, Germany) in a solvent system: pyridine-acetic acid-water (20:6:11) system A, A:ethyl acetate 3:1 (1), chloroform-methanol 9:1 (2).

Electrophoresis on paper (electrophoresis paper of the Kondopoga pulp and paper mill, 120x320 mm) is carried out in a buffer with pH 5.1 of the composition pyridine-acetic acid-water 12:10:1000 in a chamber (150x320x150 mm) with a gradient of 15 V/cm for 1.5 h.

Chromatograms and electropherograms are developed with chloro-tetramethylbenzidine reagent and Pauli reagent.

The melting point is determined using a PTP device (laboratory instrument plant, Russia, Klin).

FTIR spectra were recorded in KBr pellets on a Magna 750 instrument (Nicolet (USA)).

1H-NMR spectra are recorded on an AMX-400 (Germany), Bruker DPX-400 (Germany) instrument.

High-resolution mass spectra are obtained on a time-of-flight mass spectrometer using the

- 6 045675 matrix laser desorption ionization using 2.5 dihydroxybenzoic acid as a matrix, on an Ultraflex device (Bruker, Germany).

LC/MS system for the analysis of multicomponent mixtures Shimadzu Analytical HPLC SCL10Avp, mass spectrometer PE SCIEX API 165 (150), (Canada).

Analytical reverse-phase HPLC was carried out on a device: HPLC Shimadzu chromatograph under conditions: column Luna C18 (2) 100 A, 250x4.6 mm (ser. 599779-23), elution gradient in the system phosphate buffer solution pH 3.0: methanol ( conditions A). On the device, a Beckman (USA) System Gold chromatograph with a UV detector (λ=220 nm), Gemini C-18 column, 150x2.0 mm Phenomenex, mobile phase gradient in 0.05 M phosphate buffer (pH 3.0) 90% MeCN in water, elution rate 0.25 ml/min, injection of 10 μl (conditions B).

Example 1

Bis-1,3-(N ^β -histaminyl)malonic acid; (N,N'-bis-[2-(1H-imidazol-4-yl)ethyl]npropanediamide) (compound 2)

To 6.4 g (0.039 mol) of malonic acid diethyl ester, add 9.0 g (0.081 mol) of histamine and heat at 170°C for 2.5-3 hours until the release of ethyl alcohol vapor stops. The completeness of the reaction is monitored by TLC or electrophoresis. Then the reaction mass is suspended in 20 ml of water and left for 72 hours at +4°C. The product is separated, washed with isopropyl alcohol, and dried. Yield 5.0 g (44%). R _f 0.41 (1). E+57 mm. T.pl. 187-188°C. Spectrum ¹ H-NMR (D2O): δ, ppm: 2.74-2.78 (t, 4H, 3-SCH-NA), 3.15 (s, 2H, CH-Mal), 3, 41-3.44 (t, 4H, a-CH ₂ -HA), 6.78 (s, 2H, 5-CH-Im), 7.66 (s, 2H, 2-CH-Im). IR-Fourier spectrum (in the table KBr, v, cm ^-1 ): 1643 (v C=O amide I), 1574 (δ NH amide II), 1426 (-CH2-CO-). Found, %: C 53.24, H 6.51, N 28.56. C13H18N6O2. Calculated, %: C 53.78, H 6.25, N 28.95.

Study of the chelating ability of the described compounds.

The proposed compounds of general formula I, as shown by further research, have the ability to complex or chelate metal ions. They have several functional groups that can act as electron donors during complex formation, for example, a carboxyl group, imido-, amido groups, and are ligands that specifically interact with metal ions, for example, with zinc, copper, iron, calcium, magnesium ions.

An important characteristic of the ability of a ligand to form complexes is the dissociation constants (pk _n ) of the compounds under study in an aqueous solution. The pk _n values are determined using the potentiometric titration method. Calculation of dissociation constants is carried out according to the Schwarzenbach method [Grinberg A.A., Introduction to the chemistry of complex compounds, ed. 4th, revised, L., Chemistry, 1971].

Methods of pH-potentiometric titration.

Titration was carried out on a setup using a laboratory type ion meter I 120.1. The created galvanic cell consisted of two electrodes: an indicator glass and a silver chloride reference electrode. pH values were determined with an accuracy of ±0.2.

Initial 0.05 M solutions of metal ion salts M ^z+ were prepared from zinc nitrates (Zn(NO3) ₂ 6H ₂ O), calcium (Ca(NO3) ₂ 4H ₂ O), copper sulfate (CuSO4 5H ₂ O), magnesium chloride (MgCl ₂ 6H ₂ O) and Mohr's salt ((NH4) ₂ Fe(SO4) ₂ 6H ₂ O). Standardization of the initial solutions of M ^z+ salts was carried out using complexometric titration with Trilon B (M ^z+ =Zn ²⁺ , Cu ²⁺ , Mg ²⁺ , Ca ²⁺ ), spectrophotometrically at 490 nm using o-phenanthroline (M ^z+ =Fe ²⁺ ).

A typical method for determining stepwise acid dissociation constants (k _b . . ., k _n ) by pHmetric titration using the Schwarzenbach method.

A weighed portion of the compound under study (3x10-4 mol) was dissolved in 15.0 ml of a 0.5 M aqueous solution of KNO ₃ . The resulting 0.02 M solution was titrated with vigorous stirring with a 0.05 M aqueous solution of NaOH or HCl. The amount (V, ml) of the consumed titrant and the pH of the solution were recorded at each titration point. The titration step was 0.5 ml, near the equivalence point - 0.2 ml. Titration was carried out until the pH of the solution was 11.0-11.5. From the titration curve pH=f(a), the pH value of the solution corresponding to a=0.5 and/or a=1.5 was determined, and the number of added g-equivalents of the titrant was determined per 1 mol of the titrated substance.

The results of determining the acid dissociation constants [pk _n ] using the Schwarzenbach method for the compounds under study are presented in table. 2.

table 2

pk values of compound 2 in aqueous solution, calculated by the Schwarzenbach method (C 0.02 M, ionic ______________________ strength of solution 0.5 (KNO ₃ ), 22°C)______________________

Connection number pki rk ₂ 2 7, 11 ⁽¹ > 11.27 ⁽² >

⁽¹⁾ - titration with aqueous 0.05 M HCl solution.

⁽²⁾ - titration with an aqueous 0.05 M NaOH solution.

Taking into account such parameters as the amount of the test substance required for potentiometric titration, the methodology for its implementation and calculation of constants, the most suitable, informative and simple is the Bjerrum method [Galaktionov, M.A. Chistyakov, V.G. Sevastyanov et al.

Stepwise stability constants of complexes of group III B elements and lanthanides with acetylacetone in aqueous solution and the solubility products of their triacetylacetonates, Zh. Phys. Khim., 2004, vol.

78, No. 9, p. 1596-1604].

The method is based on the concept of a stepwise process of complex formation. The main assumption of Bjerrum's method is the assumption that only mononuclear complexes are formed. Schematically, the complex formation process can be described as follows:

M+L^ML K!=[ML]/[M] [L]

ML _n _!+L^ML _n K _n = [ML _n ] / [ML^] [L]

According to Bjerrum's method, the compound under study is titrated twice with NaOH solution: in the absence and in the presence of a metal ion. Titration is carried out at a high constant concentration of an indifferent electrolyte, ensuring a constant ionic strength of the solution.

For these purposes, highly soluble salts are used, for example, potassium nitrate. Concentration stepwise stability constants ( _Kn ) are experimentally found. In addition, it is possible to obtain information about the composition of the resulting complexes, namely, the maximum possible number of attached ligands (n).

A typical method for determining stepwise stability constants of complexes by pH-metric titration using the Bjerrum method.

A weighed portion of the compound under study (3x10'4 mol) was dissolved in 14.0 ml of a 0.5 M aqueous solution of KNO ₃ . With vigorous stirring, 1.0 ml (5x10'4 mol) of 0.05 M aqueous solution of salt M ^z+ was added. Systems with a ratio of M ^z+ to L of 1:6 were studied. The pH values of the solution were recorded in the presence of the ligand and metal ions in the solution together. Titration of the mixture was carried out with a 0.05 M aqueous solution of NaOH over a wide pH range (up to pH values of 11.0-11.5). The amount of titrant consumed (VNaon, ml) and the pH of the solution were recorded at each titration point. At the moment of formation of a precipitate, turbidity of the solution or change in its color, the pH value, the nature of the change and the volume of the NaOH solution used for titration were recorded. The titration step is 0.25 ml. Using the Bjerrum curve ⁿ =f(pA) for each half-integer value of the formation function ⁿ =n-0.5, logKn was determined.

Currently, the Bjerrum method is often used to study complex formation. This method involves the determination of two parameters - the concentration of the free ligand under equilibrium conditions - [L'] and the formation function ⁿ , which is the average number of ligands included in the complex. Thus, at any moment of titration, using experimental data, it is possible to calculate [L'] (namely, -log[L']=pA) and according to equation (1) - ⁿ . When the ligand has several dissociating groups, then in equation (1) K _L corresponds to the value of the dissociation constant that has the largest pk value.

From the constructed Bjerrum curve (formation curve) ⁿ =f(pA) using equation (2) for each half-integer value of the formation function ⁿ =n-0.5, Kn is found. Thus, the stepwise stability constant will be equal to the inverse concentration of the free ligand at point ⁿ =n-0.5. Accordingly, the higher the Kn value, the more stable the complex compound (chelate) is.

c _L — - [L“] (10-ri _{+ K} ) οθ „ - K _L n _L ^c m ^z+ Yu ^pH ' ⁿ M ^z+

K _VC A = (2)

ILL J where and ^c M ^z+ are the total concentrations of the ligand and metal present in the solution, mol/l;

[L’] - concentration of free ligand ions, mol/l;

KL is the acid dissociation constant of the ligand;

^advlnun - volume of NaOH solution (C ⁰ _NaOH , mol/l) at any time of titration, added to the titrated mixture of M ^z+ and L, l;

n _L , is the amount of ligand substance and salt M ^z+ in the titrated solution, mol.

The logK1 values found using the Bjerrum method for complexes of the studied compounds with divalent metal ions are presented in Table. 3, 4. The choice of the ratio of M ^z+ to L, equal to 1:6, is due to the availability of data on the maximum possible coordination number for Zn(II) and Fe(II), equal to six, and for Cu(II) - equal to four [Claudia A Blindauer, M. Tahir Razi, Simon Parsons, Peter J. Sadler, Polyhedron, 2006, v. 25, p. 513-520].

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Table 3

The first stability constant of complexes of the 1:1 composition of compound 2 with divalent metal ions is logKl, found by the Bjerrum method (aqueous solution, CL = 0.02 M, ratio of M ^z+ to L 1:6, ionic strength 0.5 (KNO3), 22°С)

Connection number The first stability constant of the 1:1 complexes of the studied compounds with divalent metal ions is 1dK ₂ Zn(II) Cu(II) Fe(II) Her (III) Md (II) Ca(II) 2 4, 84 4, 17 5, 08 5.29 2.59 2, 06

Table 4

Stepwise stability constants of complexes of composition 1:1 of compound 2 with zinc ions, found by the Bjerrum method (aqueous solution, CL = 0.02 M, ratio of M ^z+ to L 1:6, ionic strength of solution 0.5 ___________________________________(KNO3), 22 °C)_________________________________

Connection number Stepwise stability constants for complexes of the 1:1 composition of the studied compounds with zinc ions First stability constant, logKi Second stability constant, 1dK ₂ Third stability constant, 1dK ₃ 2 4, 84 4.50 2, 60

Thus, the studies have shown that the tested compounds, derivatives of bisamides of dicarboxylic acids, are effective complexing agents, for most of which high values of logK1>5 were found with respect to transition metal ions. In this case, a slightly increased complexing ability of the proposed compounds of general formula I with respect to iron ions is observed.

Claims (8)

1. Method for preparing the compound of formula 2: involving the condensation of a dicarboxylic acid ester of the formula: R ₄ OC(O)-CH ₂ -C(O)-OR ₄ , where R4 is C1-C ₆ alkyl, and ^{H H2N} \^\/ ^N x X) amine ' when heated, in the presence of an organic solvent. 2. The method according to claim 1, in which diglyme or alcohols are used as a solvent and heating is carried out to 150-170°C. 3. The method according to claim 1, in which condensation is carried out in a solution of isoamyl alcohol at boiling. 4. Method for preparing the compound of formula 2: involving the interaction of a dicarboxylic acid of the formula: R ₄ OC(O)-R3-C(O)-OR ₄ , where R3 represents a -(CH ₂ ) _n - group; n is 1; - 9 045675 R4 is hydrogen, with N-hydroxysuccinimide in the presence of N,N'-dicyclohexylcarbodiimide in N,N-dimethylformmide to give the corresponding bis-N-hydroxysuccinimide ester of formula: where R3 represents a -(CH ₂ ) _P - group; η represents 1, which is condensed with an amine of the formula: NH ₂ -(CH ₂ ) ₂ -R _b where Ri represents imidazolyl. 5. The method according to claim 4, where condensation is carried out by cooling to a temperature of 0-5°C. 6. Method for preparing the compound of formula 2: involving the interaction of a dicarboxylic acid ester of the formula: R4O-C(O)-R ₃ -C(O)-OR4, where R ₃ represents a -(CH ₂ ) _P - group; η represents 1; R4 is C _G C ₆ alkyl, with hydrazine hydrate in an organic solvent to give a bishydrazide of the formula: H ₂ N-NH-C(O)-R ₃ -C(O)-NH-NH ₂ , treating the bishydrazide with sodium nitrite in an acidic environment at a temperature of about 0°C to obtain a bisazide of the formula: N'-N ⁺ =NC(O)-R ₃ -C(O)-N=N ⁺ -N', condensation of an azide with an amine of the formula: NH ₂ -(CH ₂ ) ₂ -R _b where R _l represents imidazolyl, in an organic solvent. 7. The method according to claim 6, in which alcohols, preferably isopropanol, are used as an organic solvent. 8. Method for preparing the compound of formula 2: involving the interaction of a dicarboxylic acid of the general formula: R ₄ OC(O)-R ₃ -C(O)-OR4, where R ₃ represents a -(CH ₂ ) _{P_} group; η represents 1; R4 represents hydrogen, and an amine of the formula: NH ₂ -(CH ₂ ) ₂ -R _b where R _l represents imidazol-2-yl, at a molar ratio of 1:2-2.5 in the presence of a condensing agent - carbonyldiimidazole.