Synthesis and properties of 2-(4-phenyl-5-(((5-phenylamino- 1,3,4-thiadiazole-2-yl)thio)methyl)-1,2,4-triazole-3-yl)thio)ethanoic acid and its salts

Analysis of the literature over the past decade has shown that the chemistry of 1,2,4-triazole and 1,3,4-thiadiazole attracts considerable interest from scientists around the world because of the many valuable properties of compounds of this class. Bibliosemantic analysis shows that the nuclei of 1,2,4-triazole and 1,3,4-thiadiazole are fragments of a number of known drugs and biologically active compounds. That is why the synthesis and study of physical-chemical, biological properties of salts and acids containing these heterocyclic fragments are quite relevant both from a theoretical and practical point of view.


Актуальные вопросы фармацевтической и медицинской науки и практики. 2020. Т. 13, № 3(34). С. 330-336
An analysis of the literature sources over the last decade has shown that the chemistry of 1,2,4-triazole and 1,3,4-thiadiazole attracts significant interest from scientists around the world because of the many valuable properties of compounds of this class [1,2]. Bibliosemantic analysis shows that the nuclei of 1,2,4-triazole and 1,3,4-thiadiazole are fragments of a number of known drugs and biologically active compounds [3,4]. That is why the synthesis and study of physical-chemical, biological properties of salts and acids containing these heterocyclic fragments are quite relevant both from a theoretical and practical point of view [5,6].

2-((4-Phenyl-5-((5-phenylamino-1,3,4-thiadiazole-2-yl)thio) methyl)-1,2,4-triazole-3-yl)thio)ethanoic acid with organic bases.
A mixture of 0.01 mol of the starting carbo xylic acid, 15-20 ml of water and 0.012 mol of the corresponding organic base (diethylamine, diethylmonoethanolamine, morpholine, piperidine) was heated for 1 hour in a water bath, filtered, the solvent was evaporated to a total volume. The residue was added to acetone or propan-1-ol. The precipitated white crystalline substances were recrystallized from ethanol. The product was soluble in water, sparingly soluble in organic solvents. (Fig. 2). A mixture of 0.01 mol of the starting carboxylic acid and 0.01 mol of sodium or potassium hydroxide in 30 ml of water was heated in a water bath for 10-15 minutes, filtered and evaporated to its original volume and precipitated by the addition of acetone. It was obtained white crystalline substances, sparingly soluble in organic solvents. The compound was recrystallized from ethanol for analysis. (Fig. 2). A mixture of 0.02 mol of the starting carboxylic acid, 25 ml of water and 0.01 mol of magnesium oxide or calcium carbonate or zinc sulphate, respectively, was heated to dissolve the precipitate, filtered and the filtrate was evaporated. The compounds were recrystallized from water. The resulting product was a white solid, sparingly soluble in water, sparingly soluble in organic solvents.

Results
The structure and individuality of the synthesized compounds were confirmed by a package of modern physical-chemical methods of analysis.
For example, in the IR spectra of all synthesized compounds there were absorption bands -C=N groups at 1607-1582 cm -1 , C-S groups -at 702-685 cm -1 , as well as symmetric and asymmetric absorption bands characteristic of carboxylic acid salts containing COO groups in the range of 1371-1342 cm -1 and 1597-1525 cm -1 , respectively. The IR spectra of salts also were contained absorption bands at 1508-1473 cm -1 , which indicates the presence of aromatic substituent's in their structure. For salts of organic bases there are wide absorption bands of primary and secondary amines in the range 3053-2907 cm -1 or 2712-2258 cm -1 and deformation oscillations in the range 1610-1563 cm -1 .
The IR spectrum of the ammonium salt were contained the absorption band of the valence vibrations of the ammonium group at 3435 cm -1 .

1
H NMR spectra of salts were confirmed by signals of the corresponding protonated amines. For example, in the spectrum of the diethylammonium salt, multiplets were observed in the intervals 3.12-3.01 and 1.40-1.33 ppm, respectively. In the spectrum of the diethylmonoethanolammonium salt there were two triplets at 4.03 ppm and 3.46 ppm, a singlet at 7.08 ppm, and an OH group signal in the form of a triplet at 4.16 ppm. The spectrum of the morpholine salt had a characteristic set of signals of the protonated cation of morpholine in the form of two multiplets at 3.96-3.83, 3.38-3.30 ppm and a singlet at 7.11 ppm. The piperidinium salt was characterized by proton signals of organic bases in the form of multiplets 3.15-3.11 ppm, 1.93-1.76 ppm, 1.55-1.42 ppm and 1.50 ppm and singlet 7.04 ppm. The fact remains that for many years the standard drugs Diclofenac sodium and Ketoconazole are used to treat inflammatory processes and fungal lesions [8][9][10].
Therefore, in the next stage of our work, we predicted the probability of anti-inflammatory activity among the synthesized substances using the in silico (molecular docking) method [11,12].
Molecular docking was performed using Autodock 4.2.6. Macromolecules from Protein Data Bank (PDB) were used as biological targets, namely COX-1 enzyme in complex with diclofenac and lanosterol-14α-demethylase in complex with ketoconazole (Tables 1, 2). All programs used in the screening process are publicly available [13,14].

Discussions
As a result of the molecular docking for the synthesized salts of 2-((4-phenyl-5-(((5-phenylamino-1,3,4-thiadiazole-2-yl) thio)methyl)-1,2,4-triazole-3-yl)-thio)ethanoic acid established a promising level of anti-inflammatory effect. It should be noted that the conversion of the starting acid into a salt as a result of interaction with organic or inorganic bases leads to an increase in the likelihood of anti-inflammatory activity.
Regarding the results of the study of the affinity of the synthesized compounds to the active site of lanosterol-14α-demethylase, it should be noted that there is an increase in the energy of interaction with the enzyme as a result of the transition from acid to its salts.
2. The optimal conditions for the synthesis of the target reaction products were established.