Vol. 15 No. 1(57) (2017)
Published:
2017-03-23
Full Issue
Original Researches
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Azolo[1,4]diazepines: the methods of synthesis and structural modification
The literature relating to the methods of synthesis and chemical transformations of azolo[1,4]diazepines (pyrazolo-, imidazo-, triazolo-, isoxazolo-, oxazolo-, isothiazolo- and thiazolodiazepines) currently known have been generalized and systematized. Their role as important substances for the design of compounds with a great pharmacological potential has been noted. The methods of synthesis of pyrazolo[3,4-e][1,4]diazepines, pyrazolo[4,3-e][1,4]diazepines and tri- and tetracyclic pyrazolo[1,4]diazepines based on formation of the diazepine ring in most cases due to transformations of multifunctional pyrazole derivatives have been described in detail. A significant emphasis is focused on the structural functionalization of pyrazolo[1,4]diazepines; this functionalization is a powerful tool to design attractive synthetic and biological derivatives. On the examples of 7-hydroxypyrazole[3,4-e][1,4]diazepines the effect of the reaction conditions, electronic and steric parameters, which control the processes of functionalization of the diazepine nucleus with SH-, NH- and C- nucleophilic reagents, is described. The synthetic potential of 7-arylpyrazole[4,3-e][1,4]diazepin-4-ones as key structures for their direct functionalization in position 4 with chloro-, methylthio-, amino- and hydrazino groups is shown. The methods of preparation and some chemical transformations of imidazo[1,4]diazepines, in particular imidazo[4,5-e][1,4]diazepin-8-ones and 5,8-diones, which in recent years attract great attention of researchers, have been analyzed.
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Fragment-based drug design (FBDD)
Fragment-based drug design (FBDD) is one of the modern techniques used for developing new drugs, and an alternative to the widely used high throughput screening. The main methodological approaches of FBDD, as well as the methods of optimization for the identified “fragments“ when transferring them to the drug-like molecules have been described. The basic principles of the biophysical methods for analysis of the fragment – bio-target complexes and their application have been shown. Advantages and disadvantages of such methods as fluorescence-based thermal shift, NMR-spectroscopy, mass spectrometry, surface plasmon resonance are discussed. The most informative and efficient tool for the complex screening is X-ray crystallography. The main approaches to development of the pharmacologically active molecules based on the identified fragments, namely the methods of “fragment merging”, “fragment linking” and “fragment growing”, are given. The prospects and importance of the given method has been confirmed by the specific examples of drug candidates and the antitumor drug Vemurafenib approved and developed using FBDD. -
The study of calixarenes complexation with phenols by RP HPLC
The Host-Guest complexation of octakis(diphenoxyphosphoryloxy)tetramethylcalix[4]resorcinarene, 5,17-bis-(N-tolyliminomethyl)-25,27-dipropoxycalix[4]arene and 5,11,17,23-tetrakis(diisopropoxyphosphonyl)-25,26,27,28-tetrapropoxycalix[4]arene with a series of 11 phenols (phenol, p-fluorophenol, p-chlorophenol, p-bromophenol, pyrogallol, p-cresol, p-aminophenol, p-nitrophenol, salicylic aldehyde, guaiacol and veratrole) has been studied by the high-performance liquid chromatography (RP HPLC) method. Chromatographic characteristics and log P of industrial phenols have been determined. Using the relationship of the phenol retention factor k’ vs the calixarene concentration in the mobile phase the stability constants of the supramolecular complexes KA (29-331 M-1) have been determined. The stability constants of the calixarene complexes show that the Host-Guest interaction strongly depends on the nature of the substituents in the Host and Guest molecules. Calixresorcinarene functionalized by diphenoxyphosphoryl groups and calixarene containing tolyliminomethyl groups formed more stable complexes with some phenols compared to calixarene functionalized by diisopropoxyphosphonyl groups. In accordance with the molecular modeling data the complexation does not change the C2v flattened-cone conformation of the calixarene skeleton. The Host-Guest complexes are stabilized by the intermolecular hydrogen bonds of phenolic OH groups with oxygen atoms of P = O groups at the upper rim, and OH groups at the lower rim of the macrocycle. Hydrophobic interactions also participate in the complexation.
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Synthesis and the diuretic activity of 8-aminosubstituted of 7-(2-hydroxy-3-p-metoxyphenoxypropyl-1)-3-methylxanthine
It has been found that natural xanthines, as well as their synthetic analogs, possess the diuretic effect. Analysis of the literature proves that there is a great opportunity of applying synthetic derivatives of N-methylated xanthines as potential diuretics.
Aim. To develop preparative methods of the synthesis of 8-aminosubstituted of 7-(2-hydroxy-3-p-metoxyphenoxypropyl-1)-3-methylxanthine and study their physical, chemical and biological properties.
Results. The synthesis of a series of 8-aminosubstituted of 7-(2-hydroxy-3-p-metoxyphenoxypropyl-1)-3-methylxanthine was carried out. According to the results of the biological testing the compounds synthesized belong to the toxicity of class IV. 7-(2-Hydroxy-3-p-methoxyphenoxypropyl-1)-8-(furyl-2-methylamino)-3-methylxanthine xanthine shows the highest diuretic activity, and hence, requires a more in-depth study since it is twice more active than hydrochlorothiazide. It should be emphasized that all compounds synthesized exhibit a marked diuretic effect.
Experimental part. 8-Bromo-7-(2-hydroxy-3-p-methoxyphenoxypropyl-1)-3-methylxanthine was obtained by heating 8-bromo-3-methylxanthine with p-methoxyphenoxymethyloxirane in butanol-1 and in the presence of N,N-dimethylbenzylamine. 8-Aminosubstitutied of 7-(2-hydroxy-3-p-metoxyphenoxypropyl-1)-3-methylxanthine was obtained by boiling of bromoalcohol with the primary and secondary amines. The structure of the compounds synthesized was unambiguously confirmed by NMR-spectroscopy. The acute toxicity of the compounds obtained was studied by Kerber method. The study of the diuretic activity of the compounds was carried out using Ye. Berkhin method. Hydrochlorothiazide was used as a reference substance.
Conclusions. Simple methods for the synthesis of 8-amino-7- (2-hydroxy-3-p-methoxyphenoxypropyl-1)-3-methylxanthines have been developed. The structure of the compounds synthesized has been confirmed by the method of NMR 1H-spectroscopy. The acute toxicity and the diuretic activity of the compounds obtained have been studied.
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The presentation of regioselectivity of 1-ethyl-3-[4-(6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[4,3-а]azepin-3-yl)phenyl]thiourea cyclization with α-bromoketone
An important step in creation of potential drugs is to confirm the structure of the compounds synthesized. This requires the use of modern physical and physico-chemical methods of research. Nowadays a promising scientific direction for searching biologically active substances is the study of 2-R-imino-1,3-thiazoline derivatives.
Aim. To study regioselectivity of the cyclization reaction of 1-ethyl-3-[4-(6,7,8,9-tetrahydro-5Н-[1,2,4]triazolo[4,3-а]azepin-3-yl)phenyl]thiourea with 2-bromo-1-phenylethanone.
Results. The true structure of the interaction product was determined by the methods of 1H NMR spectroscopy and X-ray analysis. Quantum chemical calculations of the electronic structure, geometry and thermodynamic parameters of the initial thiourea three tautomers were given. Activating energy of tautomer 1A belower than 1B one, the state of 1B has modest lower relative energy, consequently tautomer 1A is more credible state. Thus, the conclusion can be made that the reaction will proceed by 1-1A-3A.
Experimental part. Quantum chemical calculations of the electronic structure, geometry and thermodynamic parameters of the initial thiourea three tautomers were determined by the density functional theory (DFT) methods using the GAUSSIAN W09 computer program. The effect of the solvent was considered within the framework of polarized continuum model (PCM).
Conclusions. Based on the physico-chemical studies and quantum chemical calculations of the reaction cyclization direction the conclusion has been made that the cyclization reaction of 1-ethyl-3-[4-(6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[4,3-а]azepin-3-yl)phenyl]thiourea 1 with 2-bromo-1-phenylethanone 2 is regioselective, and it leads to formation of more thermodynamically advantageous (stable) isomer 3A.
