Towards Property Profiling: SYNTHESIS and SAR Probing of New Tetracyclic Diazaphenothiazine Analogues

A series of new tertiary phenothiazine derivatives containing a quinoline and a pyridine fragment was synthesized by the reaction of 1-methyl-3-benzoylthio-4-butylthioquinolinium chloride with 3-aminopyridine derivatives bearing various substituents on the pyridine ring. The direction and mechanism of the cyclization reaction of intermediates with the structure of 1-methyl-4-(3-pyridyl)aminoquinolinium-3-thiolate was related to the substituents in the 2- and 4-pyridine position. The structures of the compounds were analyzed using 1H, 13C NMR (COSY, HSQC, HMBC) and X-ray analysis, respectively. Moreover, the antiproliferative activity against tumor cells (A549, T47D, SNB-19) and a normal cell line (NHDF) was tested. The antibacterial screening of all the compounds was conducted against the reference and quality control strain Staphylococcus aureus ATCC 29213, three clinical isolates of methicillin-resistant S. aureus (MRSA). In silico computation of the intermolecular similarity was performed using principal component analysis (PCA) and hierarchical clustering analysis (HCA) on the pool of structure/property-related descriptors calculated for the novel tetracyclic diazaphenothiazine derivatives. The distance-oriented property evaluation was correlated with the experimental anticancer activities and empirical lipophilicity as well. The quantitative shape-based comparison was conducted using the CoMSA method in order to indicate the potentially valid steric, electronic and lipophilic properties. Finally, the numerical sampling of similarity-related activity landscape (SALI) provided a subtle picture of the SAR trends.

SYNTHETIC APPROACHES TO HYDROGENIZED PYRIDYL[b]AZEPINE AND THEIR BENZENELYLATED ANALOGUES

Pyrido[b]azepines are represented in the literature by four types of isomeric structures: pyrido[3,2-b] azepines, pyrido[2,3-b]azepines, pyrido[3,4-b] azepines and pyrido[4,3-b ]azepines. They belong to the structural analogues of 1-benzazepine - an attractive class of heterocycles with a strong pharmacological profile. They are also used as important molecular platforms in the construction of bioactive compounds. Analysis of the literature has shown that compounds that contain the pyrido[b]azepine fragment demonstrate antiviral, antimicrobial, and antitumor activity. They are knownas effective inhibitors of R1P1 kinase, ubiquitin- specific proteases (USPS), cyclin-dependent kinase (CDKS), and glycogen synthase kinase 3 (GSK-3), TRPM8 protein, and angiotensin I type 2 (AT2) receptors. Over the last decade, promising pharmacological properties of pyrido[b]azepine derivatives stimulated the development of fundamentally new methods of their synthesis as well as the improvement of known synthetic approaches. In general, among the various methods for the synthesis of hydrogenated pyrido[b] azepines and their benzanelated analogues, priority is currently given to approaches that include the formation of an azepine cycle via the intermolecular formation of C-N and C-C bonds. These mainly include catalytic cyclizations using cobalt, palladium, and rhodium compounds. Reactions of intramolecular radical difluoromethylarylation and diauryl peroxide-initiated radical azepine analelenization of the pyridine fragment are also of great importance. An interesting method for the synthesis of pyrido [2,3-b] azepin-5-one derivatives was developed on the basis of the Friedel-Crafts intramolecular cycloalkylations reaction.

Synthetic Approaches to the Bifunctional Chelators for Radio­nuclides Based On Pyridine-Containing Azacrown Compounds

Synthetic ways to introduce functional groups (CO2Me, CO2H, OCH2CO2H, OCH2C≡CH, CH2OH, CH2Cl, CH2N3) into the pyridine ring of pyridine-containing azacrown compounds are described. These groups were introduced at position-4 of the pyridine ring, while keeping the macrocyclic carboxylate groups available for metal chelation. The derivatives were obtained by macrocyclization reaction of 4-substituted, trimethyl pyridine-2,4,6-tricarboxylate or by modification of methyl ester group in pyridine fragment of macrocycles. Obtained derivatives can be applied for preparing radiotherapeutic agents by conjugation to different vector biomolecules for targeted drug delivery to cancer cells without damaging healthy tissue.

SYNTHETIC PYRIDINE SUBSTITUTED AMINO ACIDS AND THEIR DERIVATIVES

This paper reports on the synthesis of new derivatives of ε-aminocaproic and γ-aminobutyric acid modified with a pyridin-2-yl substituent at the ω-position of the main chain. The hemostatic activity of both ε-aminocaproic acid itself and its various synthetic analogues is widely known. Likewise, numerous γ-aminobutyric acid derivatives are strong neurotransmitters extensively used in the treatment of the nervous system disorders. No less popular are biologically active substances containing a pyridine or piperidine fragment; among which there are antibiotics, antimalarial, anti-sclerotic and antiallergic drugs, as well as anti-depressants and analgesics. Therefore, the introduction of the pyridine fragment into the amino acid structures is interesting in terms of their potential biological activity investigation. So, a method for the synthesis of 5-amino-5-(pyridin-2-yl)pentanoic and 6-amino-6-(pyridin-2-yl)hexanoic acid has been developed by us. The proposed scheme is based on the available reagents using. The key stage is the Schmidt rearrangement of 2-(pyridin-2-yl)cyclopentanone and 2-(pyridin-2-yl)cyclohexanone, previously synthesized from pyridine N-oxide and cycloalkenyl morpholinide. For synthesized pyridine substituted cycloalkanones according to NMR spectroscopy, the presence of keto-enol tautomerism was established. As a result of Schmidt rearrangement, lactams (2-(pyridin-2-yl)piperidone and 2-(pyridin-2-yl)azepanone) are formed, and the last ones had been hydrolyzed in an acidic medium to open the lactam cycle. Thus, 5-amino-5-(pyridin-2-yl)pentanoic and 6-amino-6-(pyridin-2-yl)hexanoic acid were isolated as hydrochlorides and the hydrochlorides were converted to the zwitterion form using propylene oxide. The first stage of the developed scheme (preparation of pyridylalkanones) occurs in rather low yields, about 35 %. But, after the rearrangement, hydrolysis and the formation of zwitterion do not cause difficulties and are characterized by high yields. Consequently, the proposed synthetic sequence is preparatively advantageous.