scholarly journals Oxidative Photocyclization of Aromatic Schiff Bases in Synthesis of Phenanthridines and Other Aza-PAHs

2020 ◽  
Vol 21 (16) ◽  
pp. 5868
Author(s):  
Martin Kos ◽  
Jaroslav Žádný ◽  
Jan Storch ◽  
Vladimír Církva ◽  
Petra Cuřínová ◽  
...  
Keyword(s):  
Schiff Bases ◽  
Reaction Rate ◽  
Potential Method ◽  
Biologically Active ◽  
Aromatic Rings ◽  
Order Of Magnitude ◽  
Substituent Constants ◽  
Aromatic Imines ◽  
Aromatic Systems ◽  
Electron Donating Groups

The oxidative photocyclization of aromatic Schiff bases was investigated as a potential method for synthesis of phenanthridine derivatives, biologically active compounds with medical applications. Although it is possible to prepare the desired phenanthridines using such an approach, the reaction has to be performed in the presence of acid and TEMPO to increase reaction rate and yield. The reaction kinetics was studied on a series of substituted imines covering the range from electron-withdrawing to electron-donating substituents. It was found that imines with electron-withdrawing substituents react one order of magnitude faster than imines bearing electron-donating groups. The 1H NMR monitoring of the reaction course showed that a significant part of the Z isomer in the reaction is transformed into E isomer which is more prone to photocyclization. The portion of the Z isomer transformed showed a linear correlation to the Hammett substituent constants. The reaction scope was expanded towards synthesis of larger aromatic systems, namely to the synthesis of strained aromatic systems, e.g., helicenes. In this respect, it was found that the scope of oxidative photocyclization of aromatic imines is limited to the formation of no more than five ortho-fused aromatic rings.

scholarly journals Synthesis and Evaluation of Schiff Bases of 4-Amino-5-(chlorine substituted phenyl)-4H-1,2,4-triazole-3-thione as Antimicrobial Agents

2020 ◽  
Vol 41 (1) ◽  
pp. 26-35
Author(s):  
Kishor Devkota ◽  
Govinda Pathak ◽  
Bhushan Shakya
Keyword(s):  
Schiff Base ◽  
Schiff Bases ◽  
Antimicrobial Agents ◽  
Triazole Ring ◽  
Antimicrobial Activities ◽  
Biologically Active ◽  
Spectral Techniques ◽  
Schiff Base Derivatives ◽  
Bacteria And Fungi ◽  
Different Strains

Triazole ring system has attracted a continuously growing interest of synthetic organic chemists and those dealing with the medicinal compounds due to its versatile potential to interact with biological systems. Schiff bases are also considered as one of the most biologically active compounds.  The aim of the present study was to synthesize new Schiff bases bearing triazole nucleus and to assess their antimicrobial activities. Four new Schiff base derivatives of 1,2,4-triazole-3-thione were synthesized by combining two different pharmacophores viz. triazole nucleus and Schiff base moiety and were characterized by spectral techniques (UV, FT-IR, and NMR). The Schiff bases were evaluated for antibacterial (Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae) and antifungal (Candida albicans) activities. The synthesized compounds exhibited good to moderate activities against different strains of bacteria and fungi tested.

scholarly journals The kinetics of the reduction of the lipophilic quinone avarone by N-alkyl-1,4-dihydronicotinamides of various lipophilicities

1999 ◽  
Vol 64 (11) ◽  
pp. 647-654 ◽  
Author(s):  
Mario Zlatovic ◽  
Dusan Sladic ◽  
Miroslav Gasic
Keyword(s):  
Cationic Surfactants ◽  
Reaction Rate ◽  
Anionic Surfactants ◽  
Reaction Rates ◽  
Biologically Active ◽  
Ionic Surfactants ◽  
Protic Solvent ◽  
Model Compounds ◽  
Kinetics Of ◽  
Long Chain

Several NADH model compounds, N-alkyl-1,4-dihydronicotinamides, some of them possessing amphiphilic properties, have been synthesized, and the kinetics of their reaction with a biologically active liphophilic quinone, avarone, has been studied in a protic solvent both in the presence and absence of cationic, anionic or non-ionic surfactants. In the absence of micellar agents, the medium- and long-chain N-dodecyl (3) and N-heptadecyl (4) derivatives show a significant increase in the reaction rates compared to other model compounds, due to the stabilization of the semiquinone intermediate. Anionic surfactants retard the reaction, non-ionic surfactants slightly accelerate the reaction with the short-chain derivatives, and retard the reaction with the medium- and long-chain derivatives, and the cationic surfactants increase the reaction rate with all derivatives except the long-chain 4. The results support the e-p-e mechanism of the reduction of lipophilic quinones byNADHmodels in protic medium.

scholarly journals Hydrogen bond simulation in molecular crystals of tyrosine

2019 ◽  
Vol 58 (6) ◽  
pp. 73-77
Author(s):  
Tatiana G. Volkova ◽  
◽  
Irina O. Talanova ◽  
Keyword(s):  
Amino Acids ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Interaction Energy ◽  
Biologically Active ◽  
Model Systems ◽  
Significant Difference ◽  
Molecular Associate ◽  
Order Of Magnitude ◽  
Chemical Simulation

The problem of the study of hydrogen bonds in biomolecules and living systems is important. Among the drugs, doctors emphasize substances of natural origin involved in metabolic processes. Such compounds include amino acids, peptides, vitamins, enzymes, macro- and microelements, and other biologically active substances, many of which are capable of forming hydrogen bonds. Amino acids and their derivatives are drugs of metabolic pharmacotherapy, characterized by low toxicity and severity of side effects. They also have virtually no allergenic effect, which makes them promising for the creation of drugs or their modifications. The instability of the hydrogen bond can significantly affect the state of pharmaceutical drug containing, for example, amino acids, during their storage, transportation or technological processing. One of the methods for studying the nature and determining the strength of hydrogen bonds is quantum chemical simulation. The calculation of the interaction energy in the studied molecular associate and its decomposition have been carried out according to Morocuma’s method (HF/6-31G (PC GAMESS). The evaluation of such energy components as electrostatic, exchange repulsion, polarization, charge transfer, mixing is given. The main contribution to the interaction energy comes from the electrostatic component. All the studied models have the same distribution of the components of the interaction energy in order of magnitude. Significant difference in the interaction energy in two model systems was noted, that could be explained by different geometry of hydrogen bonds. The comparison of received data made it possible to conclude that there are three types of hydrogen bonds in the molecular tyrosine crystal, which differ from each other in energy and geometry.

scholarly journals THE COMPONENT COMPOSITION OF THE PHYTOSTEROLS OF THE AERIAL PART OF THE HORSETAIL VAR-IEGATED ЕQUISÉTUM VARIEGATUM SCHLEICH. EX. WEB. GROWING IN NORTH-EAST YAKUTIA

2020 ◽  
pp. 133-148
Author(s):  
Lyubov' Vissarionovna Dudareva ◽  
Natal'ya Viktorovna Semenova ◽  
Vasiliy Vasil'yevich Nochsorov ◽  
Elena Georgievna Rudikovskaya ◽  
Klim Alekseyevich Petrov
Keyword(s):  
Aerial Part ◽  
Total Content ◽  
Dry Weight ◽  
Component Composition ◽  
Biologically Active ◽  
Farm Animals ◽  
Sterol Esters ◽  
Free Sterols ◽  
North East ◽  
Order Of Magnitude

It is known that phytosterols have high immunomodulating, hypocholesterolemic and oncoprotective activity and are widely used in medicine. In addition, the plants containing them are used in feed of farm animals as dietary supplements that stimulate growth and the immune system. Promising, but poorly studied, sources of these biologically active compounds may be plants of the class Horsetails (Equisetopsida), grown under extreme conditions of sharply continental climate of Yakutia. The steric composition of the aerial part of the variegated horsetail (Equisétum variegatum) was studied for the first time during the summer and autumn vegetation. It is shown that the composition of the main free sterols includes β-sitosterol, campesterol, stigmasterol, isofucosterol, as well as a small amount of cholesterol. The total amount of free and bound sterols in the tissues of the aerial part of this species is about 0.5 mg/g dry weight or 2% of the total content of all lipid components. Moreover, the content of free sterols in the aerial part of variegated horsetail is an order of magnitude higher than the content of sterol esters in these tissues. Peculiarities of the seasonal (autumn-summer) dynamics of changes in the relative contents of stigmasterol, campesterol and isofucosterol and the absolute total content of sterols in the aerial part of variegated horsetail are revealed.

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