Tetracyclic Nitrogen Research Articles

Synthesis and Theoretical Studies of Biologically Active Thieno Nucleus Incorporated Tri and Tetracyclic Nitrogen Containing Heterocyclics Scaffolds via Suzuki Cross-Coupling Reaction.

A new series of thieno nucleus embellished trinuclear (19, 20) and tetranuclear (21-24) nitrogen heteroaryl have been synthesized by the Suzuki cross-coupling reaction using bis(triphenylphosphine)palladium(II) dichloride. All the synthesized compounds were characterized by IR, 1 H-NMR, 13 CNMR and Mass spectral properties. In vitro antibacterial studies of the synthesized compound were conducted using broth microdilution assay employing Gram-positive and Gram-negative strains and half-maximal inhibitory concentration (IC50 ) was determined. The result showed that compound 20 possess best antibacterial activity against S. aureus and E. coli with IC50 values of 60 μg mL-1 and 90 μg mL-1 . Further to determine the mode of antibacterial action, compounds 20 and 21 were examined for in vitro bacterial dehydrogenase inhibitory assay. To understand the binding affinity of the synthesized compounds, the docking study was performed in the bacterial dehydrogenase enzyme by AutoDock Vina software and structure was confirmed by Discovery Studio Visualizer. All the synthesized compounds were docked in a good manner within the active sites of the bacterial dehydrogenase enzyme and exhibited good binding energies.

Iminyl radical-triggered relay annulation for the construction of bridged aza-tetracycles bearing four contiguous stereogenic centers.

Bridged tetracyclic nitrogen scaffolds are found in numerous biologically active molecules and medicinally relevant structures. Traditional methods usually require tedious reaction steps, and/or the use of structurally specific starting materials. We report an unprecedented, iminyl radical-triggered relay annulation from oxime-derived peresters and azadienes, which shows good substrate scope and functional group compatibility, and can deliver various bridged aza-tetracyclic compounds with complex molecular topology and four contiguous stereogenic centers (dr > 19 : 1) in a single operation. This transformation represents the first example of trifunctionalization of iminyl radicals through simultaneous formation of one C–N and two C–C bonds. DFT calculation studies were conducted to obtain an in-depth insight into the reaction pathways, which revealed that the reactions involved an interesting 1,6-hydrogen atom transfer process.

ChemInform Abstract: Silver‐Catalyzed Intramolecular C‐2 Selective Acylation of Indoles with Aldehydes: An Atom‐Economical Entry to Indole‐Indolone Scaffolds.

AbstractThe approach is possible under conditions A), B) or C) and affords various functionalized tetracyclic nitrogen skeletons, suitable as new drug‐like components.

Photochemistry of 1,4-Dihydropyridine Derivatives: Diradical Formation, Delocalization and Trapping as a Route to Novel Tricyclic and Tetracyclic Nitrogen Heterocyclic Ring Systems.

Irradiation of an acetonitrile solution of 4-aryl-3,5-dibenzoyl-1,4-dihydropyridine derivatives 1a–c and maleimides 2a–c using medium pressure Hg-arc lamp (λ > 290) nm afforded three different cycloadducts 4, 5, 6 in addition to the oxidation products 3. These results indicate that compounds 1a–c undergoes intermolecular cycloaddition reaction through three biradical intermediates and behave photochemically different than those reported previously for the analogous 3,5-diacetyl and 3,5-dicarboxylic acid derivatives. The present work also offers simple access to novel tricyclic and tetracyclic nitrogen heterocyclic ring systems of potential biological and synthetic applications. The structure of the photoproducts was established spectroscopically and by single crystal X-ray crystallography.

One-Step Synthetic Access to Isosteric and Potent Anticancer Nitrogen Heterocycles with the Benzo[c]phenanthridine Scaffold.

A versatile one-step two-component cyclization to build new tetracyclic nitrogen heterocycles is described. Ortho-methylhetarenecarbonitrile components were condensed with aldehydes to access a large library of differently substituted ring systems. The heterocyclic core can be easily modified by variation of the position of the endocyclic nitrogen atom in the o-methylhetarenecarbonitrile substrate. The manner of the nucleophilic attack that leads to the condensation can be triggered by different electron-density distribution in the molecule induced by the position of the nitrogen atom. Taking this into account, there is an electronic preference that leads to either pyridophenanthrolines or the corresponding pyridoazacarbazoles as the main products. We demonstrate the high antitumor potential of some of our synthesized heterocycles, which is strongly dependent on the substitution pattern introduced through the aldehyde component. The position and number of endocyclic nitrogen atoms play an important role regarding cytotoxicity of the studied compounds.

Neocryptolepine: A Promising Indoloisoquinoline Alkaloid with Interesting Biological Activity. Evaluation of the Drug and its Most Relevant Analogs.

Plants are one of the most important resources for the discovery of new drugs. The potential of natural compounds as new drug leads is clearly illustrated by the discovery and development of many modern medicines. This is an encouraging factor that drives natural products research in the vegetable kingdom. Neocryptolepine is a tetracyclic nitrogen heterocycle isolated from the African climber Cryptolepis sanguinolenta, which is widely used in traditional African medicine in many countries of Central and West Africa. The natural product is one of the representative examples of the small family of indolo[2,3-b]quinoline alkaloids, being endowed of multiple biological activities, including DNA-binding and inhibition of the enzyme topoisomerase II. It is also cytotoxic, antibacterial, antifungal and molluscicidal, also displaying antiprotozoal activity, particularly as antitrypanosomal, antileishmanial, antischistosomal and antiplasmodial. Some of these activities have been related to the product's ability to bind to DNA and to inhibit topoisomerase II; however, the exact mechanisms behind all of the observed bioactivities have not been comprehensively clarified. Major research activities regarding neocryptolepine have been focused into two seemingly opposite fields, related to its cytotoxic and antimalarial properties. Optimization of the natural product as a cytotoxic agent implied improvements in its bioavailability and activity, while the need of non-cytotoxic compounds guided the design and optimization of antimalarial agents. Therefore, the aim of the present article is to systematically review the current knowledge about the diversity of the biological activities related to neocryptolepine, its analogs and derivatives.

A New Way of Data Interpretation for Cognition Tests in Rats Used to Characterise Six Choline Esterase Inhibitors with Heterocyclic Nitrogen Bridgehead Structure

Six new tri- and tetracyclic nitrogen bridgehead compounds known to be moderate to potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in vitro were tested in vivo as experimental therapeutics for treatment of Alzheimer's disease. Cognitive impairment in rats was reversibly induced by scopolamine (CAS 51-34-3). The effect of the new substances was evaluated in an eight-arm radial maze and run times (1), errors (2), correct choices (3), correct choices per second (4), speed (5), and running distance (6) were recorded. For optimisation of data analysis a new strategy was used: A score was created on the basis of the 6 parameters described with score 1 for controls and score 4 for scopolamine rats. Scores above 4 indicate an impairment of cognition function compared to scopolamine. After equimolar dosage compared to the reference drug rivastigmine (CAS 123441-03-2), two of the new substances slightly improved cognition in rats, but only to a significantly lower degree compared to the irreversible inhibitor rivastigmine. Surprisingly, the other four compounds did not improve or even worsened the scopolamine effect on working memory.

Modern Friedel-Crafts chemistry. Part 32. Facile synthesis of some new fused heteropolycycles via direct intramoleclar Friedel-Crafts cyclialkylations of suitable heteroarylalkanols

This study provides expedient methods for the synthesis of some novel fused heteropolycycles. Thus, a variety of fused di-, tri- and tetracyclic nitrogen and nitrogen-sulfur heteropolycycles 8, 9, 11-15 were smoothly synthesized by Friedel-Crafts intramolecular alkylations of heteroarylalkanols 1-7 in the presence of both Bronsted (PPA and PTSA) and Lewis (AlCl3/CH3NO2) acid catalysts. The precursor alkanols were readily prepared by reaction of the corresponding carboxylic acid esters with methylmagnesium iodide. The structures of the compounds are established using both spectral and analytical data. A plausible carbocation mechanism is proposed to account for the results.

Formal Alder-ene reaction of a bicyclo[1.1.0]butane in the synthesis of the tricyclic quaternary ammonium core of daphniglaucins

A tricyclic substructure of the tetracyclic nitrogen core of the daphniglaucins was formed by an oxidative activation of the allyl side chain of a bicyclo[1.1.0]butylmethylamine, a spontaneous intramolecular formal Alder-ene reaction, and a selective cyclization of a triol intermediate.

P.5.b.006 The influence of apolipoprotein E epsilon4 allele on cognitive function in questionable dementia

Tetracyclic nitrogen bridgehead compounds, dibenzodiazecines and tricyclic quinazolinimines, in which the size of the alicyclic ring system and the length of the alkyl chain between the quinazolinimine moiety and a phenyl ring connected to the imine nitrogen atom were changed systematically, were synthesized and their ability to inhibit acetyl- and butyrylcholinesterase (AChE/BChE), respectively, was evaluated. Moderate and strong inhibitors of BChE—compared to galanthamine and rivastigmine—were identified, which show mixed affinities or are moderately or highly selective towards BChE, respectively.

Novel tricyclic quinazolinimines and related tetracyclic nitrogen bridgehead compounds as cholinesterase inhibitors with selectivity towards butyrylcholinesterase

Tetracyclic nitrogen bridgehead compounds, dibenzodiazecines and tricyclic quinazolinimines, in which the size of the alicyclic ring system and the length of the alkyl chain between the quinazolinimine moiety and a phenyl ring connected to the imine nitrogen atom were changed systematically, were synthesized and their ability to inhibit acetyl- and butyrylcholinesterase (AChE/BChE), respectively, was evaluated. Moderate and strong inhibitors of BChE—compared to galanthamine and rivastigmine—were identified, which show mixed affinities or are moderately or highly selective towards BChE, respectively.

Synthesis of fused rings at a pivotal nitrogen: tandem Heck reactions of N-vinyl-2-iodobenzamides

A short two-step synthesis of the tetracyclic nitrogen heterocycles 2 (isoindoloneindole, isoindoloneisoquinoline and isoindolone[3]benzazepine) is presented. Condensation of the corresponding o-bromoarylamine with acetaldehyde followed by acylation with o-iodobenzoyl chloride affords the key dihalo N-vinylbenzamides 1 , which are then cyclized by a tandem Heck reaction.

Cycloaddition reactions of aldimines of 1,5-ketoaldehydes. Applications in the synthesis of polycyclic nitrogen heterocycles

Aliphatic aldimines of a range of cyclic and acyclic 1,5-ketoaldehydes undergo metal catalysed regio- and stereo-specific imine → azomethine ylide → cycloaddition cascades. Acid catalysed cyclisations of the NH group of the pyrrolidine products onto the ketone functionality results in novel tri- and tetra-cyclic nitrogen heterocycles.

ChemInform Abstract: Photochemistry of the Phthalimide System. Part 40. Photoreaction of Phthalimides Possessing an ortho‐Methylphenyl Group in Their N‐Side Chain. Synthesis of Tetracyclic Nitrogen Heterocycles.

AbstractThe phthalimides (I) and (III) are synthesized from potassium phthalimide and benzyl halides or from phthalic anhydride and phenethylamines.

Photoreaction of Phthalimides Possessing an ortho-Methylphenyl Group in Their N-Side Chain. Synthesis of Tetracyclic Nitrogen Heterocycles

Synthese d'isoindolo [2,1-b] isoquinoleines et d'isoindolo [1,2-b] benzoazepines-3 par photocyclisation de N-[o-methyl benzyl- ou -phenethyl] phtalimides