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Journal articles on the topic 'Heterocycle'

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Author: Grafiati

Published: 4 June 2021

Last updated: 7 July 2024

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1

Andres, C. J., Derek J. Denhart, Milind S. Deshpande, and Kevin W. Gillman. "Recent Advances in the Solid Phase Synthesis of Drug Heterocyclic Small Molecules." Combinatorial Chemistry & High Throughput Screening 2, no. 4 (August 1999): 191–210. http://dx.doi.org/10.2174/1386207302666220204193145.

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Abstract: Because of their synthetic challenge, broad range of physical I chemical properties, and diverse biological activities, heterocycles continue to be of interest to both the academic and industrial chemist. This review covers recent advances in the solid phase synthesis of drug-like heterocyclic small molecules. Syntheses which form the heterocycle on the solid phase are emphasized; syntheses in which a preformed heterocycle is functionalized on the solid support have been omitted. The majority of references are from publication year 1999. This review should be of interest to anyone involved in, or contemplating the solid phase synthesis of small molecule drug-like heterocycles, especially for combinatorial chemistry applications.

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2

Winne, Johan, Jan Hullaert, Bram Denoo, Mien Christiaens, and Brenda Callebaut. "Heterocycles as Moderators of Allyl Cation Cycloaddition Reactivity." Synlett 28, no. 18 (July 27, 2017): 2345–52. http://dx.doi.org/10.1055/s-0036-1588511.

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For the rapid elaboration of polycarbocyclic scaffolds, prevalent in many important families of terpenoid natural products, allyl cations derived from simple heterocyclic alcohols can be used as versatile reaction partners in both (4+3) and (3+2) cycloaddition pathways. Our recent progress in this area is outlined, pointing towards the untapped potential of heterocycles to act as reagents in novel or known but challenging organic transformations.1 Heterocyclic Reagents2 Cycloadditions and Allyl Cations3 Furfuryl Cations in Cycloadditions4 Heterocycle-Substituted Cations in Cycloadditions5 Mechanistic Considerations6 Conclusions and Outlook

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3

Rusu, Aura, Ioana-Maria Moga, Livia Uncu, and Gabriel Hancu. "The Role of Five-Membered Heterocycles in the Molecular Structure of Antibacterial Drugs Used in Therapy." Pharmaceutics 15, no. 11 (October 29, 2023): 2554. http://dx.doi.org/10.3390/pharmaceutics15112554.

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Five-membered heterocycles are essential structural components in various antibacterial drugs; the physicochemical properties of a five-membered heterocycle can play a crucial role in determining the biological activity of an antibacterial drug. These properties can affect the drug’s activity spectrum, potency, and pharmacokinetic and toxicological properties. Using scientific databases, we identified and discussed the antibacterials used in therapy, containing five-membered heterocycles in their molecular structure. The identified five-membered heterocycles used in antibacterial design contain one to four heteroatoms (nitrogen, oxygen, and sulfur). Antibacterials containing five-membered heterocycles were discussed, highlighting the biological properties imprinted by the targeted heterocycle. In some antibacterials, heterocycles with five atoms are pharmacophores responsible for their specific antibacterial activity. As pharmacophores, these heterocycles help design new medicinal molecules, improving their potency and selectivity and comprehending the structure-activity relationship of antibiotics. Unfortunately, particular heterocycles can also affect the drug’s potential toxicity. The review extensively presents the most successful five-atom heterocycles used to design antibacterial essential medicines. Understanding and optimizing the intrinsic characteristics of a five-membered heterocycle can help the development of antibacterial drugs with improved activity, pharmacokinetic profile, and safety.

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4

Niedballa, Jonas, and Thomas J. J. Müller. "Heterocycles by Consecutive Multicomponent Syntheses via Catalytically Generated Alkynoyl Intermediates." Catalysts 12, no. 1 (January 13, 2022): 90. http://dx.doi.org/10.3390/catal12010090.

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Multicomponent processes are beneficial tools for the synthesis of heterocycles. As densely substituted bifunctional electrophiles, ynones are essential intermediates by applying cyclocondensations or cycloadditions in numerous heterocycle syntheses. The respective alkynoyl intermediates are generally accessible by palladium-, copper- and palladium/copper-catalyzed alkynylation. In turn, the mild reaction conditions allow for a fast and versatile entry to functional heterocycles in the sense of consecutive multicomponent processes. This review collates and presents recent advances in accessing thirteen heterocycle classes and their applications by virtue of catalytic alkynoyl generation in diversity-oriented multicomponent syntheses in a one-pot fashion.

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5

Cui, Hai-Lei. "Recent Advances in DMSO-Based Direct Synthesis of Heterocycles." Molecules 27, no. 23 (December 2, 2022): 8480. http://dx.doi.org/10.3390/molecules27238480.

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Besides serving as a low-toxicity, inexpensive and easily accessible solvent, dimethyl sulfoxide (DMSO) has also been extensively used as a versatile reagent for the synthesis of functionalized molecules. Dimethyl sulfoxide can not only be utilized as a carbon source, a sulfur source and an oxygen source, but also be employed as a crucial oxidant enabling various transformations. The past decade has witnessed a large number of impressive achievements on the direct synthesis of heterocycles as well as modifications of heterocyclic compounds by applying DMSO as a reagent. This review summarized the DMSO-based direct heterocycle constructions from 2012 to 2022.

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6

Llopart, Carme Cantos, Conchita Ferrer, and John A. Joule. "Lithiation of 1-arylimidazol-2(1H)-ones and 1-aryl-4,5-dihydroimidazol-2(1H)-ones." Canadian Journal of Chemistry 82, no. 11 (November 1, 2004): 1649–61. http://dx.doi.org/10.1139/v04-137.

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1-Arylimidazol-2(1H)-ones are shown to be readily lithiated, using 2 mol equiv. of n-butyllithium, on the benzene ring, ortho to the heterocycle. 1-Aryl-4,5-dihydroimidazol-2(1H)-ones also undergo metalation on the aromatic substitutuent ortho to the heterocycle, but less efficiently. 1-Aryl-3-methylimidazol-2(1H)-ones are lithiated on the heterocyclic ring and then on the benzene ring ortho to the heterocycle. No ortho-directing effect was found for 1-aryl-4,5-dihydro-3-methylimidazol-2(1H)-ones.Key words: ortho-lithation, ureas for directed ortho metalation, 1-arylimidazol-2-ones, 1-arylimidazolidin-2-ones.

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7

Xia, Xiao-Feng, and Yan-Ning Niu. "Recent developments in the synthesis of nitrogen-containing heterocycles from β-aminovinyl esters/ketones as CC–N donors." Organic & Biomolecular Chemistry 20, no. 2 (2022): 282–95. http://dx.doi.org/10.1039/d1ob01998h.

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8

Sparr, Christof, and Christian Fischer. "Configurationally Stable Atropisomeric Acridinium Fluorophores." Synlett 29, no. 16 (August 3, 2018): 2176–80. http://dx.doi.org/10.1055/s-0037-1610233.

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Arylated heterocyclic fluorophores are particularly useful scaffolds for numerous applications, such as bioimaging or synthetic photochemistry. While variation of the substitution pattern at the heterocycle and aryl groups allows dye modulation, the bond rotational barriers are also strongly affected. Unsymmetrically substituted ring systems of rotationally restricted arylated heterocycles therefore lead to configurationally stable atropisomeric fluorophores. Herein, we describe these characteristics by determining the properties and configurational stability of atropisomeric, tri-ortho-substituted naphthyl-acridinium fluorophores. A significant barrier to rotation of >120 kJ mol–1 was measured, which renders these dyes and related compounds distinct atropisomers with stereoisomer-specific properties over a broad temperature range.

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9

Prager, RH, Y. Singh, and B. Weber. "The Chemistry of 5-Oxodihydroisoxazoles. VIII. Photolysis of 2-(Heterocyclyl)isoxazol-5(2H)-ones." Australian Journal of Chemistry 47, no. 7 (1994): 1249. http://dx.doi.org/10.1071/ch9941249.

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Photolysis of 2-( heterocyclyl )isoxazol-5(2H)-ones occurs readily at 300 nm. In alcohol the products are the corresponding 2-alkoxy-3-heterocyclylaminoacrylates, and, in the presence of 1 M trifluoroacetic acid, the corresponding imidazole annulated heterocycle . Examples are reported where the heterocycle is quinolin-2-yl (10 examples), isoquinolin-1-yl, benzoxazol-2-yl, benzothiazol-2-yl, quinazolin-1-yl and pyrimidin-2-yl.

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10

Olyaei, Abolfazl, and Mahdieh Sadeghpour. "Chemistry of 3-cyanoacetyl indoles: synthesis, reactions and applications: a recent update." RSC Advances 13, no. 31 (2023): 21710–45. http://dx.doi.org/10.1039/d3ra04385a.

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11

Shoji, Taku, Tetsuo Okujima, and Shunji Ito. "Development of Heterocycle-Substituted and Fused Azulenes in the Last Decade (2010–2020)." International Journal of Molecular Sciences 21, no. 19 (September 25, 2020): 7087. http://dx.doi.org/10.3390/ijms21197087.

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Azulene derivatives with heterocyclic moieties in the molecule have been synthesized for applications in materials science by taking advantage of their unique properties. These derivatives have been prepared by various methods, involving electrophilic substitution, condensation, cyclization, and transition metal-catalyzed cross-coupling reactions. Herein, we present the development of the synthetic methods, reactivities, and physical properties for the heterocycle-substituted and heterocycle-fused azulenes reported in the last decade.

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12

Li, Xianwei, Tianzhang Wang, Yu-Jing Lu, Shaomin Ji, Yanping Huo, and Bifu Liu. "Copper-catalyzed oxidative multicomponent reaction: synthesis of imidazo fused heterocycles with molecular oxygen." Organic & Biomolecular Chemistry 16, no. 39 (2018): 7143–51. http://dx.doi.org/10.1039/c8ob01532e.

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An oxidative cascade that involves multicomponent reaction comprising a terminal alkyne, 2-amino N-heterocycle, benzyl or allylic bromide with molecular oxygen, delivering densely functionalized imidazo fused heterocycles, is achieved.

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13

Munzeiwa, Wisdom A., Bernard Omondi, and Vincent O. Nyamori. "Architecture and synthesis of P,N-heterocyclic phosphine ligands." Beilstein Journal of Organic Chemistry 16 (March 12, 2020): 362–83. http://dx.doi.org/10.3762/bjoc.16.35.

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Diverse P,N-phosphine ligands reported to date have performed exceptionally well as auxiliary ligands in organometallic catalysis. Phosphines bearing 2-pyridyl moieties prominently feature in literature as compared to phosphines with five-membered N-heterocycles. This discussion seeks to paint a broad picture and consolidate different synthetic protocols and techniques for N-heterocyclic phosphine motifs. The introduction provides an account of P,N-phosphine ligands, and their structural and coordination benefits from combining heteroatoms with different basicity in one ligand. The body discusses the synthetic protocols which focus on P–C, P–N-bond formation, substrate and nucleophile types and different N-heterocycle construction strategies. Selected references are given in relation to the applications of the ligands.

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14

Geisenberger, Josef, Jürgen Erbe, Jürgen Heidrich, Ulrich Nagela, and Wolfgang Beck. "Pseudohalogenometallverbindungen, LXV [1] Synthese von Tetrazolen und Triazolen über die 1,3-dipolare Cycloaddition an die Azid-Liganden von polymeren Cobalt(III)-und Palladium(II)-Komplexen. Darstellung und Struktur von 5-TrichlormethyItetrazol / Pseudohalogeno Metal Compounds, LXV [1] Synthesis of Tetrazoles and Triazoles via 1,3-Dipolar Cycloaddition to the Azido Ligands of Polymerie Cobalt(III) and Palladium(II) Complexes. Synthesis and Structure of 5-Trichloromethyltetrazole." Zeitschrift für Naturforschung B 42, no. 1 (January 1, 1987): 55–64. http://dx.doi.org/10.1515/znb-1987-0112.

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Abstract The cycloaddition of nitriles and of dimethylacetylenedicarboxylate to the azide ligand of polymeric Schiff Base cobalt(III) and phosphine palladium(II) complexes gives the corresponding tetrazolate and triazolate complexes from which the heterocycles could be cleaved by hydrogen chloride. Usually the yields are low; if the heterocycle is soluble in ether or sublimable, yields up to 30% have been obtained. Using this method the hitherto unknown 5-trichlormethyltetrazole could be prepared which was characterized by an X-ray structural analysis. Similarly, the cyclo-addition of azido(tetraphenylporphinato)cobalt(III) with nitriles, cyclohexylisocyanide and MeO2CC≡CCO2 Me affords the corresponding complexes with heterocyclic ligands. The prepa-ration of tetraphenylporphyrinato(tricyanmethanido)cobalt(III), (TPP)CoN=CC(CN)2 , is reported.

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15

Ala, Paul J., Lucie Gonneville, Milton C. Hillman, Mary Becker-Pasha, Min Wei, Brian G. Reid, Ronald Klabe, et al. "Structural Basis for Inhibition of Protein-tyrosine Phosphatase 1B by Isothiazolidinone Heterocyclic Phosphonate Mimetics." Journal of Biological Chemistry 281, no. 43 (August 17, 2006): 32784–95. http://dx.doi.org/10.1074/jbc.m606873200.

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Crystal structures of protein-tyrosine phosphatase 1B in complex with compounds bearing a novel isothiazolidinone (IZD) heterocyclic phosphonate mimetic reveal that the heterocycle is highly complementary to the catalytic pocket of the protein. The heterocycle participates in an extensive network of hydrogen bonds with the backbone of the phosphate-binding loop, Phe182 of the flap, and the side chain of Arg221. When substituted with a phenol, the small inhibitor induces the closed conformation of the protein and displaces all waters in the catalytic pocket. Saturated IZD-containing peptides are more potent inhibitors than unsaturated analogs because the IZD heterocycle and phenyl ring directly attached to it bind in a nearly orthogonal orientation with respect to each other, a conformation that is close to the energy minimum of the saturated IZD-phenyl moiety. These results explain why the heterocycle is a potent phosphonate mimetic and an ideal starting point for designing small nonpeptidic inhibitors.

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16

Yang, Ke, Zhi Li, Qingyue Hu, Mazen Elsaid, Chong Liu, Jun Chen, and Haibo Ge. "Recent Strategies in Nickel-Catalyzed C–H Bond Functionalization for Nitrogen-Containing Heterocycles." Catalysts 12, no. 10 (October 2, 2022): 1163. http://dx.doi.org/10.3390/catal12101163.

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N-heterocycles are ubiquitous in natural products, pharmaceuticals, organic materials, and numerous functional molecules. Among the current synthetic approaches, transition metal-catalyzed C–H functionalization has gained considerable attention in recent years due to its advantages of simplicity, high atomic economy, and the ready availability of starting materials. In the field of N-heterocycle synthesis via C–H functionalization, nickel has been recognized as one of the most important catalysts. In this review, we will introduce nickel-catalyzed intramolecular and intermolecular pathways for N-heterocycle synthesis from 2008 to 2021.

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17

Slivka, Mikhailo, and Mikhailo Onysko. "The Use of Electrophilic Cyclization for the Preparation of Condensed Heterocycles." Synthesis 53, no. 19 (May 19, 2021): 3497–512. http://dx.doi.org/10.1055/s-0040-1706036.

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AbstractCondensed heterocycles are well-known for their excellent biological effects and they are undeniably important compounds in organic chemistry. Electrophilic cyclization reactions are widely used for the synthesis of mono-heterocyclic compounds. This review highlights the utility of electrophilic cyclization reactions as an effective generic tool for the synthesis of various condensed heterocycles containing functional groups that are able to undergo further chemical transformations, such as nucleophilic substitution, elimination, re-cyclization, cleavage, etc. This review describes the reactions of unsaturated derivatives of different heterocycles with various electrophilic agents (halogens, arylsulfanyl chlorides, mineral acids) resulting in annulation of an additional partially saturated heterocycle. The electrophilic reaction conditions, plausible mechanisms and the use of such transformations in organic synthesis are also discussed. The review mainly focuses on research published since 2002 in order to establish the current state of the art in this area. 1 Introduction2 Electrophilic Cyclization Pathways Involving a Nitrogen Nucleophilic Center3 Electrophilic Cyclization Pathways Involving a Chalcogen Nucleophilic Center3.1 Sulfur Centers3.2 Oxygen Centers3.3 Selenium Centers4 Strategies and Mechanisms5 Conclusion

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18

Luna, Isadora Silva, Rayssa Marques Duarte da Cruz, Ryldene Marques Duarte da Cruz, Rodrigo Santos Aquino de Araújo, and Francisco Jaime Bezerra Mendonça-Junior. "1,4-Dithiane-2,5-diol: A Versatile Synthon for the Synthesis of Sulfur-containing Heterocycles." Current Organic Synthesis 15, no. 8 (December 17, 2018): 1026–42. http://dx.doi.org/10.2174/1570179415666180821154551.

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Background: 1,4-Dithiane-2,5-diol (1,4-DTD) is the stable dimer of α-mercapto acetaldehyde. This commercially available ambidentade compound is characterized as having in its chemical structure one group that acts as an electrophile and another that acts as a nucleophile, this permits its use as versatile and efficient synthon in synthetic heterocycle procedures. Objective: The aim of this review is to present synthetic applications of 1,4-DTD in heterocyclic chemistry and their applicability to the synthesis of bioactive compounds. Conclusion: Gewald reactions to obtain C-4 and C-5 unsubstituted 2-amino-thiophene derivatives; sulfa- Michael/Henry and sulfa-Michael/aldol sequences to obtain polysubstituted tetrahydrothiophenes, and other heterocyclic reactions that allow synthesizing several functionalized sulfur-containing heterocycles such as thiazolidines, oxathiazinoles and thiazoles are presented and discussed. The use of such heterocyclics in subsequent reactions allows obtaining various bioactive compounds including the antiretroviral lamivudine which is one of the examples presented in this review.

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19

Lizzadro, Luca, Oliver Spieß, Silke Reinecke, Marc Stadler, and Dieter Schinzer. "Synthesis of a Non-Symmetrical Disorazole C1-Analogue and Its Biological Activity." Molecules 29, no. 5 (March 1, 2024): 1123. http://dx.doi.org/10.3390/molecules29051123.

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The synthesis of a novel disorazole C1 analogue is described, and its biological activity as a cytotoxic compound is reported. Based on our convergent and flexible route to the disorazole core, we wish to report a robust strategy to synthesize a non-symmetrical disorazole in which we couple one half of the molecule containing the naturally occurring oxazole heterocycle and the second half of the disorazole macrocycle containing a thiazole heterocycle. This resulted in a very unusual non-symmetrical disorazole C1 analogue containing two different heterocycles, and its biological activity was studied. This provided exciting information about SAR (structure-activity-relationship) for this highly potent class of antitumor compounds.

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20

Deng, Yongming, Qing-Qing Cheng, and Michael Doyle. "Asymmetric [3+3] Cycloaddition for Heterocycle Synthesis." Synlett 28, no. 14 (July 5, 2017): 1695–706. http://dx.doi.org/10.1055/s-0036-1588453.

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Asymmetric syntheses of six-membered ring heterocycles are important research targets not only in synthetic organic chemistry but also in pharmaceuticals. The [3+3]-cycloaddition methodology is a complementary strategy to [4+2] cycloaddition for the synthesis of heterocyclic compounds. Recent progress in [3+3]-cycloaddition processes provide powerful asymmetric methodologies for the construction of six-membered ring heterocycles with one to three heteroatoms in the ring. In this account, synthetic efforts during the past five years toward the synthesis of enantioenriched six-membered ring heterocycles through asymmetric [3+3] cycloaddition are reported. Asymmetric organocatalysis uses chiral amines, thioureas, phosphoric acids, or NHC catalysis to achieve high enantiocontrol. Transition-metal catalysts used as chiral Lewis acids to activate a dipolar species is an alternative approach. The most recent advance, chiral transition-metal-catalyzed reactions of enoldiazo compounds, has contributed toward the versatile and highly selective synthesis of six-membered heterocyclic compounds.1 Introduction2 Asymmetric Formal [3+3]-Cycloaddition Reactions by Organocatalysis2.1 By Amino-Catalysis2.2 By N-Heterocyclic Carbenes2.3 By Bifunctional Tertiary Amine-thioureas2.4 By Chiral Phosphoric Acids3 Asymmetric Formal [3+3]-Cycloaddition Reactions by Transition-Metal Catalysis3.1 Copper Catalysis3.2 Other Transition-Metal Catalysis4 Asymmetric [3+3]-Cycloaddition Reactions of Enoldiazo Compounds4.1 Asymmetric [3+3]-Cycloaddition Reactions of Nitrones with Electrophilic Metallo-enolcarbene Intermediates4.2 Dearomatization in Asymmetric [3+3]-Cycloaddition Reactions of Enoldiazoacetates4.3 Asymmetric Stepwise [3+3]-Cycloaddition Reaction of Enoldiazoacetates with Hydrazones5 Summary and Outlook

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21

Zhang, Zhen-Zhen, Yongna Zhang, Hui-Xin Duan, Zhuo-Fei Deng, and You-Qing Wang. "Enantioselective (3+2) cycloaddition via N-heterocyclic carbene-catalyzed addition of homoenolates to cyclic N-sulfonyl trifluoromethylated ketimines: synthesis of fused N-heterocycle γ-lactams." Chemical Communications 56, no. 10 (2020): 1553–56. http://dx.doi.org/10.1039/c9cc09269b.

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An enantioselective (3+2) cycloaddition via N-heterocyclic carbene-catalyzed homoenolate addition to cyclic N-sulfonyl trifluoromethyl ketimines is realized, affording fused N-heterocycle γ-lactams with up to >20 : 1 dr and 94–99% ee.

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22

Gorbulenko, Natalia, Tetyana Shokol, and Volodymyr Khilya. "Isoflavonoids Modified with Azole Heterocycles with Three Heteroatoms." French-Ukrainian Journal of Chemistry 10, no. 1 (2022): 101–27. http://dx.doi.org/10.17721/fujcv10i1p101-127.

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Heterocycle modified chromones are attracting increasing attention as novel potential therapeutic agents due to their effective bioactivities and low toxicity. This review describes all strategies and versatile synthons that have been developed for the synthesis of isoflavone heterocyclic analogs containing isolated 5-member heterocyclic rings with three identical or different heteroatoms. Their biological activity is also presented.

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23

Panchal, Neil B., and Vipul M. Vaghela. "Pteridine a Colored Heterocycle and its Anticancer Activity: An Overview." Oriental Journal Of Chemistry 38, no. 4 (August 31, 2022): 822–39. http://dx.doi.org/10.13005/ojc/380402.

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The objective of this work is to provide an overview of the numerous pharmacological features that are associated with the pteridine molecule. Pteridines are nitrogen-containing heterocyclic compounds that are well-known and noteworthy. Their chemical formula is C6H4N4.In recent years, pteridine's various potential uses in the field of medicinal chemistry research have garnered significant attention. In the expanding field of intensive study, Pteridine is regarded as a privileged scaffold, and the alteration created with diverse substituents around the centroid opened the way for researchers to deal with it at ease. The heterocycle, which is a fused ring, has a high pharmacological quality. A pteridine is one of the heterocycles that has attracted a lot of interest in terms of biological uses. The pteridine nucleus serves as the quintessential framework in a range of physiologically energetic chemicals and pharmacological molecules. This evaluation is necessary in order to bring to light the remarkable potential that this ring device possesses as a result of the wide variety of pharmacological effects it may perform. This research might unquestionably hasten the graph and synthesis procedures, which would ultimately yield in a wide array of therapeutically feasible medicinal options.

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24

Niu, Jingze, and Michael C. Willis. "Heterocycle-derived β-S-enals as bifunctional linchpins for the catalytic synthesis of saturated heterocycles." Organic Chemistry Frontiers 3, no. 5 (2016): 625–29. http://dx.doi.org/10.1039/c6qo00057f.

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We demonstrate how heterocycle-derived β-S-enals can be employed as bifunctional substrates in a cascade of two rhodium-catalysed C–C bond forming reactions – a hydroacylation followed by a Suzuki-type coupling – to deliver substituted heterocyclic products.

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25

Maciejewski, Andrzej, Anna Jaworska-Augustyniak, Dariusz Radocki, Ronald G. Sutherland, and Adam Piórko. "An efficient photochemical formation of phenoxazine and phenothiazine from their respective cyclopentadienyliron complexes." Collection of Czechoslovak Chemical Communications 54, no. 8 (1989): 2171–75. http://dx.doi.org/10.1135/cccc19892171.

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The photochemical liberation of phenoxazine and phenothiazine from their cyclopentadienyliron complexes was studied in THF, methanol and dimethylsulfoxide. Quantum yields of decay of the complexes and the formation of free heterocycles have been determined to be about 1.0, independent of solvent, concentration and wavelength of light used. The ease of isolation of free heterocycles after photolysis show that this efficient way of heterocycle recovery is superior to the previously utilized pyrolytic sublimation.

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26

Chmovzh, Timofey N., Daria A. Alekhina, Timofey A. Kudryashev, and Oleg A. Rakitin. "Efficient Synthesis of 4,8-Dibromo Derivative of Strong Electron-Deficient Benzo[1,2-d:4,5-d’]bis([1,2,3]thiadiazole) and Its SNAr and Cross-Coupling Reactions." Molecules 27, no. 21 (October 30, 2022): 7372. http://dx.doi.org/10.3390/molecules27217372.

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An efficient synthesis of hydrolytically and thermally stable 4,8-dibromobenzo[1,2-d:4,5-d’]bis([1,2,3]thiadiazole) by the bromination of its parent heterocycle is reported. The structure of 4,8-dibromobenzo[1,2-d:4,5-d’]bis([1,2,3]thiadiazole) was confirmed by X-ray analysis. The conditions for the selective aromatic nucleophilic substitution of one bromine atom in this heterocyclic system by nitrogen nucleophiles are found, whereas thiols formed the bis-derivatives only. Suzuki–Miyaura cross-coupling reactions were found to be an effective method for the selective formation of various mono- and di(het)arylated derivatives of strong electron-deficient benzo[1,2-d:4,5-d’]bis([1,2,3]thiadiazole), and Stille coupling can be employed for the preparation of bis-arylated heterocycles, which can be considered as useful building blocks for the synthesis of DSSCs and OLEDs components.

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27

Olšovská, Jana, Karel Štěrba, Martin Slabý, and Tomáš Vrzal. "Novel method for determination of heterocyclic compounds and their impact in brewing technology." KVASNY PRUMYSL 67, no. 2 (April 15, 2021): 417–27. http://dx.doi.org/10.18832/kp2021.67.417.

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A new simultaneous method for determination of 16 heterocyclic compounds using SPE sample preparation and GC-MS determination was developed regarding increasing interest of the role of sensory active compounds in beer. LiChrolut® EN SPE columns proved to be optimal for both, a mixture of analytes with a different polarity and such complicated matrix as beer. Recoveries of individual analytes are about 100% except for three compounds (2-methylpyridine about 30%, maltol and furaneol about 50%); repeatability, uncertainty and LOQ are satisfactory for the method application. The method was used for monitoring of heterocyclic compounds formation during roasting, mashing, hop boiling and fermentation. To summarize, during roasting of malt, the concentration of oxygen heterocycle compounds (OHC) increases more rapidly in comparison with nitrogen heterocycles compounds (NHC) till a critical point where OHC starts to decrease and NHC starts to be formed sharper (with the exception of 2-acetylpyrrole which is similar to OHC). Finally, the total concentration of NHC during fermentation rapidly decreases whilst the OHC concentration is influenced by many factors, e.g., fermentation conditions and yeast strain.

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28

van Maarseveen, Jan H. "Solid Phase Synthesis of Heterocycles by Cyclization/Cleavage Methodologiest." Combinatorial Chemistry & High Throughput Screening 1, no. 4 (December 1997): 185–214. http://dx.doi.org/10.2174/1386207301666220125213031.

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For the solid phase preparation of various (pharmacologically important) heterocycles, cyclization/cleavage (C/C) or cyclorelease strategies proved to be superior. CC approaches take utmost advantage of the benefits of sol)d phase synthesis. Besides the practical benefits of solid phase reactions, cyclative release approaches are distinguished especially because of the generally found high purity of the final detached products, since only the anticipated structures cleave off the resin. Also cyclization/cleavage strategies are "traceless", as the obtained moiety after cyclization is part of the formed heterocycle. Over the last thirty years numerous approaches towards important heterocycle classes have been published. Among the successfully applied strategies are carbon-nitrogen (sulfur) bond, carbon-oxygen bond, sulfur-sulfur bond and carbon-carbon forming reactions in the final cyclorelease step.

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29

Boelke, Andreas, Soleicha Sadat, Enno Lork, and Boris J. Nachtsheim. "Pseudocyclic bis-N-heterocycle-stabilized iodanes – synthesis, characterization and applications." Chemical Communications 57, no. 60 (2021): 7434–37. http://dx.doi.org/10.1039/d1cc03097c.

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30

Prager, RH, TK Rosenzweig, and Y. Singh. "The Chemistry of 5-Oxodihydroisoxazoles. III. Synthesis of Further Annelated Pyrimidines." Australian Journal of Chemistry 45, no. 11 (1992): 1825. http://dx.doi.org/10.1071/ch9921825.

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The synthesis of some 2-heterocyclyl-5-oxo-2,5-dihydroisoxazole-4-carboxylates is reported, where the heterocycle is pyridin-2-yl, triazin-2-yl, pyrimidin-4-yl, quinolin-2-yl or phthalazin- 1-yl, as is their base-catalysed rearrangement to the corresponding annelated pyrimidines.

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31

Lynch, Daniel E., and Glyn D. Jones. "Geometry of the 2-aminoheterocyclic–carboxylic acid R 2 2(8) graph set: implications for crystal engineering." Acta Crystallographica Section B Structural Science 60, no. 6 (November 11, 2004): 748–54. http://dx.doi.org/10.1107/s0108768104023791.

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The geometry of the R_2^2(8) graph set formed between a 2-aminoheterocyclic ring containing an Nsp 2 atom (in the 1-position of the ring) and a carboxylic acid has been studied. Collating data from known co-crystal structures containing five- and six-membered heterocyclic rings from the Cambridge Structural Database revealed unexpected differences between two kinds of non-hydrogen contact distances, and between specific bond distances and angles of the heterocycle. Not only were the interatomic non-hydrogen distances between the N atoms (heterocycle) and O atoms (carboxylate) asymmetric, but also the 2-amino N atom (N21) to the heterocyclic C atom (C2) bond was shorter than the C2 to N1sp 2 bond. However, this shortening of the C2—N21 bond was not observed in the examples where N21 was substituted with a non-H atom. For the six-membered rings the data also showed that as the C2—N21 bond shortened the N1—C2—N21 bond angle increased.

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32

Naito, Takeaki. "Heterocycle synthesis via radical reactions." Pure and Applied Chemistry 80, no. 4 (January 1, 2008): 717–26. http://dx.doi.org/10.1351/pac200880040717.

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A novel synthetic method for the preparation of nitrogen-containing heterocycles via the route involving domino-type radical addition/cyclization reaction of oxime ethers is described. Alkyl radical addition/cyclization of oxime ethers carrying an appropriate leaving group proceeded smoothly to form the alkylated nitrogen-containing heterocyclic compounds. Additionally, tin-mediated radical addition/cyclization/elimination (RACE) reaction of oxime ethers is newly found and successfully applied to an asymmetric total synthesis of (-)-martinellic acid.

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Birzan, Liviu, Mihaela Cristea, Constantin C. Draghici, and Alexandru C. Razus. "Some Considerations Regarding the 1H and 13C Spectra of 4-(1-azulenyl)-2,6-bis(2-heteroaryl-vinyl)- pyrylium and Pyridinium and their Corresponding Pyridines." Revista de Chimie 69, no. 1 (February 15, 2018): 64–69. http://dx.doi.org/10.37358/rc.18.1.6045.

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The 1H and 13C NMR spectra of several 2,6-diheteroarylvinyl heterocycles containing 4-azulenyl moiety were recorded and their proton and carbon chemical shifts were compared with those of the compounds without double bond between the heterocycles. The influence of the nature of central and side heterocycles, molecule polarization and anisotropic effects were revealed. The highest chemical shifts were recorded for the pyrylium salts and the lowest at pyridines, but in the case of the pyridinium salts, the protons chemical shifts at the central heterocycle are more shielded due to a peculiar anisotropy of the attached vinyl groups.

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Ruiz, S., C. Carrera, P. Villuendas, and E. P. Urriolabeitia. "Ru-Catalysed synthesis of fused heterocycle-pyridinones and -pyrones." Organic & Biomolecular Chemistry 15, no. 42 (2017): 8904–13. http://dx.doi.org/10.1039/c7ob01497j.

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Heterocycle-pyridinones and heterocycle-pyranones have been prepared by Ru-catalysed oxidative coupling of N-unprotected primary heterocycle-amides and heterocycle-carboxylic acids with internal alkynes.

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35

Winand, Lea, Stefanie Theisen, Stephan Lütz, Katrin Rosenthal, and Markus Nett. "Immobilization of the Amidohydrolase MxcM and Its Application for Biocatalytic Flow Synthesis of Pseudochelin A." Catalysts 13, no. 2 (January 18, 2023): 229. http://dx.doi.org/10.3390/catal13020229.

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The chemical synthesis of heterocycles typically requires elevated temperature and acid or base addition to form the desired product. Moreover, these reactions often involve hazardous reagents, which is why biocatalytic routes for heterocycle formation have gained increasing attention. In recent years, several enzymes belonging to the amidohydrolase superfamily have been identified to generate heterocycles via cyclocondensation reactions. Of particular interest is the amidohydrolase MxcM, which catalyzes the formation of an imidazoline moiety in the biosynthesis of the anti-inflammatory natural product pseudochelin A. In this study, we present a concept for the immobilization of this enzyme using a fused hexahistidine tag for fixation onto a solid, porous carrier. Notably, the immobilization improves the enzyme’s tolerance to organic solvents. The immobilized MxcM exhibits a residual activity of 169% in the polar solvent acetonitrile compared to the free enzyme, and the storage stability in the presence of 20 vol% acetonitrile was ameliorated. In addition, an immobilized enzyme reactor (IMER) was designed that can be operated under flow conditions. The MxcM-IMER retains its biocatalytic activity and mechanic stability over the tested operation time. These results provide important insights for the integration of heterocycle-forming amidohydrolases in chemical processes.

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Shekarkhand, Marzieh, Karim Zare, Majid Monajjemi, Elham Tazikeh-Lemeski, and Masoumeh Sayadian. "Computational study of heterocyclic anticancer compounds through nbo method." Nexo Revista Científica 35, no. 01 (April 6, 2022): 367–81. http://dx.doi.org/10.5377/nexo.v35i01.13982.

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In the present study NBO method contain the HOMO and the LUMO energies are calculated for 10 different heterocycles anticancer drug using B3LYP/6-31G(d,p). Frontier molecular orbitals (HOMO and LUMO) and Molecular Electrostatic Potential map of the compound was produced by using the π stacking of structures and anticancer activity of molecules. The NBO analysis was suggested that the molecular system contains π- π interaction, strong conjugative interactions and the molecule become more polarized owing to the movement of π-electron cloud from donor to acceptor. NBO, HOMO and LUMO energies, were investigated and Anticancer activity of Aromatic Heterocyclic compounds was investigated by NBO study and result was compared with our previous study about NICS and S-NICS of these 10 anticancer drug. the HOMO/LUMO gap of the heterocycle anticancer drug is significantly different from each other. The NBO method is used in both symmetric and asymmetric molecules and provides accurate information on the aromatics of the compound, especially the heterocyclic rings. It also provides accurate information in protected areas. Molecule 8 has the highest amount of HOMO and therefore aromaticity among the studied compounds which confirms the result of molecular orbital examination.

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Palaniappan, Saravana Priya. "Pharmacological Role of Heterocyclic Compounds in the Treatment of Alzheimer’s Disease: A Review." Journal of Phytopharmacology 11, no. 4 (August 15, 2022): 289–94. http://dx.doi.org/10.31254/phyto.2022.11412.

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Alzheimer’s disease (AD) is a multifactorial neurological disease that mainly affects the old age people. Neuropathologically, AD is characterized by low level of acetylcholine, loss of synapses and neurons in certain brain regions, accumulation of extracellular amyloid beta peptide (Aβ) and phosphorylation of intracellular tau protein. Patients with AD are characterized by various symptoms such as memory deficits, depression, cognitive dysfunction and difficult to perform daily activities. Currently available drugs for the treatment of AD are used to treat symptomatic relief at an early stage, however the prolonged usage of the drugs may cause adverse side effects. To overcome this, development of drugs produced from natural products is considered as one of the promising alternatives for the treatment of AD. Among that heterocyclic compound play a major role in the development of therapeutic drugs against various disorders. An organic compound which is cyclic or non-cyclic consists of one or more atoms in their ring structure are known as heterocyclic compounds. These heterocyclic compounds occur both in natural and synthetic form and play a major role in the metabolism of all living cells. Most of the organic compounds used as drugs have a heterocyclic core in their skeleton. Nitrogenous bases such as purines and pyrimidines present in DNA, chlorophyll, vitamins contain heterocycle in their structure. Other compounds containing heterocycles are proline, morphine, furan, vinblastine, cephalosporin, penicillin etc. This review summarizes the nomenclature, classification, and the role of heterocyclic compounds in the treatment of Alzheimer's disease.

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Marzi, Mahrokh, Mojtaba Farjam, Zahra Kazeminejad, Abolfazl Shiroudi, Amin Kouhpayeh, and Elham Zarenezhad. "A Recent Overview of 1,2,3-Triazole-Containing Hybrids as Novel Antifungal Agents: Focusing on Synthesis, Mechanism of Action, and Structure-Activity Relationship (SAR)." Journal of Chemistry 2022 (January 6, 2022): 1–50. http://dx.doi.org/10.1155/2022/7884316.

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A pharmacophore system has been found as 1,2,3-triazole, a five-membered heterocycle ring with nitrogen heteroatoms. These heterocyclic compounds can be produced using azide-alkyne cycloaddition processes catalyzed by ruthenium or copper. The bioactive compounds demonstrated antitubercular, antibacterial, anti-inflammatory, anticancer, antioxidant, antiviral, and antidiabetic properties. This heterocycle molecule, in particular, with one or more 1,2,3-triazole cores has been found to have the most powerful antifungal effects. The goal of this review is to highlight recent developments in the synthesis and structure-activity relationship (SAR) investigation of this prospective fungicidal chemical. Also there have been explained drugs and mechanism of action of a triazole compound with antifungal activity. This review will be useful in a variety of fields, including medicinal chemistry, organic chemistry, mycology, and pharmacology.

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39

Martinez, Ana, Carmen Gil, Ana Castro, Ana M. Bruno, Concepción Pérez, Columbiana Prieto, and Joaquin Otero. "Benzothiadiazine Dioxide Human Cytomegalovirus Inhibitors: Synthesis and Antiviral Evaluation of Main Heterocycle Modified Derivatives." Antiviral Chemistry and Chemotherapy 14, no. 2 (April 2003): 107–14. http://dx.doi.org/10.1177/095632020301400206.

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The benzothiadiazine dioxide derivatives are potent non-nucleoside human cytomegalovirus (HCMV) inhibitors. As part of our comprehensive structure-activity relationship (SAR) study of these compounds, we have now proposed structural modifications on the heterocyclic moiety both on the number and the nature of the fused heterocycle and on the kind of heteroatoms pre-sent on it. Synthesis of these new compounds (benzyl derivatives of thiadiazines, thienothiadiazines, benzothienothiadiazines and quinazolines) and the antiviral evaluation against HCMV has been performed. SAR investigation on this class of compounds has defined the structural requirements for potency and toxicity. They have revealed two important clues: i) a fused ring to the thiadiazine framework is necessary to maintain the anti-HCMV action, and ii) the sulfamido moiety in the main heterocycle is crucial to avoid cytotoxicity.

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40

Wang, Kai-Min, Sheng-Jiao Yan, and Jun Lin. "Heterocyclic Ketene Aminals: Scaffolds for Heterocycle Molecular Diversity." European Journal of Organic Chemistry 2014, no. 6 (November 20, 2013): 1129–45. http://dx.doi.org/10.1002/ejoc.201300929.

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41

Feng, Li, Xiaolei Ren, Yangyang Feng, Bochuan Tan, Shengtao Zhang, Wenpo Li, and Jie Liu. "Self-assembly of new O- and S-heterocycle-based protective layers for copper in acid solution." Physical Chemistry Chemical Physics 22, no. 8 (2020): 4592–601. http://dx.doi.org/10.1039/c9cp06910k.

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Two heterocycle-based indole self-assembly monolayers (SAMs) including O-heterocycle indole (FYBI) and S-heterocycle indole (TYBI) have been synthesized and investigated on copper corrosion inhibition.

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42

Adlu, Maryam, and Issa Yavari. "One-pot, mild and efficient multicomponent synthesis of novel various spiro-nitrogen heterocycle compounds." Bulletin of the Chemical Society of Ethiopia 37, no. 1 (October 26, 2022): 115–22. http://dx.doi.org/10.4314/bcse.v37i1.10.

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ABSTRACT. One-pot, mild and efficient synthesis of various spiro-nitrogen heterocycle compounds, based on the reaction of ninhydrin and 1,2-diamino-benzene, (indenoquinoxalin), with N-heterocycle compounds and dialkylacetylenedicarboxylates is described. Using this approach, various spiro-nitrogen heterocycle compounds at a temperature of 50-60 °C in acetonitrile solvent, can be obtained very high yields. KEY WORDS: Ninhydrin, 1,2-Diaminobenzene, spiro-Nitrogen heterocycle compounds, Indenoquinoxalin, N-heterocycle compounds, Dialkylacetylenedicarboxylates Bull. Chem. Soc. Ethiop. 2023, 37(1), 115-122. DOI:https://dx.doi.org/10.4314/bcse.v37i1.10

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43

de Ceuninck van Capelle, Lillian A., James M. Macdonald, and Christopher J. T. Hyland. "Stereogenic and conformational properties of medium-ring benzo-fused N-heterocycle atropisomers." Organic & Biomolecular Chemistry 19, no. 33 (2021): 7098–115. http://dx.doi.org/10.1039/d1ob00836f.

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By examining the various contributions to the conformational and stereogenic stability of medium-sized benzo-fused N-heterocyclic atropisomers, this review serves to aid the design, synthesis and study of these pharmaceutically relevant heterocycles.

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44

Fernandes, Sara, João Aires-de-Sousa, Michael Belsley, and M. Raposo. "Synthesis of Pyridazine Derivatives by Suzuki-Miyaura Cross-Coupling Reaction and Evaluation of Their Optical and Electronic Properties through Experimental and Theoretical Studies." Molecules 23, no. 11 (November 18, 2018): 3014. http://dx.doi.org/10.3390/molecules23113014.

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A series of π-conjugated molecules, based on pyridazine and thiophene heterocycles 3a–e, were synthesized using commercially, or readily available, coupling components, through a palladium catalyzed Suzuki-Miyaura cross-coupling reaction. The electron-deficient pyridazine heterocycle was functionalized by a thiophene electron-rich heterocycle at position six, and different (hetero)aromatic moieties (phenyl, thienyl, furanyl) were functionalized with electron acceptor groups at position three. Density Functional Theory (DFT) calculations were carried out to obtain information on the conformation, electronic structure, electron distribution, dipolar moment, and molecular nonlinear response of the synthesized push-pull pyridazine derivatives. Hyper-Rayleigh scattering in 1,4-dioxane solutions, using a fundamental wavelength of 1064 nm, was used to evaluate their second-order nonlinear optical properties. The thienylpyridazine functionalized with the cyano-phenyl moiety exhibited the largest first hyperpolarizability (β = 175 × 10−30 esu, using the T convention) indicating its potential as a second harmonic generation (SHG) chromophore.

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45

Asif, Mohammad. "Biological Potential and Chemical Properties of Pyridine and Piperidine Fused Pyridazine Compounds: Pyridopyridazine a Versatile Nucleus." Asian Journal of Chemistry and Pharmaceutical Sciences 1, no. 1 (November 21, 2016): 29. http://dx.doi.org/10.18311/ajcps/2016/7693.

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Pyridopyridazine compounds are important nitrogen atom containing heterocyclic compounds due to their pharmacological versatility. This heterocycle system characterized a structural feature for different types of bioactive compounds that exhibiting various types of biological activities which make it an attractive scaffold for the design and development of new drug molecules. This article provided information about the pharmacological properties of pyridopyridazines derivatives.

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46

Nehra, Bhupender, Bijo Mathew, and Pooja A. Chawla. "A Medicinal Chemist’s Perspective Towards Structure Activity Relationship of Heterocycle Based Anticancer Agents." Current Topics in Medicinal Chemistry 22, no. 6 (March 2022): 493–528. http://dx.doi.org/10.2174/1568026622666220111142617.

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Aim: This paper aims to describe the structure activity relationship of heterocyclic deriva-tives with multi-targeted anticancer activity. Objectives: With the following goals in mind, this review tries to describe significant recent advances in the medicinal chemistry of heterocycle-based compounds: (1) To shed light on recent literature focused on heterocyclic derivatives' anticancer potential; (2) To discuss recent advances in the medic-inal chemistry of heterocyclic derivatives, as well as their biological implications for cancer eradica-tion; (3) To summarise the comprehensive correlation of structure activity relationship (SAR) with pharmacological outcomes in cancer therapy. Background: Cancer remains one of the major serious health issues in the world today. Cancer is a complex disease in which improperly altered cells proliferate at an uncontrolled, rapid, and severe rate. Variables such as poor dietary habits, high stress, age, and smoking, can all contribute to the development of cancer. Cancer can affect almost any organ or tissue, although the brain, breast, liver, and colon are the most frequently affected organs. For several years, surgical operations and irradia-tion have been in use along with chemotherapy as a primary treatment of cancer, but still, effective treatment of cancer remains a huge challenge. Chemotherapy is now considered one of the most ef-fective strategies to eradicate cancer, although it has been shown to have a number of cytotoxic and unfavourable effects on normal cells. Despite all of these cancer treatments, there are several other targets for anticancer drugs. Cancer can be effectively eradicated by focusing on these targets, includ-ing cell-specific and receptor-specific targets such as tyrosine kinase receptors (TKIs). Heterocyclic scaffolds also have a variety of applications in drug development and are a common moiety in the pharmaceutical, agrochemical, and textile industries. Methods: The association between structural activity relationship data of many powerful compounds and their anticancer potential in vitro and in vivo has been studied. SAR of powerful heterocyclic compounds can also be generated using molecular docking simulations, as reported in literature. Conclusions: Heterocycles have a wide range of applications, from natural compounds to synthesised derivatives with powerful anticancer properties. To avoid cytotoxicity or unfavourable effects on normal mammalian cells due to a lack of selectivity towards the target site, as well as to reduce the occurrence of drug resistance, safer anticancer lead compounds with higher potency and lower cyto-toxicity are needed. This review emphasizes on design and development of heterocyclic lead com-pounds with promising anticancer potential.

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47

Moulis, Pierre, Cécile Miot-Sertier, Laure Cordazzo, Olivier Claisse, Céline Franc, Laurent Riquier, Warren Albertin, et al. "Which microorganisms contribute to mousy off-flavour in our wines?" OENO One 57, no. 2 (May 16, 2023): 177–87. http://dx.doi.org/10.20870/oeno-one.2023.57.2.7481.

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In recent years, the frequency of occurrence of mousy off-flavours in wines has increased. This could be caused by the significant decrease in sulphur dioxide addition during processing, the increase in pH or even the trend for spontaneous fermentation in wine. This off-flavour was associated with Brettanomyces bruxellensis or lactic acid bacteria metabolisms. Three N-heterocyclic compounds (APY, ETHP, ATHP) were described as involved in mousiness perception. Thus far, no study addressed the variability in that N-heterocycles production according to microorganism strains from different species. Twenty-five wines presenting mousy off-flavour were analysed. In total, 252 bacteria with 90.5 % of Oenococcus oeni and 101 yeast strains with 53.5 % of Saccharomyces cerevisiae were isolated and identified. Their capacity to produce mousy compounds was investigated using Stir Bar Sorptive Extraction-Gas Chromatography-Mass Spectrometry (SBSE-GC-MS) and a standardised N-heterocycle assay medium. While four and three species of yeast and bacteria, respectively, were isolated from mousy wines, only three species of microorganisms were associated with N-heterocycles production: B. bruxellensis, Lentilactobacillus hilgardii and Oenococcus oeni. The screening was then extended to collection strains for these three species to improve their genetic representativity. Our results show that the levels and the ratios of the three N-heterocycles present huge variations according to the species. In addition, it has been shown that in most mousy wines, B. bruxellensis was not found. Finally, an interesting correlation between ATHP and ETHP was identified.

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Iqbal, S. A., K. Yuan, J. Cid, J. Pahl, and M. J. Ingleson. "Controlling selectivity in N-heterocycle directed borylation of indoles." Organic & Biomolecular Chemistry 19, no. 13 (2021): 2949–58. http://dx.doi.org/10.1039/d1ob00018g.

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N-Heterocycle directing groups lead to selective borylation of indole at C2 or C7 controlled by heterocycle ring size. With five membered heterocycle directing groups, C2 borylation is disfavoured due to an increased degree of distortion.

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49

Breitwieser, Kevin, and Peter Chen. "Crystal structure of a 1,1-dibutyl-1H,3H-naphtho[1,8-cd][1,2,6]oxastannaborinin-3-ol." Acta Crystallographica Section E Crystallographic Communications 77, no. 2 (January 26, 2021): 180–83. http://dx.doi.org/10.1107/s2056989021000712.

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The title oxastannaborininol compound, [Sn(C4H9)2(C10H7BO2)], has been synthesized and crystallized. While heterocycles containing a C–O–B group are common, heterocycles containing an E–O–B unit, where E is an element of the carbon group except for carbon, are rare. In fact, while heterocycles containing Si–O–B units are occasionally reported (although without crystal structures), there are no reports for the corresponding germanium, tin or lead analogues. Herein, the first synthesis and crystal structure of a heterocycle containing an Sn–O–B unit is described. The asymmetric unit contains one molecule showing a notable disorder of the tin atom and the butyl groups. They occupy two sets of positions with site-occupancy factors of 0.295 (6) and 0.705 (6).

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50

Böhm, Stanislav, and Josef Kuthan. "Quantum chemical prediction of 2H-pyran vibration spectrum." Collection of Czechoslovak Chemical Communications 55, no. 1 (1990): 10–20. http://dx.doi.org/10.1135/cccc19900010.

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Ab initio MO optimalization of the 2H-pyran molecule leads to a defined equilibrium geometry of this so far not identified heterocyclic molecule and to a physical justification of its existence. More advanced nonempirical wavefunctions and temperature corrections indicate that heterocyclic molecule I is energetically less stable than non-cyclic isomers II and III. Wavenumbers of fundamental vibrational transitions of heterocycle I and also known (2E)-2,4-pentadienal (IIIb were calculated using 3-21 G wavefunctions. The vibrational spectrum of compound I is predicted on the basis of correlation corrections.

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