Search results for "cycle"
showing 10 items of 3119 documents
The “nitrogen effect” : Complexation with macrocycles potentiates fused heterocycles to form halogen bonds in competitive solvents
2023
Weak intermolecular forces are typically very difficult to observe in highly competitive polar protic solvents as they are overwhelmed by the quantity of competing solvent. This is even more challenging for three-component ternary assemblies of pure organic compounds. In this work, we overcome these complications by leveraging the binding of fused aromatic N-heterocycles in an open resorcinarene cavity to template the formation of a three-component halogen-bonded ternary assembly in a protic polar solvent system. peerReviewed
Resource, environmental and economic considerations in the development of a Reverse Electrodialysis Heat Engine
The RED Heat Engine operates as a closed-loop RED system, where limited amounts of artificial saline solutions are used as working fluids. The solutions exiting from the RED unit are regenerated by means of a separation step, which uses low-temperature heat as its energy source. Essentially the system converts low-grade heat to electricity. There are two main alternative regeneration strategies: (i) extract solvent from the high salinity solution and move it to the low salinity solution or (ii) extract salt from the low salinity solution and move it to the high salinity solution. In this thesis are considered the Multi-effect distillation (MED) and the Membrane Distillation (MD) under the s…
One‐pot synthesis of [2+2]‐helicate‐like macrocycle and 2+4‐μ4‐oxo tetranuclear open frame complexes : Chiroptical properties and asymmetric oxidativ…
2020
Synthesis of binuclear Cu(II) terminally closed [2+2]‐ double‐stranded helicate‐like macrocycles 1, 1′,1″, 2, 2′, 2″ and 2+4‐μ4‐oxo tetranuclear open frame complexes 3, 3′, 3″, 4, 4′, 4″ are established. Adapting one‐pot self‐assembly technique from simple three components systems: 1,1′‐binaphthyl‐2,2′‐diamine, 4‐methyl‐2,6‐diformyl phenol and cupric salts, the helicate‐like [2+2]‐ macrocyclic complexes 1–1″, 2–2″ and 2+4‐μ4‐oxo tetranuclear complexes 3–3″, 4–4″ were obtained by appropriately altering the reaction condition such as temperature and subcomponent ratio. Density Functional Theory (DFT) calculations were carried out for understanding the structural geometries, intermediates invo…
Induction of apoptosis by the proteasome inhibitor MG132 in human HCC cells: Possible correlation with specific caspase-dependent cleavage of β-caten…
2004
Proteasome inhibitors, like MG132, can exert cell growth inhibitory and apoptotic effects in different tumor types. The apoptotic mechanism of these compounds involves the activation of the effector caspases. beta-catenin, also an oncogene, represents one of the substrates of these proteases, but the consequences of its cleavage are poorly understood. We investigated its function during apoptosis induced by MG132 in three hepatocellular carcinoma (HCC) cell lines, endowed (HepG2 and HuH-6) or not (HA22T/VGH) with activating mutations of beta-catenin. Induction of apoptosis was associated with cell growth inhibition, accumulation of the cells at the G(2)/M phases of the cell cycle, as well a…
Editorial: Emerging heterocycles as bioactive compounds
2023
Heterocycles represent a privileged scaffold due to their ability to interact with biological systems via heteroatoms. It is no coincidence that every year the Food and Drug Administration approves numerous new drugs that contain at least one heterocyclic system as active pharmacophoric part in their structure. Many heterocyclic compounds with therapeutic properties, including anticancer, antimicrobial, anti-inflammatory and so on, come from natural sources such as plants and animals, and medicinal chemists very often use them to study their chemical space and improve their biological activity. In fact, several efficient approaches for the formation of aromatic heterocyclic compounds and th…
Asymmetric Synthesis of Fluorinated Isoindolinones through Palladium-Catalyzed Carbonylative Amination of Enantioenriched Benzylic Carbamates
2015
The asymmetric synthesis of fluorinated isoindolinones has been achieved by a palladium-catalyzed aminocarbonylation reaction of the corresponding -fluoroalkyl o-iodobenzylamines. A base-mediated anti -hydride elimination process was suggested to explain the partial erosion of the optical purity observed in some cases. This mechanistic rationale enabled the minimization of this partial racemization by fine-tuning the pK(a) of the base.
Organocatalytic approach to benzofused nitrogen-containing heterocycles: enantioselective total synthesis of (+)-angustureine.
2008
Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones
2014
The cyclocondensation of enones with aminoacetonitrile furnishes 3,4-dihydro-2H-pyrrole-2-carbonitriles which can be readily converted to 2,4-disubstituted pyrroles by microwave-induced dehydrocyanation. Alternatively, oxidation of the intermediates produces 3,5-disubstituted pyrrole-2-carbonitriles.
Traceless chirality transfer from a norbornene β-amino acid to pyrimido[2,1-a]isoindole enantiomers
2017
The synthesis of two enantiomeric pairs of pyrimidoisoindoles 9a, 9b and 10a, 10b is reported. During a domino ring-closure reaction, followed by cycloreversion, the chirality of diendo-(−)-(1R,2S,3R,4S)-3-aminobicyclo[2.2.1]hept-5-ene-2-carboxamide [(−)-1] was successfully transfered to heterocycles (+)-9a, (+)-10a, (−)-9b, (−)-10b and (−)-10c. peerReviewed
Scalable (Enantioselective) Syntheses of Novel 3-Methylated Analogs of Pazinaclone, (S)-PD172938 and Related Biologically Relevant Isoindolinones
2022
Herein, we report the application of an efficient and practical K2CO3 promoted cascade reaction of 2-acetylbenzonitrile in the synthesis of novel 3-methylated analogs of Pazinaclone and PD172938, belonging to isoindolinones heterocyclic class bearing a tetrasubstituted stereocenter. Organocatalytic asymmetric synthesis of the key intermediate and its transformation into highly enantioenriched 3-methylated analog of (S)-PD172938 was also developed. These achievements can be of particular interest also for medicinal chemistry, since the methyl group is a very useful structural modification in the rational design of new and more effective bioactive compounds.