Mild, efficient Fischer indole synthesis using 2,4,6-trichloro-1,3,5-triazine (TCT)

Pyrrole: A Decisive Scaffold for the Development of Therapeutic Agents and Structure-Activity Relationship

An overview of pyrroles as distinct scaffolds with therapeutic potential and the significance of pyrrole derivatives for drug development are provided in this article. It lists instances of naturally occurring pyrrole-containing compounds and describes the sources of pyrroles in nature, including plants and microbes. It also explains the many conventional and modern synthetic methods used to produce pyrroles. The key topics are the biological characteristics, pharmacological behavior, and functional alterations displayed by pyrrole derivatives. It also details how pyrroles are used to treat infectious diseases. It describes infectious disorders resistant to standard treatments and discusses the function of compounds containing pyrroles in combating infectious diseases. Furthermore, the review covers the uses of pyrrole derivatives in treating non-infectious diseases and resistance mechanisms in non-infectious illnesses like cancer, diabetes, and Alzheimer's and Parkinson's diseases. The important discoveries and probable avenues for pyrrole research are finally summarized, along with their significance for medicinal chemists and drug development. A reference from the last two decades is included in this review.

Spectroscopic, crystallographic, and Hirshfeld surface characterization of nine-membered-ring-containing 9-meth-oxy-3,4,5,6-tetra-hydro-1H-benzo[b]azonine-2,7-dione and its parent tetra-hydro-car-ba-zole

9-Meth-oxy-3,4,5,6-tetra-hydro-1H-benzo[b]azonine-2,7-dione, C13H15NO3, (I), and 6-meth-oxy-1,2,3,4-tetra-hydro-car-ba-zole, C13H15NO, (II), represent the structures of a benzoazonine that contains a nine-membered ring and its parent tetra-hydro-car-ba-zole. The mol-ecules of (I) pack together via strong amide N-H⋯O hydrogen bonding and weak C-H⋯O inter-actions, whereas the parent tetra-hydro-car-ba-zole (II) packs with C/N-H⋯π inter-actions, as visualized by Hirshfeld surface characterization.

Palladium-Catalyzed Asymmetric Hydrogenation of Unprotected 3-Substituted Indoles

A palladium-catalyzed asymmetric hydrogenation of unprotected 3-substituted indoles was developed, providing a series of 3-substituted indolines in excellent yields with ≤94.4:5.6 er. The large sterically hindered bisphosphine ligand played a crucial role in the enantioselective control. In addition, the gram-scale hydrogenation experiment and product derivatizations were performed successfully.

In-depth characterization of nitrogen heterocycles of petroleum by liquid chromatography-energy-resolved high resolution tandem mass spectrometry

With the increased attention to processing heavy crude oils, a detailed description of chemical composition is critical for the petroleum refining industry. The current analytical technique such as ultrahigh resolution mass spectrometry has been successfully applied for the molecular level characterization of complex petroleum fractions. But the structural characterization of heavy petroleum feedstock is still a great challenge. In this study, a novel in-depth characterization method of nitrogen heterocycles (N-heterocycles) in heavy petroleum mixtures was proposed by online liquid chromatography coupled with electrospray ionization high resolution energy-resolved mass spectrometry. A series of typical basic aromatic, neutral aromatic and naphtheno-aromatic nitrogen heterocyclic model compounds were synthesized to investigate energy-resolved fragmentation behaviors in high energy collision-induced dissociation at 10-100 eV. Energy-dependent fragmentation pathways were elucidated. Notably, characteristic double bond equivalent (DBE) versus carbon number distributions of N₁ ions and all CH ions were discovered, which were closely related to their core structure. Then a workflow to assign core structures of alkyl-substituted N-heterocycles in petroleum was proposed and validated. The developed method was applied to investigate the structural isomers in feed and product vacuum gas oil (VGO) fractions. Core structural differences in feed VGO and subtle structural variations between feed and product VGOs were recognized. This work can distinguish structural isomers of N-heterocycles with the subtle difference in their core structure in heavy petroleum fractions based on global energy dimensional fragmentation characteristics.

Antischistosomal tetrahydro-γ-carboline sulfonamides

We discovered tetrahydro-γ-carboline sulfonamides as a new antischistosomal chemotype. The aryl sulfonamide and tetrahydro-γ-carboline substructures were required for high antischistosomal activity. Increasing polarity improved solubility and metabolic stability but decreased antischistosomal activity. We identified two compounds with IC₅₀ values <5 µM against ex vivo Schistosoma mansoni.

Water Modulated Diastereoselective Synthesis of cis/trans-Spiro[indoline-3,6'-naphtho[2,3-c]carbazoles]

p-TsOH catalyzed Diels-Alder reaction of 2-(1-alkylindol-3-yl)naphthalene-1,4-diones and 3-phenacylideneoxindoles showed fascinating diastereoselectivity. The reaction with the hydrated p-TsOH afforded trans-isomers of dihydrospiro[indoline-3,6'-naphtho[2,3-c]carbazoles] as major products. Alternatively, the reaction with anhydrous p-TsOH under a Dean and Stark apparatus predominately gave cis-isomer of dihydrospiro[indoline-3,6'-naphtho[2,3-c]carbazoles]. On the other hand, the similar p-TsOH catalyzed reaction of 2-(indol-3-yl)naphthalene-1,4-diones with 3-arylideneindolin-2-ones afforded cis/trans-isomers of dihydrospiro[indoline-3,6'-naphtho[2,3-c]carbazoles]. Additionally, the p-TsOH catalyzed reaction of 2-(indol-3-yl)naphthalene-1,4-diones with 2-arylidene-1,3-indanediones gave the expected spiro[indene-2,6'-naphtho[2,3-c]carbazoles] in satisfactory yields.

Diastereoselective construction of carbazole-based spirooxindoles via the Levy three-component reaction

The CuSO₄ catalyzed three-component reaction of indole-2-acetate, aromatic aldehydes and 3-methyleneoxindoles in toluene at 130 °C afforded polysubstituted spiro[carbazole-3,3′-indolines] in good yields and with high diastereoselectivity.

Discovery of carbazole derivatives as novel allosteric MEK inhibitors by pharmacophore modeling and virtual screening

We report in this work the discovery of novel allosteric MEK inhibitors by pharmacophore modeling and virtual screening. Two out of 13 virtual hit compounds were identified as MEK kinase inhibitors using a MEK1 binding assay. Structural derivations on the hit compound M100 (IC50 = 27.2 ± 4.5 μM in RAF-MEK cascading assay) by substituent transformation and bioisosterism replacement have led to the synthesis of a small library of carbazoles. The enzymatic studies revealed the preliminary structure-activity relationships and the derivative 22k (IC50 = 12.8 ± 0.5 μM) showed the most potent inhibitory effect against Raf-MEK cascading. Compound 7 was discovered as toxic as M100 to tumor cells whereas safer to HEK293 cells (IC50 > 100 μM) than M100 (IC50 = 8.9 ± 2.0 μM). It suggests that carbazole is a good scaffold for the design of novel MEK inhibitors for therapeutic uses. More importantly, the developed pharmacophore model can serve as a reliable criterion in novel MEK inhibitor discovery.

Synthesis of topologically constrained naphthalimide appended palladium(ii)–N-heterocyclic carbene complexes – insights into additive controlled product selectivity

Pd(ii)–NHC catalyzed regioselective heteroannulation of o-haloanilines and arylethynyl-trimethylsilane to yield indoles and additive controlled switchable product selectivity has been demonstrated.

Diastereoselective synthesis and biological evaluation of enantiomerically pure tricyclic indolines

Tricyclic indolines are common in both natural products and synthetic chemical probes. In this study we demonstrated that enantiomerically pure tricyclic indolines can be prepared from an inexpensive commercially available chiral starting material, pyroglutamic acid. The synthesis features a highly diastereoselective gold-catalyzed cyclization of alkyne-tethered indoles and subsequent diastereoselective reductive ring-opening reaction. Using this approach, we synthesized analogs of our previously discovered tricyclic indoline probes that possess antibacterial and resistance-modifying activity. The biological activity against methicillin-resistant Staphylococcus aureus (MRSA) of these analogues was evaluated and reported. The synthetic approach reported may be leveraged in the future to prepare diastereopure chemical probes for the determination of biological targets for drug discovery.

Synthesis of 3-arylindole derivatives from nitroalkane precursors

3-Arylindole derivatives were synthesized by Cu(i) catalysed intramolecular Ullmann coupling of 2-bromoarylaminoalkanes.

Recent advances in the application of deep eutectic solvents as sustainable media as well as catalysts in organic reactions

This review highlights the recent advances using deep eutectic solvents (DESs), deep eutectic ionic liquids (DEILs), low-melting mixtures (LMMs) or low transition temperature mixtures (LTTMs) as green media as well as catalysts in organic reactions.

Metal-free synthesis of cyano acrylates via cyanuric chloride-mediated three-component reactions involving a cascade consists of Knoevenagel condensation/cyano hydration/esterification

The synthesis of cyano acrylates has been achieved via an organocatalytic domino Knoevenagel reaction, hydration and esterification under metal-free conditions without using any additional solvent.