Highly efficient one-pot synthesis of D-ring chloro-substituted neocryptolepines via a condensation—Pd-catalyzed intramolecular direct arylation strategy

A new synthesis of indolo[2,3-b]quinolines from 3-acetyl-N-alkyl-2-chloroindoles with 2-aminobenzophenone

A new synthesis of N-alkyl- and 11-phenyl-modified indolo[2,3-b]quinolines was achieved via PEG-400-promoted and visible light-induced one-step reaction of 3-acetyl-N-alkyl-2-chloroindoles with 2-aminobenzophenone in 40% methanol aqueous solution. The merits of the protocol include cost efficiency, convenience, and eco- and user-friendliness.

Indoloquinoline Alkaloids as Antimalarials: Advances, Challenges, and Opportunities

Malaria infections affect almost half of the world's population, with over 200 million cases reported annually. Cryptolepis sanguinolenta, a plant native to West Africa, has long been used across various regions of Africa for malaria treatment. Chemical analysis has revealed that the plant is abundant in indoloquinolines, which have been shown to possess antimalarial properties. Cryptolepine, neocryptolepine, and isocryptolepine are well-studied indoloquinoline alkaloids known for their potent antimalarial activity. However, their structural rigidity and associated cellular toxicity are major drawbacks for preclinical development. This review focuses on the potential of indoloquinoline alkaloids (cryptolepine, neocryptolepine, and isocryptolepine) as scaffolds in drug discovery. The article delves into their antimalarial effects in vitro and in vivo, as well as their proposed mechanisms of action and structure-activity relationship studies. Several studies aim to improve these leads by reducing cytotoxicity while preserving or enhancing antimalarial activity and gaining insights into their mechanisms of action. These investigations highlight the potential of indoloquinolines as a scaffold for developing new antimalarial drugs.

A Compilation of Synthetic Strategies to Access the Most Utilized Indoloquinoline Motifs

Indoloquinoline alkaloids constitute an important class of aromatic heterocycles consisting of quinoline and indole fused together in various orientations. These compounds, both natural and synthetic, often display various bioactivities which have established them to be one of the interesting medicinal targets. This class of compounds have stimulated much interest among synthetic and medicinal chemists as evidenced by growth in the number of synthetic methods to prepare and study this class of alkaloids. This review compiles the synthetic strategies and methods currently known in the literature for the construction of four important indoloquinoline skeletons.

Triflic acid-mediated N-heteroannulation of β-anilino-β-(methylthio)acrylonitriles: a facile synthesis of 4-amino-2-(methylthio)quinolines

Various functionalised 4-amino-2-(methylthio)quinolines are synthesised through triflic acid-mediated N-heteroannulation of α-functionalized-β-anilino-β-(methylthio)acrylonitriles for the first time. The N-heteroannulation process is highly chemoselective and has mild reaction conditions. However, this process fails in the absence of the β-methylthio group in the acrylonitriles. In addition, a new double N-heteroannulation process is demonstrated to synthesise indolo[3,2-c]quinolines from non-heterocyclic precursors. Natural product isocryptolepine is synthesised in four steps from an acyclic precursor.

Efficient total synthesis of neocryptolepine and synthetic access to 6-methylquinindoline from a common intermediate

The total synthesis of neocryptolepine and the synthesis of its non-natural isomer 6-methyl quinindoline were efficiently achieved in a few steps from a common intermediate.

Copper-catalyzed three-component reaction: solvent-controlled regioselective synthesis of 4-amino- and 6-amino-2-iminopyridines

Regioselective synthesis of multisubstituted 4-amino- and 6-amino-2-iminopyridines has been developed via the copper-catalyzed three-component reaction based on the reaction conditions selection. The reaction of sulfonyl azides, alkynes, and 2-[(amino)methylene]malononitriles catalyzed by copper(I) iodide in tetrahydrofuran at room temperature afforded substituted 4-amino-2-iminopyridines, whereas, in N,N-dimethylformamide at 50 °C under N2, it generated substituted 6-amino-2-iminopyridines as predominant products.

An intramolecular inverse electron demand Diels-Alder approach to annulated α-carbolines

Intramolecular inverse electron demand cycloadditions of isatin-derived 1,2,4-triazines with acetylenic dienophiles tethered by amidations or transesterifications proceed in excellent yields to produce lactam- or lactone-fused α-carbolines. Beginning with various isatins and alkynyl dienophiles, a pilot-scale library of eighty-eight α-carbolines was prepared by using this robust methodology for biological evaluation.