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

Abstract

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.

Synergistic Lewis–Brønsted Acid Catalysis in Cascade Cyclization of ortho-Alkynylaryl Cyclopropylketones for the Synthesis of 2,3-Dihydronaphtho[1,2-b]furans

“…Initially, compound 1a was treated with 5 mol % of AgOTf and 2.0 equiv of H 2 O in DCE at room temperature. In this step, the reaction needed stirring for 0.5 h to enable a full conversion of substrate to the 1,5-diketone intermediate . To activate the cyclization process, we envisioned that addition of acids could help activate the 1,5-diketone intermediate.…”

“…Table demonstrated a comparison of conditions between a previously reported method and our current protocol. Over the past several years, our research group has been interested in the utilization of silver-catalyzed annulation of ortho -alkynylarylketone derivatives to create a variety of important polycyclic compounds . We therefore aimed to search for new conditions which could convert substrates 1 to naphthofuran derivatives 2 employing a lower amount of catalyst loading with a shorter reaction time.…”

Harnessing the power of natural alkaloids: the emergent role in epilepsy therapy

“…Quinoline alkaloids, identified by their fundamental quinoline ring structure, constitute a unique group of natural compounds primarily produced through the ortho-aminobenzoic acid pathway ( Thongsornkleeb et al, 2022 ). These alkaloids are widespread in Hemerocallis fulva (L.), Rutaceae Juss (often mistakenly called the “Dove family”), and especially in the Cinchona genus of the Rubiaceae Juss family.…”

Synthesis of Tetrahydro-5H-indolo[2,3-b]quinolines through Copper-Catalyzed Cascade Reactions of Aza-o-quinone Methides with Indoles

“…Tetracyclic indoloquinolines are an important class of organic molecules existing in a wide variety of natural products and bioactive molecules . In particular, indolo­[2,3- b ]­quinolines are privileged structural scaffolds of tetracyclic indoloquinolines since they have been well established to be useful as a potent topoisomerase I and II inhibitor, anti-inflammatory, antifungal, antiplasmodial, antibacterial, potent antiparasitic, antiproliferative, antitumor agents, such as communesin B, perophoramidine, and neocryptolepine, etc.…”