Cyanobacterial Metabolite Calothrixins: Recent Advances in Synthesis and Biological Evaluation

Abstract

The marine environment is host to unparalleled biological and chemical diversity, making it an attractive resource for the discovery of new therapeutics for a plethora of diseases. Compounds that are extracted from cyanobacteria are of special interest due to their unique structural scaffolds and capacity to produce potent pharmaceutical and biotechnological traits. Calothrixins A and B are two cyanobacterial metabolites with a structural assembly of quinoline, quinone, and indole pharmacophores. This review surveys recent advances in the synthesis and evaluation of the biological activities of calothrixins. Due to the low isolation yields from the marine source and the promise this scaffold holds for anticancer and antimicrobial drugs, organic and medicinal chemists around the world have embarked on developing efficient synthetic routes to produce calothrixins. Since the first review appeared in 2009, 11 novel syntheses of calothrixins have been published in the efforts to develop methods that contain fewer steps and higher-yielding reactions. Calothrixins have shown their potential as topoisomerase I poisons for their cytotoxicity in cancer. They have also been observed to target various aspects of RNA synthesis in bacteria. Further investigation into the exact mechanism for their bioactivity is still required for many of its analogs.

Benzo[b]carbazolediones Synthesis and Inhibitory Effects on Nucleotide Pyrophosphatases/Phosphodiesterases

“…In particular, benzo[ b ]carbazolediones are of considerable medicinal relevance, due to their specific biological activities . In 1999, calothrixin was reported as an excellent inhibitor against human Hela cancer cells, while Ellipticine quinone shows antimalarial and cytotoxic properties ( Figure ) . Thus, several synthetic approaches to benzocarbazolediones have been developed, including palladium(II) catalyzed oxidative biaryl coupling, radical cyclization reactions, anionic cycloaddition, Fischer indole cyclization or C,N‐dialkylation of enaminones…”

The Enhanced Catalytic Performance and Stability of Rh/γ-Al2O3 Catalyst Synthesized by Atomic Layer Deposition (ALD) for Methane Dry Reforming

“…Catalysts play an important role in DRM reaction. The conventional preparation methods for these catalysts include incipient wetness impregnation (IWI), precipitation, and colloidal synthesis [ 13 , 14 , 15 ]. Recently, atomic layer deposition (ALD) has also been used to synthesize heterogeneous catalysts [ 16 , 17 , 18 , 19 , 20 , 21 ].…”

Palladium-Catalyzed Dehydrogenative Coupling: An Efficient Synthetic Strategy for the Construction of the Quinoline Core

“…On the other hand, quinstatins, derived from dolastatin 10 (exceptionally anticancer drug contained in the sea hare Dolabella auricularia ) by replacing the C-terminal dolaphenine (Doe) unit with a carefully designed quinoline, have been reported to be exceptional cancer cell growth inhibitors [ 16 , 17 ]. Cyanobacterial metabolites calothrixins have shown their potential as human DNA topisomerase I poisons for their cytotoxicity in cancer [ 18 ].…”