Marine pyrrolocarbazoles and analogues: synthesis and kinase inhibition

Harnessing bacterial metabolites for enhanced cancer chemotherapy: unveiling unique therapeutic potentials

Cancer poses a serious threat to health globally, with millions diagnosed every year. According to Global Cancer Statistics 2024, about 20 million new cases were reported in 2022, and 9.7 million people worldwide died of this condition. Advanced therapies include combination of one or more treatment procedures, depending on the type, stage, and particular genetic constitution of the cancer, which may include surgery, radiotherapy, chemotherapy, immunotherapy, hormone therapy, targeted therapy, and stem cell transplant. Also, awareness about lifestyle changes, preventive measures and screening at early stages has reduced the incidence of the disease; still, there is a major failure in controlling the incidence of cancer because of its complex and multifaceted nature. With increasing interest in bacterial metabolites as possible novel and effective treatment options in cancer therapy, their main benefits include not only direct anticancer effects but also the modulation of the immune system and potential for targeted and combination therapies. They can therefore be used in combination with chemotherapy, radiotherapy, or immunotherapy to improve outcomes or reduce side effects. Furthermore, nanoparticle-based delivery systems have the potential to enhance the potency and safety of anticancer drugs by providing improved stability, targeted release, and controlled delivery.

Phosphine-Catalyzed (4 + 2) Annulation of Allenoates Bearing Acidic Hydrogen with 1,1-Dicyanoalkenes

α-succinimide-substituted allenoates were employed as phosphine acceptors in phosphine-catalyzed (4 + 2) annulation with 1,1-dicyanoalkenes. They served as C4 synthons in the annulation reaction under mild reaction conditions and produced hexahydroisoindole derivatives in moderate to high yields with good to excellent diastereoselectivities.

Pd-Catalyzed Sequential Electrophilic Cyclization/Selective C-H Annulation Cascade: Synthesis of Isoxazole-Phthalimide-Fused Poly-Heterocyclics

Harnessing the organo-palladium intermediates generated from electrophilic cyclizations for tandem C-C bond construction is a challenging task but constitutes an excellent tool for constructing complex motifs from simpler substrates. We realize herein such a cyclative annulation of alkynyl-oxime ethers with maleimides for the facile construction of isoxazole-phthalimide hybrid motifs through Pd(II) catalysis. This protocol features excellent regio-selectivity in C-H selection, a broad substrate scope, good functional group tolerance, and scalability. Necessary KIE & labeling studies give insight into the reaction mechanism.

[RhCp*Cl2]2-Catalyzed Indole Functionalization: Synthesis of Bioinspired Indole-Fused Polycycles

Polycyclic fused indoles are ubiquitous in natural products and pharmaceuticals due to their immense structural diversity and biological inference, making them suitable for charting broader chemical space. Indole-based polycycles continue to be fascinating as well as challenging targets for synthetic fabrication because of their characteristic structural frameworks possessing biologically intriguing compounds of both natural and synthetic origin. As a result, an assortment of new chemical processes and catalytic routes has been established to provide unified access to these skeletons in a very efficient and selective manner. Transition-metal-catalyzed processes, in particular from rhodium(III), are widely used in synthetic endeavors to increase molecular complexity efficiently. In recent years, this has resulted in significant progress in reaching molecular scaffolds with enormous biological activity based on core indole skeletons. Additionally, Rh(III)-catalyzed direct C-H functionalization and benzannulation protocols of indole moieties were one of the most alluring synthetic techniques to generate indole-fused polycyclic molecules efficiently. This review sheds light on recent developments toward synthesizing fused indoles by cascade annulation methods using Rh(III)-[RhCp*Cl2]2-catalyzed pathways, which align with the comprehensive and sophisticated developments in the field of Rh(III)-catalyzed indole functionalization. Here, we looked at a few intriguing cascade-based synthetic designs catalyzed by Rh(III) that produced elaborate frameworks inspired by indole bioactivity. The review also strongly emphasizes mechanistic insights for reaching 1-2, 2-3, and 3-4-fused indole systems, focusing on Rh(III)-catalyzed routes. With an emphasis on synthetic efficiency and product diversity, synthetic methods of chosen polycyclic carbocycles and heterocycles with at least three fused, bridged, or spiro cages are reviewed. The newly created synthesis concepts or toolkits for accessing diazepine, indol-ones, carbazoles, and benzo-indoles, as well as illustrative privileged synthetic techniques, are included in the featured collection.

A Versatile Pd-Catalyzed Alkyne Annulation Process for Benzo[a]carbazoles and their Anticancer Analogues

A Pd-catalyzed, simple, and divergent approach for the direct synthesis of benzo[a]carbazoles from internal alkynes and N-tosyl-iodoindoles has been demonstrated. This methodology highlights the influences of reaction media and temperature for the synthesis of either N-protected or N-deprotected benzo[a]carbazoles. This cascade strategy provides a series of electronically different benzo[a]carbazoles with good yields. The synthesized benzo[a]carbazoles were evaluated for in vitro anticancer activity against human lung cancer A549 cells and human breast cancer MDA-MB-231 cells. Notably, two of the representative analogues displayed potent anticancer activity against both cancer cell lines.

Development and validation of HPLC method for analysis of indolocarbazole derivative LCS-1269

Indolocarbazole glycosidic derivative LCS-1269 with significant antiproliferative activity has been synthesized in N.N. Blokhin National Medical Research Center of Oncology. To control the quality of the substance, the chromatographic method of the assay was created and validated. The technique was carried out in a gradient mode using mobile phases consist of acetonitrile, trifluoroacetic acid and purified water. The specificity of the method was shown by checking of test solutions and the special solvent chromatograms. The method linearity was confirmed, and the parameters of linear dependence have been estimated, and the relationship was described by the equation: y = 49.23× – 35.51 with correlation coefficient 0.9998. The method’s precision was determined as the repeatability with a relative error of the mean 1.49% and was 2.433 ± 0.036. Was shown, that the results obtained in the intermediate precision estimation were not burdened with a systematic error. The detection limit and quantitation limit were calculated based on the linear relationship data as 3.15 μg/mL and 9.57 μg/mL, respectively. Sensitive HPLC method for LCS-1269 assay in substance has been developed and validated.

Retracted Article: The synthesis and biological activity of marine alkaloid derivatives and analogues

The ocean is the origin of life, with a unique ecological environment, which has given birth to a wealth of marine organisms. The ocean is an important source of biological resources and tens of thousands of monomeric compounds have been separated from marine organisms using modern separation technology. Most of these monomeric compounds have some kind of biological activity that has attracted extensive attention from researchers. Marine alkaloids are a kind of compound that can be separated from marine organisms. They have complex and special chemical structures, but at the same time, they can show diversity in biological activities. The biological activities of marine alkaloids mainly manifest in the form of anti-tumor, anti-fungus, anti-viral, anti-malaria, and anti-osteoporosis properties. Many marine alkaloids have good medicinal prospects and can possibly be used as anti-tumor, anti-viral, and anti-fungal clinical drugs or as lead compounds. The limited amounts of marine alkaloids that can be obtained by separation, coupled with the high cytotoxicity and low selectivity of these lead compounds, has restricted the clinical research and industrial development of marine alkaloids. Marine alkaloid derivatives and analogues have been obtained via rational drug design and chemical synthesis, to make up for the shortcomings of marine alkaloids; this has become an urgent subject for research and development. This work systematically reviews the recent developments relating to marine alkaloid derivatives and analogues in the field of medical chemistry over the last 10 years (2010-2019). We divide marine alkaloid derivatives and analogues into five types from the point-of-view of biological activity and elaborated on these activities. We also briefly discuss the optimization process, chemical synthesis, biological activity evaluation, and structure-activity relationship (SAR) of each of these compounds. The abundant SAR data provides reasonable approaches for the design and development of new biologically active marine alkaloid derivatives and analogues.

Synthesis of maleimide fused benzocarbazoles and imidazo[1,2-a]pyridines via rhodium(iii)-catalyzed [4 + 2] oxidative cycloaddition

In this paper, an efficient and sustainable synthesis of maleimide-fused benzocarbazoles/imidazo[1,2-a]pyridines from the reaction of 2-arylindoles/2-arylimidazo[1,2-a]pyridines with maleimides through oxidative [4 + 2] annulation is presented.

Annulative π-extension of indoles and pyrroles with diiodobiaryls by Pd catalysis: rapid synthesis of nitrogen-containing polycyclic aromatic compounds

A palladium-catalyzed one-step annulative π-extension (APEX) reaction of indoles and pyrroles that allows rapid access to nitrogen-containing polycyclic aromatic compounds is described. In the presence of palladium pivalate and silver carbonate, diverse indoles or pyrroles coupled with diiodobiaryls in a double direct C-H arylation manner to be transformed into the corresponding π-extended compounds in a single step. The newly developed catalytic system enables the use of various pyrroles and indoles as templates with a series of diiodobiaryls to provide structurally complicated and largely π-extended nitrogen-containing polycyclic aromatic compounds that are otherwise difficult to synthesize.

Ascidian Toxins with Potential for Drug Development

Ascidians (tunicates) are invertebrate chordates, and prolific producers of a wide variety of biologically active secondary metabolites from cyclic peptides to aromatic alkaloids. Several of these compounds have properties which make them candidates for potential new drugs to treat diseases such as cancer. Many of these natural products are not produced by the ascidians themselves, rather by their associated symbionts. This review will focus mainly on the mechanism of action of important classes of cytotoxic molecules isolated from ascidians. These toxins affect DNA transcription, protein translation, drug efflux pumps, signaling pathways and the cytoskeleton. Two ascidian compounds have already found applications in the treatment of cancer and others are being investigated for their potential in cancer, neurodegenerative and other diseases.

Kinase inhibitors from marine sponges

Protein kinases play a critical role in cell regulation and their deregulation is a contributing factor in an increasing list of diseases including cancer. Marine sponges have yielded over 70 novel compounds to date that exhibit significant inhibitory activity towards a range of protein kinases. These compounds, which belong to diverse structural classes, are reviewed herein, and ordered based upon the kinase that they inhibit. Relevant synthetic studies on the marine natural product kinase inhibitors have also been included.