Discovery of tetrahydrocarbazoles as dual pERK and pRb inhibitors

Design, synthesis and antimicrobial activity evaluation of novel tetrahydrocarbazole derivatives against phytopathogenic fungi and bacteria

BACKGROUND

Plant pathogenic bacteria and fungi had a wide impact on various crops and caused serious economic losses. Compared to traditional antibiotics and fungicides, alkaloids are noteworthy for their significant biological activities. Tetrahydrocarbazole (THCz) was widely present in many indole alkaloids and had various pharmacological activities. This study used Fischer indole synthesis method and fragment splicing strategy to design and synthesize a novel drug like chemical entity based on THCz alkaloid guidance, evaluated the antimicrobial activities of these derivatives against plant pathogenic bacteria and fungi and discussed the structure-activity relationship.

RESULTS

Among these derivatives, compound KZa-17 displayed good antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri, Pseudo-monas sollamacearum and Erwinia aroideae. The MIC90 values were 3.12, 1.56, 6.25, 12.5 μg/mL, respectively, which were better than the positive control drugs thiodiazole copper and bismerthiazol. The results of in vivo antibacterial activity test showed that the protective effect of compound KZa-17 on rice at 200 μg/mL was 32.76%, which was better than that of thiodiazole copper (24.73%). The biochemical experiments showed that compound KZa-17 could inhibit biofilm formation of Xoo, reduce drug resistance and pathogenicity of bacteria, damage cell membrane integrity, increase permeability, and cause oxidative stress damage.

CONCLUSION

Most of the newly synthesized derivatives based on THCz alkaloid guidance showed favorable antimicrobial effects. In particular, compound KZa-17 can be used as a candidate lead compound for further structural optimization and development. © 2024 Society of Chemical Industry.

A Review on Carbazole and Its Derivatives as Anticancer Agents From 2013 to 2024

Carbazole, a natural alkaloid, has been recognized as an effective anticancer agent for over 40 years. However, only a limited number of carbazole-based compounds have received FDA approval for cancer treatment. Current cancer therapies are often associated with significant side effects, causing physical, emotional, and financial burdens for patients. Additionally, despite advancements, cancer prevention and treatment remain challenging due to suboptimal clinical outcomes. The development of new drugs is crucial for achieving safer and more effective cancer therapies. This review focuses on various carbazole derivatives and hybrid composites, highlighting their interactions with distinct receptors and their mechanisms of anticancer action, along with a general structure-activity relationship (SAR). It also emphasizes carbazole-based compounds employed in chemoprevention, which aim to delay or prevent malignant progression. By covering carbazole derivatives and their anticancer potential from 2013 to the present, along with their current clinical status, this study offers valuable insights and updates for researchers in the field.

Antifungal Tetrahydrocarbazole Compound CAR-8 Induces Endoplasmic Reticulum Stress in Candida albicans

The development of new effective antifungal agents is essential to combat fungal infections. Tetrahydrocarbazole has been exploited as a promising skeleton against various pathogenic microorganisms and is used to search for novel active antifungal compounds. In this study, a library composed of small tetrahydrocarbazole compounds was screened, and a potent antifungal agent, CAR-8, was identified with a minimum inhibitory concentration of 2-4 μg/mL against Candida albicans. CAR-8 showed strong fungicidal activities and killed almost all C. albicans within 3 h at a concentration of 16 μg/mL. At concentrations of 2 and 8 μg/mL, CAR-8 significantly inhibited the formation of hyphae and biofilms. Moreover, CAR-8 at 10 and 20 mg/kg reduced the fungal load and improved the survival in the C. albicans infection model in the invertebrate Galleria mellonella. Transcriptome analysis revealed significant changes in the expression of genes associated with protein processing in the endoplasmic reticulum (ER), ER-associated degradation, and unfolded protein response (UPR), which suggested that CAR-8 treatment induced ER stress. Moreover, CAR-8 treatment resulted in various phenotypes similar to tunicamycin, a classical ER stress inducer. These included nonconventional splicing of HAC1 mRNA, the fragmented morphology of ER, the distribution changes of GFP-Snc1 in Saccharomyces cerevisiae, and cell apoptosis probably caused by ER stress. More importantly, the disruption of IRE1 or HAC1 increased the sensitivity of C. albicans to CAR-8, confirming that the UPR signaling pathway was critical for CAR-8 resistance. Overall, our study identifies a potent ER stress-induced antifungal compound that will help the discovery of new antifungal drugs.

Brønsted Acid-Catalyzed Synthesis of 4-Functionalized Tetrahydrocarbazol-1-ones from 1,4-Dicarbonylindole Derivatives

A p-toluenesulfonic acid-catalyzed cascade reaction is reported for the synthesis of 4-functionalized tetrahydrocarbazolones via the reaction of 4-(indol-2-yl)-4-oxobutanal derivatives with a variety of nucleophiles in acetonitrile or hexafluoroisopropanol. After the initial intramolecular Friedel-Crafts hydroxyalkylation, the 3-indolylmethanol intermediate is subsequently activated and reacted with the external nucleophile. The reaction conditions are crucial to avoid alternative reaction pathways, allowing direct substitution reaction with thiols, (hetero)arenes, alkenes, or sulfinates. The procedure features high overall yields to access a diverse family of compounds bearing the tetrahydrocarbazole core.

A palladium-catalyzed Barluenga cross-coupling - reductive cyclization sequence to substituted indoles

A short and flexible synthesis of substituted indoles employing two palladium-catalyzed reactions, a Barluenga cross-coupling of p-tosylhydrazones with 2-nitroarylhalides followed by a palladium-catalyzed, carbon monoxide-mediated reductive cyclization has been developed. A one-pot, two-step methodology was further developed, eliminating isolation and purification of the cross-coupling product. This was accomplished by utilizing the initially added 0.025 equivalents of bis(triphenylphosphine)palladium dichloride, thus serving a dual role in the cross-coupling and the reductive cyclization. It was found that addition of 1,3-bis(diphenylphosphino)propane and carbon monoxide after completion of the Barluenga reaction afforded, in most cases, significantly better overall yields.

Design, step-economical diversity-oriented synthesis of an N-heterocyclic library containing a pyrimidine moiety: discovery of novel potential herbicidal agents

The synthesis of highly diverse libraries has become of paramount importance for obtaining novel leads for drug and agrochemical discovery. Herein, the step-economical diversity-oriented synthesis of a library of various pyrimidine-N-heterocycle hybrids was developed, in which a 4,6-dimethoxypyrimidine core was incorporated into nine kinds of N-heterocycles. A total of 34 structurally diverse compounds were synthesized via a two-step process from very simple and commercially available starting materials. Further, in vivo biological screening of this library identified 11 active compounds that exhibited good post-emergence herbicidal activity against D. sanguinalis at 750 g ai per ha. More importantly, pyrimidine-tetrahydrocarbazole hybrid 5q showed good to excellent herbicidal activity against five test weeds at the same dosage. Pyrimidine-tetrahydrocarbazole hybrids represent a novel class of herbicidal agents that may become promising lead compounds in the herbicidal discovery process.

Chemospecific Cyclizations of α-Carbonyl Sulfoxonium Ylides on Aryls and Heteroaryls

The functionalization of aryl and heteroaryls using α-carbonyl sulfoxonium ylides without the help of a directing group has remained so far a neglected area, despite the advantageous safety profile of sulfoxonium ylides. Described herein are the cyclizations of α-carbonyl sulfoxonium ylides onto benzenes, benzofurans and N-p-toluenesulfonyl indoles in the presence of a base in HFIP, whereas pyrroles and N-methyl indoles undergo cyclization in the presence of an iridium catalyst. Significantly, these two sets of conditions are chemospecific for each groups of substrates.