Practical synthesis of indolopyrrolocarbazoles

Novel maleic anhydride derivatives: liquid crystalline materials with enhanced mesomorphic and optical characteristics

A new class of liquid crystalline materials, 4-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)phenyl 4-(alkoxy)benzoates (Mn), derived from maleic anhydride, was synthesized and studied for mesomorphic and optical properties. These materials consist of three derivatives with varying terminal flexible chain lengths (6-12 carbons) linked to the phenyl ring near the ester bond. The study employed differential scanning calorimetry and polarized optical microscopy (POM) to characterize the mesomorphic properties. Molecular structures were elucidated using elemental analysis, FT-IR, and NMR spectroscopy. The findings reveal that all the synthesized maleic anhydride derivatives exhibit enantiotropic nematic (N) mesophases. The insertion of the heterocyclic maleic anhydride moiety into the molecular structure influences the stability and range of the N phase. Additionally, entropy changes during N-isotropic transitions are of small magnitude and exhibit non-linear trends independent of the terminal alkoxy chain length (n). This suggests that the ester linkage group does not significantly promote molecular biaxiality, and the clearing temperature values are relatively high. By comparing the investigated materials with their furan derivatives found in existing literature, it was established that the substitution examined in this study induces the formation of nematic phases.

Bisindolyl Maleimides and Indolylmaleimide Derivatives-A Review of Their Synthesis and Bioactivity

The evolution of bisindolyl maleimides and indolyl maleimide derivatives and their unique biological activities have stimulated great interest in medicinal chemistry programs. Bisindolylmaleimide (BIM)-type compounds arise from natural sources such as arcyriarubin and are biosynthetically related to indolocarbazoles. BIMs are commonly the immediate synthetic precursors of indolocarbazoles, lacking a central bond between the two aromatic units and making them more flexible and drug-like. Synthetic endeavours within this class of compounds are broad and have led to the development of both remarkably potent and selective protein kinase inhibitors. Clinical BIM examples include ruboxistaurin and enzastaurin, which are highly active inhibitors of protein kinase C-β. While BIMs are widely recognised as protein kinase inhibitors, other modes of activity have been reported, including the inhibition of calcium signalling and antimicrobial activity. Critically, structural differences can be used to exploit new bioactivity and therefore it is imperative to discover new chemical entities to address new targets. BIMs can be highly functionalised or chemically manipulated, which provides the opportunity to generate new derivatives with unique biological profiles. This review will collate new synthetic approaches to BIM-type compounds and their associated bioactivities with a focus on clinical applications.

The synthesis of biologically active indolocarbazole natural products

Covering: up to 2020The indolocarbazoles, in particular indolo[2,3-a]pyrrolo[3,4-c]carbazole derivatives, are an important class of natural products that exhibit a wide range of biological activities. There has been a plethora of synthetic approaches to this family of natural products, leading to advances in chemical methodology, as well as affording access to molecular scaffolds central to protein kinase drug discovery programmes. In this review, we compile and summarise the synthetic approaches to the indolo[2,3-a]pyrrolo[3,4-c]carbazole derivatives, spanning the period from their isolation in 1980 up to 2020. The selected natural products include indolocarbazoles not functionalised at indolic nitrogen, pyranosylated indolocarbazoles, furanosylated indolocarbazoles and disaccharideindolocarbazoles.

Organic reactions in ionic liquids: N-alkylation of cyclic imides with alkyl halides promoted by potassium fluoride

An ionic liquid based on 1-butyl-3-methylimidazolium hexafluorophosphate is used as an efficient reusable reaction medium in the N-alkylation of cyclic imides with alkyl halides promoted by fluoride ion.

Chemistry and Properties of Indolocarbazoles

The indolocarbazoles are an important class of nitrogen heterocycles which has evolved significantly in recent years, with numerous studies focusing on their diverse biological effects, or targeting new materials with potential applications in organic electronics. This review aims at providing a broad survey of the chemistry and properties of indolocarbazoles from an interdisciplinary point of view, with particular emphasis on practical synthetic aspects, as well as certain topics which have not been previously accounted for in detail, such as the occurrence, formation, biological activities, and metabolism of indolo[3,2- b]carbazoles. The literature of the past decade forms the basis of the text, which is further supplemented with older key references.

A Unique Mdm2-Binding Mode of the 3-Pyrrolin-2-one- and 2-Furanone-Based Antagonists of the p53-Mdm2 Interaction

The p53 pathway is inactivated in almost all types of cancer by mutations in the p53 encoding gene or overexpression of the p53 negative regulators, Mdm2 and/or Mdmx. Restoration of the p53 function by inhibition of the p53-Mdm2/Mdmx interaction opens up a prospect for a nongenotoxic anticancer therapy. Here, we present the syntheses, activities, and crystal structures of two novel classes of Mdm2-p53 inhibitors that are based on the 3-pyrrolin-2-one and 2-furanone scaffolds. The structures of the complexes formed by these inhibitors and Mdm2 reveal the dimeric protein molecular organization that has not been observed in the small-molecule/Mdm2 complexes described until now. In particular, the 6-chloroindole group does not occupy the usual Trp-23 pocket of Mdm2 but instead is engaged in dimerization. This entirely unique binding mode of the compounds opens new possibilities for optimization of the Mdm2-p53 interaction inhibitors.

Design, synthesis and evaluation of 7-azaindazolyl-indolyl-maleimides as glycogen synthase kinase-3β (GSK-3β) inhibitors

A series of 7-azaindazolyl-indolyl-maleimides were designed, synthesized and evaluated for their GSK-3β inhibitory activity. Most compounds exhibited potent activity against GSK-3β. Among them, compounds 17a, 17b, 17g, 17i, 29a and 30 significantly reduced Aβ-induced Tau hyperphosphorylation, showin;g the inhibition of GSK-3β at the cell level. Preliminary structure-activity relationships were discussed based on the experimental data obtained.

Synthesis and biological evaluation of rebeccamycin analogues modified at the imide moiety

Glycosylated indolocarbazoles related to the antibiotic rebeccamycin represent an important class of antitumour drugs. In the course of our structure-activity relationship studies, new rebeccamycin analogues modified at the imide moiety were synthesised. The antiproliferative activity of the compounds was evaluated on three human cancer cell lines, A2780 (ovarian cancer), H460 (lung cancer), and GLC4 (small-cell lung cancer). The in vitro cytotoxicity of compounds 2 and 4, characterised respectively by a 1,3-dioxolan and (1,3-dioxolan-4-yl)methylene groups linked to the imide moiety, was higher than the reference compound, edotecarin. The effect of compound 2 in inducing tumour regression in the A2780 xenograft model was also investigated.

Synthesis of new azo compounds based on N-(4-hydroxypheneyl)maleimide and N-(4-methylpheneyl)maleimide

Maleic anhydride was reacted with p-aminophenol and p-toluidine in the presence of di-phosphorus pentoxide (P₂O₅) as a catalyst to produce two compounds: N-(4-hydroxy-phenyl)maleimide (I) and N-(4-methylphenyl)maleimide (II). The new azo compounds I(a-c) and II(a-c) were prepared by the reaction of I and II with three different aromatic amines, namely aniline, p-aminophenol and p-toluidine. The structures of these compounds were confirmed by CHN, FT-IR, ¹H-NMR, ¹³C-NMR, mass spectrum and UV/Vis spectroscopy.

Synthesis and biological evaluation of novel 4-azaindolyl-indolyl-maleimides as glycogen synthase kinase-3beta (GSK-3beta) inhibitors

A series of novel 4-azaindolyl-indolyl-maleimides were synthesized and evaluated for their GSK-3beta inhibitory activity. Most compounds exhibited high potency to GSK-3beta. Among them, compound 7c was the most promising GSK-3beta inhibitor. Preliminary structure-activity relationships were discussed based on the experimental data obtained and showed that different substituents on the indole ring and side chains at 1-position of indole had varying degrees of influence on the GSK-3beta inhibitory potency. In a cell-based functional assay, compounds 7c and 15a significantly reduced Abeta-induced Tau hyperphosphorylation by inhibiting GSK-3beta.

Efficient palladium-catalyzed synthesis of 3-aryl-4-indolylmaleimides

Improved palladium catalysts for the Suzuki coupling of 3-bromo-1-methyl-4-(2-methyl-3-indolyl)maleimide have been developed. The coupling of both aryl- and heteroarylboronic acids proceeds smoothly in good to excellent yields at low catalyst loading.

Synthesis, determination of stereochemistry, and evaluation of new bisindole alkaloids from the myxomycete Arcyria ferruginea: An approach for Wnt signal inhibitor

To determine the stereochemistry of dihydroarcyriarubin C (1), new bisindole alkaloid isolated from the myxomycete Arcyria ferruginea, cis- (2) and trans-dihydroarcyriarubin C (3) were synthesized. Comparison of their NMR characteristics allowed the trans stereochemistry of the natural product to be confirmed. Moreover, the Wnt signal inhibitory activities of 2 and 3 were compared with that of arcyriaflavin C (4), which is a natural product containing a bond between C-2 and C-2'. The cis-dihydroarcyriarubin C (2) showed moderate inhibition of Wnt signal transcription, which suggests that bisindole frameworks might be useful as small-molecule Wnt signal inhibitors.