A facile synthesis of deaza-analogues of the bisindole marine alkaloid topsentin

Base-Mediated Intramolecular Cyclization of α-Nitroethylallenic Esters as a Synthetic Route to 5-Hydroxy-3-pyrrolin-2-ones

An unprecedented Cs₂CO₃-mediated intramolecular cyclization/rearrangement cascade that transforms α-nitroethylallenic esters to functionalized pyrrolin-2-ones has been uncovered. This reaction provides a new and practical approach for the synthesis of medicinally privileged 5-hydroxy-3-pyrrolin-2-ones under mild conditions. The broad potential of this new method was demonstrated by an efficient Au/Ag-catalyzed heteroarylation of 5-hydroxy-3-pyrrolin-2-ones employing electron-rich heteroarenes to furnish heteroaryl-lactam derivatives.

Anticancer activity of bisindole alkaloids derived from natural sources and synthetic bisindole hybrids

The bisindole moiety, as a versatile pharmacophore, is one of the widespread heterocycles in naturally occurring and synthetic bioactive compounds. The bisindole alkaloids derived from natural sources possess structural and mechanistic diversity, and they were found to be generally more active than monoindole alkaloids against various cancer cell lines. Moreover, some bisindole alkaloids such as the tubulin inhibitors, vinorelbine and vinblastine, have already been approved for cancer therapy, suggesting that bisindole alkaloids are a significant source of anticancer agents and lead hits. Bisindole hybrids have the potential to overcome drug resistance, enhance efficiency, and reduce severe side effects. The bisindole-lactam hybrid midostaurin has already been approved for the treatment of adult patients with newly diagnosed acute myeloid leukemia who are FLT3 mutation-positive, highlighting the importance of bisindole hybrids in the development of novel anticancer agents. In this review, we present a brief account of the bisindole alkaloids derived from nature and of synthetic hybrids with potential anticancer activity developed in the recent 10 years.

Nanocrystalline ZnO: A Competent and Reusable Catalyst for the Preparation of Pharmacology Relevant Heterocycles in the Aqueous Medium

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Nanoparticle catalyzed synthesis is a green and convenient method to achieve most of the chemical transformations in water or other green solvents. Nanoparticle ensures an easy isolation process of catalyst as well as products from the reaction mixture avoiding the hectic work up procedure. Zinc oxide is a biocompatible, environmentally benign and economically viable nanocatalyst with effectivity comparable to the other metal nanocatalyst employed in several reaction strategies. This review mainly focuses on the recent applications of zinc oxide in the synthesis of biologically important heterocyclic molecules under sustainable reaction conditions.

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Application of zinc oxide in organic synthesis: Considering the achievable advantages of this nanocatalyst, presently several research groups are paying attention in anchoring zincoxide or its modified structure in several types of organic conversions e.g. multicomponent reactions, ligand-free coupling reactions, cycloaddition reaction, etc. The advantages and limitations of this nanocatalyst are also demonstrated. The present study aims to highlight the recent multifaceted applications of ZnO towards the synthesis of diverse heterocyclic motifs. Being a promising biocompatible nanoparticle, this catalyst has an important contribution in the fields of synthetic chemistry and medicinal chemistry.

Design and synthesis of newer 1,3,4-oxadiazole and 1,2,4-triazole based Topsentin analogues as anti-proliferative agent targeting tubulin

A set of two series of 1,3,4-oxadiazole (11a-n) and 1,2,4-Triazole (12a, c, e, g, h, j-n) based topsentin analogues were prepared by replacing imizadole moiety of topsentin through a multistep synthesis starting from indole. All the compounds synthesized were submitted for single dose (10 µM) screening against a NCI panel of 60-human cancer cell lines. Among all cancer cell lines, colon (HCC-2998) and Breast (MCF-7, T-47D) cancer cell lines were found to be more susceptible for this class of compounds. Among the compounds tested, compounds 11a, 11d, 11f, 12e and 12h, were exhibited good anti-proliferative activity against various cancer cell lines. Compounds 11d, 12e and 12h demonstrated better activity with IC₅₀ 2.42 µM, 3.06 µM, and 3.30 µM respectively against MCF-7 human cancer cell line than that of the standard drug doxorubicin IC₅₀ 6.31 µM. Furthermore, 11d induced cell cycle arrest at G0/G1 phase and also disrupted mitochondrial membrane potential with reducing cell migration potential of MCF-7 cells in dose dependent manner. In vitro microtubule polymerization assays found that compound 11d disrupt tubulin dynamics by inhibiting tubulin polymerization with IC₅₀ 3.89 μM compared with standard nocodazole (IC₅₀ 2.49 μM). In silico docking studies represented that 11d was binding at colchicine binding site of β-tubulin. Compound 11d emerged as lead molecule from the library of compounds tested and this may serve as a template for further drug discovery.

Recent Advances in the Chemistry of Conjugated Nitrosoalkenes and Azoalkenes

This review aims to present the most recent contributions in the chemistry of nitrosoalkenes and azoalkenes, highlighting the chemical behavior that makes them important and versatile building blocks in organic synthesis. These are heterodienes used in the assembly of a variety of heterocyclic systems, spanning from five- to seven-membered heterocycles, as well as for the functionalization of heterocycles.

Muscarine, imidazole, oxazole and thiazole alkaloids

Covering: July 2012 to June 2015. Previous review: Nat. Prod. Rep., 2013, 30, 869-915The structurally diverse imidazole-, oxazole-, and thiazole-containing secondary metabolites are widely distributed in terrestrial and marine environments, and exhibit extensive pharmacological activities. In this review the latest progress involving the isolation, biological activities, and chemical and biogenetic synthesis studies on these natural products has been summarized.

Anticancer properties of lamellarins

In 1985 the first lamellarins were isolated from a small oceanic sea snail. Today, more than 50 lamellarins have been inventoried and numerous derivatives synthesized and tested as antiviral or anticancer agents. The lead compound in the family is lamellarin D, characterized as a potent inhibitor of both nuclear and mitochondrial topoisomerase I but also capable of directly interfering with mitochondria to trigger cancer cell death. The pharmacology and chemistry of lamellarins are discussed here and the mechanistic portrait of lamellarin D is detailed. Lamellarins frequently serve as a starting point in the design of anticancer compounds. Extensive efforts have been devoted to create novel structures as well as to improve synthetic methods, leading to lamellarins and related pyrrole-derived marine alkaloids.

Microwave assisted synthesis of bis and tris(ω-bromoacetophenones): versatile precursors for novel bis(imidazo[1,2-a]pyridines), bis(imidazo[1,2-a]pyrimidines) and their tris-analogs

Background

α-Bromination of the side chain of aromatic ketones using NBS in the presence of p-toluenesulfonic acid (p-TsOH) in acetonitrile is very common. However, regioselective bromination of bis and tris(ω-bromoacetophenones) with NBS in the presence of p-TsOH in acetonitrile under microwave irradiation is quite novel. The bis- and tris(ω-bromoacetophenones) are used in synthesis of bis and tris(heterocycles). bis(heterocycles) have received a great deal of attention, because many biologically active natural and synthetic products have molecular symmetry. The use of the pressurized microwave irradiation is very advantageous to many syntheses and provide a large rate enhancement.

Results

Bis and tris(ω-bromoacetophenones) were obtained as single monobrominated derivatives in a shorter time than the conventional conditions. The results clearly demonstrate the better reactivity and selectivity of NBS/p-TsOH/CH₃CN as a brominating mixture under microwave conditions. The reaction of bis and tris(ω-bromoacetophenone) with 2-aminopyridine and 2-aminopyrimidine proceeded smoothly in a mixture of anhydrous ethanol and DMF under reflux or using 300 W/105°C/ 20 min microwave irradiation conditions to afford the corresponding bis(imidazo[1,2-a]pyridine), bis(imidazo[1,2-a]pyrimidine) and tris(imidazo[1,2-a]pyridine) derivatives in moderate to excellent yields. The carbonyl analogue of the targeted bis(imidazopyridines) could be synthesized by the reaction of N,N-dimethyl-N'-(pyridin-2-yl)formimidamide with bis(ω-bromoacetophenone) in refluxing ethanol. The structures of the newly synthesized compounds were confirmed by their spectral data as well as their elemental analyses.

Conclusion

In conclusion, selective α-bromination of bis- and tris(acetophenones) has been accomplished efficiently utilizing NBS/p-TsOH/CH₃CN under microwave irradiation. In addition, a facile synthesis of novel series of bis- and tris(imidazopyridine) and bis(imidazopyrimidine) derivatives.