A new catalytic method for the denitrogenative transannulation/cyclopropanation of in‐situ‐generated 2‐(diazomethyl)pyridines is described using a cobalt‐catalyzed radical‐activation mechanism. The ...method takes advantage of the inherent properties of a CoIII‐carbene radical intermediate and is the first report of denitrogenative transannulation/cyclopropanation by a radical‐activation mechanism, which is supported by various control experiments. The synthetic benefits of the metalloradical approach are showcased with a short total synthesis of (±)‐monomorine.
Denitrogenative transannulation/cyclopropanation of in‐situ‐generated 2‐(diazomethyl)pyridine is presented, which involves a cobalt‐catalyzed radical‐activation mechanism. A cobalt(II)‐metalloradical undergoes radical addition to alkynes during denitrogenative transannulation, or to alkenes during cyclopropanation, forming indolizines and cyclopropanes, respectively
A concept for intramolecular denitrogenative C(sp3)–H amination of 1,2,3,4-tetrazoles bearing unactivated primary, secondary, and tertiary C–H bonds is discovered. This catalytic amination follows ...an unprecedented metalloradical activation mechanism. The utility of the method is showcased with the short synthesis of a bioactive molecule. Moreover, an initial effort has been embarked on for the enantioselective C(sp3)–H amination through the catalyst design. Collectively, this study underlines the development of C(sp3)–H bond functionalization chemistry that should find wide application in the context of drug discovery and natural product synthesis.
An efficient strategy for the intramolecular denitrogenative transannulation/C(sp2)–H amination of 1,2,3,4-tetrazoles bearing C8-substituted arenes, heteroarenes, and alkenes is described. The ...process involves the generation of the metal–nitrene intermediate from tetrazole by the combination of Cp*IrCl22 and AgSbF6. It has been shown that the reaction proceeds via an unprecedented electrocyclization process. The method has been successfully applied for the synthesis of a diverse array of α-carbolines and 7-azaindoles.
A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4‐tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the ...traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates.
1,2,3,4: A unique intermolecular denitrogenative annulation of 1,2,3,4‐tetrazoles and alkynes was discovered by employing a catalytic amount of Fe(TPP)Cl and Zn dust. This reaction precludes the traditional click reaction between organic azides and alkynes.
A general catalytic method using a Mn‐porphyrin‐based catalytic system is reported that enables two different reactions (click reaction and denitrogenative annulation) and affords two different ...classes of nitrogen heterocycles, 1,5‐disubstituted 1,2,3‐triazoles (with a pyridyl motif) and 1,2,4‐triazolo‐pyridines. Mechanistic investigations suggest that although the click reaction likely proceeds through an ionic mechanism, which is different from the traditional click reaction, the denitrogenative annulation reaction likely proceeds via an electrophilic metallonitrene intermediate rather than a metalloradical intermediate. Collectively, this method is highly efficient and offers several advantages over other methods. For example, this method excludes a multi‐step synthesis of the N‐heterocyclic molecules described and produces only environmentally benign N2 gas a by‐product.
A Mn‐porphyrin‐based catalytic method that enables access to two different classes of nitrogen heterocycles is reported. Mechanistic investigations found that a 1,3‐cycloaddition click reaction occurs directly via the Mn‐bound complex, whereas denitrogenative annulation proceeds through an Mn‐N complex. The reported method is compatible with a wide range of substrates for both reactions.
A catalytic system for intermolecular benzylic C(sp3)–H amination is developed utilizing 1,2,3,4-tetrazole as a nitrene precursor via iron catalysis. This method enables direct installation of ...2-aminopyridine into the benzylic and heterobenzylic position. The method selectively aminates 2° benzylic C(sp3)–H bond over the 3° and 1° benzylic C(sp3)–H bonds. Experimental studies reveal that the C(sp3)–H amination undergoes via the formation of a benzylic radical intermediate. This study reports the discovery of new method for 2-pyridine substituted benzylamine synthesis using inexpensive, biocompatible base metal catalysis that should have wide application in the context of medicinal chemistry and drug discovery.
To fulfil its commitments towards sustainable development, India is transitioning from fossil fuels to renewables in the energy sector, trying to shift consumption and cropping practices in the ...agriculture sector, and promoting alternative fuel vehicles in the transport sector. In this study, we analyse the current state of energy, agriculture, and transport policies using the triple bottom line approach and provide a strategic framework that offers a mechanism and a long-term roadmap for a sustainable future by integrating the synergies between these three key sectors. Decentralised production and consumption of resources holds the key to economic, environmental, and social sustainability.
Several studies have shown that endophytic fungal metabolites possess vital biological activities; nevertheless, there is a lack of knowledge regarding the medicinally important marine endophytic ...fungi associated with the seaweeds mainly found in the Bay of Bengal, Bangladesh. In this study, six endophytic fungi, belonging to five genera and four classes, were isolated from the well-known chlorophyte,
sp. and were most closely related to
,
,
sp.,
,
and
sp. This is the first report of these fungi as endophytes associated with
sp. from the Bay of Bengal, Bangladesh. A preliminary biological evaluation of the ethyl acetate extract of each endophytic fungal crude extract was the prime objective of this research, e.g., antimicrobial assay, 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity and brine shrimp lethality bioassay. Evaluation of test results revealed that each fungal crude extract possessed one or more relevant biological activities. Preliminary chemical screening using TLC and NMR spectroscopic analysis revealed the presence of several secondary metabolites in the crude fungal extracts. These findings suggest that the marine endophytic fungus may be a valuable source for investigating potentially bioactive chemicals or leads for novel drug candidates.
Display omitted
•Endophytric fungi are natural reservoir for bioactive secondary metabolites.•Fusarium solani, an endophytic fungus, is a rich source for secondary metabolites specially for quinone ...groups.•Napthaquinone and aza-anthraquinone derivatives have significant antimicrobial, antioxidant and cytotoxic effect.•Napthaquinone and aza-anthraquinone derivatives have the potentiality to be lead for anticancer and antimicrobial agent.•Aza-anthraquinone derivatives are more bioactive than napthaquinone group due to the presence of nitrogen group.
This study reports the chemical investigation and bioactivity of the secondary metabolites produced by the endophytic fungus Fusarium solani isolated from Cassia alata Linn. growing in Bangladesh. This plant was collected from conservation forest in Bangladesh and belongs to the Caesalpiniaceae family. The endophytic fungus Fusarium solani was isolated from the tissue of root of this plant. The fungal strain was identified by morphological characters and DNA sequencing. The crude organic extract of the fungal strain was proven to be active when tested for cytotoxicity against Brine Shrimp Lethality Bioassay, antimicrobial and antioxidant activity. The bioactivity guided fractionation of the ethyl acetate extract leads to the isolation of seven secondary metabolites in pure form. The structures of the isolated compounds were determined by the analysis of NMR and mass spectroscopic data. Bioassay investigation of the isolated secondary metabolites suggested aza-anthraquinones are more potent bioactive compounds as anticancer and antimicrobial agent.
This study was conducted to isolate and identify the endophytic fungi from the bark and leaves of the Syzygum cumini plant and investigate the pharmacological activities of endophytic fungi along ...with plant parts. After isolation, endophytic fungi were identified based on morphological characteristics and molecular identification. Antimicrobial, antioxidant, and cytotoxic activities were studied by a disc diffusion method, free radical scavenging DPPH assay, and brine shrimp lethality bioassay, respectively. A total of eight endophytic fungi were isolated and identified up to the genus level based on morphological characteristics and confirmed by molecular identification techniques. Among the eight isolates, three isolates were identified as Colletotrichum sp. (SCBE-2, SCBE-7, and SCLE-9), while the rest of the isolates belonged to Diaporthe sp. (SCBE-1), Pestalotiopsis sp. (SCBE-3), Penicillium sp. (SCBE-4), Phyllosistica sp. (SCLE-7), and Fusarium sp. (SCLE-8). The presence of flavonoids, anthraquinones, coumarins, and isocoumarins was assumed by the preliminary screening of the fungal and plant extracts by a thin-layer chromatographic technique under UV light. Fungal extracts of Pestalotiopsis sp. Penicillium sp. were found sensitive to all test bacteria, but only extracts from the leaf and bark showed significant antifungal activity along with their antimicrobial activity. Penicillium sp. The fungal extract showed the highest free radical scavenging activity (2.43 μg/mL) near that of ascorbic acid (2.42 μg/mL). Some fungal extracts showed cytotoxic activity that, in general, suggests their probable abundance of biological metabolites. This is the first approach to investigate the endophytic fungi of Syzygium cumini Linn. in Bangladesh, to find the pharmacological potential of endophytes, and to explore novel compounds from those endophytes.
PDF
