China
Africa
Explore chapters and articles related to this topic
Catalytic Asymmetric Friedel–Crafts Reactions of Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
The asymmetric Friedel–Crafts alkylation of indoles with nitroalkenes has gained substantial importance owing to the synthetic utility and versatility of chiral indole scaffolds in the frameworks of diverse biologically active indole alkaloids. Over the last two decades, substantial contributions have been made for this reaction by the development of several efficient catalytic systems. For instance, bifunctional hydrogen-bond donor organocatalysts and metal-based catalysts provided dual activation of the nitro group and the indole NH moiety. In 2008, the Jørgensen group reviewed asymmetric Friedel–Crafts alkylation catalyzed by copper.1 Later, Dalpozzo and co-workers published two review articles in 20102 and 20153 and highlighted the asymmetric functionalization of indoles, where few of the asymmetric Friedel–Crafts reactions of indole with nitroalkenes were discussed.4–18 Thus, to avoid overlap, here we try to focus more on the uncovered literature.
N-Polyheterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
Fischer indole synthesis has received considerable interest because a number of biologically interesting natural products contains highly functionalized indole skeletons [193–194]. A large number of indole alkaloids and their structural analogues are synthesized by microwave-assisted Fischer indole synthesis as a key step. Franco and Palermo [195] reported a microwave-assisted synthesis of iso-meridianins using ZnCl2-promoted microwave-assisted Fischer indole synthesis as the key step (Scheme 65). Iso-meridianins are close structural analogues of the naturally occurring indole alkaloids. Psammopemmins and Meridianins exhibit high anti-tumor activity as well [196–197]. Iso-meridianins contain a pyrimidine ring at the C-2 position of the indole, as against their parent compounds possessing a pyrimidine ring at the C-3 position. Phenylhydrazines and 2-aminopyrimidines are more easily available and considerably cheaper than functionalized indoles, therefore diversity-oriented and flexible synthesis can be achieved. The synthesis starts from commercially available isocytosine which is transformed into N-Boc-4-chloro analogue. Methyl ketone moiety is incorporated at the C-4 position through palladium-catalyzed cross-coupling of chloro derivative with tri-n-butyl(1-ethoxyvinyl)tin, followed by an acidic hydrolysis of the intermediate. The phenylhydrazones of compounds are then synthesized following standard methods [198a–b].
Thin-Layer Chromatography in Plant Sciences
Published in Bernard Fried, Joseph Sherma, Practical Thin-Layer Chromatography, 2017
Catharanthus. Indole alkaloids of Catharanthus roseus have been studied recently in plant tissues. Catharanthine, vindoline, leurosine, and vinblastine have been studied on silica gel with ethyl acetate–ethanol–benzene–ammonia (100:5:5:3).17 Quantitative analysis of serpentine and ajmalicine has been done on silica gel with chloroform–methanol (9:1) with detection by spraying with Dragendorff’s reagent followed by spraying with 10% sodium nitrite and scanning after 24 h at 435 nm.18 Two-dimensional TLC of indole alkaloids on silica gel has been studied with ethyl acetate–methanol (4:1) and dichloromethane–methanol (12:1)19 as mobile phases.
Evaluating the status of phytochemicals within Catharanthus roseus due to higher metal stress
Published in International Journal of Phytoremediation, 2021
V. Soumya, A. Sowjanya, P. Kiranmayi
Catharanthus roseus (L.) G. Don (also Vinca rosea L., Apocynaceae), an aboriginal perennial plant species of Madagascar, is often known as the Madagascar periwinkle. It is a popular ornamental plant which has currently acquired an equatorial distribution (Filippini et al.2003). Catharanthus roseus produces several monoterpenoids indole alkaloids (TIA) in different organs of the plants (Barnett et al.1978). Being a vital medicinal source (Ajaib et al.2010) of different alkaloid compounds, it is regarded as significant industrial crop. The plant procures its economic importance from its valuable leaf and root alkaloids that are antineoplastic and antihypertensive respectively. Phenolics are yet another class of plant metabolites that help in shielding the plant against abiotic and biotic stress. Several plant-derived drugs based on phenolic compounds show implications in neurodegenerative and cardiac diseases due to their antioxidant activity (Ferreres et al.2008). Plant phenolics include various categories of compounds like flavonoids, lignins, stilbenes, tannins and coumarins. However, Catharanthus roseus exhibits low levels of alkaloid and phenolic content in its parts making the isolation process costly. Due to exorbitant price of the isolated compounds, this plant has drawn considerable attention of the investigators (Moreno et al.1995, van der Heijden et al.2004). Biotechnological methods like semi- synthesis of compounds, cell and tissue culture are being considered as alternative sources of producing these phytoconstituents (Verpoorte et al.1997). However, most of the investigations showed only low amounts of desired products (Verpoorte et al.1999).