Simple indole alkaloids and those with a nonrearranged monoterpenoid unit
TL;DR: This review covers the literature on simple indole alkaloid and those with a nonrearranged monoterpenoid unit and newly isolated alkaloids, structure determinations, total syntheses and biological activities.
About: This article is published in Natural Product Reports.The article was published on 2005-11-25. It has received 531 citations till now.
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TL;DR: This review covers the literature published in 2014 for marine natural products, with 1116 citations referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms.
4,649 citations
TL;DR: This review focused on the recent development of indole derivatives as antiviral agents and summarized the structure property, hoping to inspire new and even more creative approaches to discover novel drugs with different modes of action.
575 citations
501 citations
TL;DR: An efficient synthesis of functionalized indoles from commercially available anilines by palladiumcatalyzed, intramolecular oxidative coupling is reported, with the ability to vary the aniline moiety so broadly is a distinct advantage of this new indole synthesis.
Abstract: The indole unit is one of the most abundant and relevant heterocycles in natural products and pharmaceuticals. Despite the existence of numerous methods for the synthesis and derivatization of indoles, the development of new, more efficient methods is of great importance. In this context, direct oxidative C C coupling by the selective activation of two C H bonds is a promising synthetic strategy. In contrast to established cross-coupling methods, such as the Suzuki– Miyaura coupling, prefunctionalization of the reaction centers is not required. For example, electron-rich aniline substrates can be activated and functionalized by electrophilic aromatic palladation under acidic conditions to give indolequinones or carbazoles. However, the limited scope of these reactions, the frequent requirement of a stoichiometric amount of a palladium complex, and the low yields often observed limit the usefulness of these methods. Furthermore, simple non-annulated indoles could not be prepared under these acidic conditions. Herein, we report an efficient synthesis of functionalized indoles from commercially available anilines by palladiumcatalyzed, intramolecular oxidative coupling. As this cyclization does not proceed through electrophilic aromatic palladation, a large variety of anilines can be used in this reaction. Our investigation commenced with the cyclization of methyl (Z)-3-(phenylamino)but-2-enoate (1a) to give the corresponding indole 2a. In experiments to optimize the reaction, the best results were obtained with a catalytic amount of Pd(OAc)2, Cu(OAc)2 as the oxidant, and K2CO3 as the base in DMF (Table 1, entry 1). Under these conditions, conversion was complete within 3 h at 80 8C (72% yield of the isolated product), or within less than 15 min at 140 8C, even when only 5 mol% of Pd(OAc)2 was used (not shown). Variation of the oxidant (Table 1, entries 3–6), the base (Table 1, entries 7 and 8), or the solvent (Table 1, entries 9–11) led to a decrease in the yield. The use of acetic acid as the solvent resulted in the rapid decomposition of the substrate and therefore no product formation (Table 1, entry 11). The results with Pd(TFA)2 (TFA= trifluoroacetate) were similar to those observed under the optimal conditions (Table 1, entry 12), whereas the addition of PPh3 resulted in the formation of a less active catalyst (Table 1, entry 13). Interestingly, chloride anions do not influence the reaction at all (Table 1, entry 14). A great variety of substituted anilines can be transformed into the corresponding indoles under the optimized reaction conditions (Table 2). In some cases, an increased reaction temperature (and, consequently, a shorter reaction time) led to higher yields. Substrates with a variety of electron-donating (Table 2, entries 2–8) and electron-withdrawing substituents (Table 2, entries 9–19) were converted directly into the indole products, which are versatile building blocks for subsequent synthetic modification, for example, through modern crosscoupling reactions (Table 2, entries 12–14). The ability to vary the aniline moiety so broadly is a distinct advantage of this new indole synthesis. In the case of meta-substituted substrates 1, two regioisomeric indole products 2 can be formed. Intriguingly, exclusive Table 1: Optimization of the reaction conditions.
385 citations
TL;DR: The focus of this Highlight is primarily on the construction of pyrrole rings during secondary metabolite formation, and on their derivatization and incorporation into natural products.
384 citations
References
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TL;DR: This review covers the isolation, structure determination, synthesis and biological activity of quinoline, quinazoline and acridone alkaloids from plant, microbial and animal sources.
1,687 citations
TL;DR: Specific biological activities of indole alkaloids presented here include: cytotoxicity, antiviral, antiparasitic, anti-inflammatory, serotonin antagonism, Ca-releasing, calmodulin antagonism and other pharmacological activities.
366 citations
351 citations
TL;DR: Okara fermented with Actinomucor elegans, Aspergillus oryzae, Neurospora intermedia, and Rhizopus oligosporus reduces cholesterol level and contains substances that counteract dietary free radicals.
Abstract: Large quantities of okara produced annually pose a significant disposal problem. It contains mostly crude fiber composed of cellulose, hemicellulose, and lignin, about 25% protein, 10-15% oil, but little starch or simple carbohydrates. It is a suitable dietary additive in biscuits and snacks because it reduces calorie intake and increases dietary fiber. The high-quality protein fraction has good water holding and emulsifying qualities and contains a peptide with anti-hypertension effects. The pectic polysaccharides fraction is suitable for thickening acid milk products. Okara fermented with Actinomucor elegans (meitauza), Aspergillus oryzae (koji), Neurospora intermedia (ontjom), and Rhizopus oligosporus (tempe), on consumption, reduces cholesterol level and contains substances that counteract dietary free radicals. Unique and useful products produced by Bacillus subtilis and Penicillium simplicissimum on okara include surfactin and iturin A (fungicidal), okaramines A, B, D-F (D is insecticidal), an oleanane triterpene, and two dihydroquinolinones (one toxic for Artemia salina). Okara has been used as silkworm food and in the production of ceramics.
302 citations
291 citations