Bio: Avijit Banerji is an academic researcher from University of Calcutta. The author has contributed to research in topic(s): Cycloaddition & Aryl. The author has an hindex of 16, co-authored 121 publication(s) receiving 911 citation(s).
TL;DR: Two more indolic bases, rhazinine and R1, were shown to be identical with antirhine and geissoschizine respectively and the biogenetic significance of the occurrence of the latter is discussed.
Abstract: Chemical investigation of Rhazya stricta Decaisne has led to the isolation of more than a dozen indole alkaloids. Two more indolic bases, rhazinine and R1, obtained from this plant, were shown to be identical with antirhine and geissoschizine respectively. The biogenetic significance of the occurrence of the latter is discussed. Four other minor indole alkaloids, viz. R2, R3, rhazinilam and rhazinaline are also present.
TL;DR: The bioassay guided fractionation of the n-hexane extract of the seeds of Murraya koenigii Spreng resulted in the isolation of three bioactive carbazole alkaloids, kurryam (I), koenimbine (II) and koenine (III).
Abstract: The bioassay guided fractionation of the n-hexane extract of the seeds of Murraya koenigii Spreng (Rutaceae) resulted in the isolation of three bioactive carbazole alkaloids, kurryam (I), koenimbine (II) and koenine (III). The structures of the compounds were confirmed from their 1H-, 13C-, and 2D-NMR spectral data. Of the three compounds (I) and (II) exhibited significant inhibitory activity against castor oil-induced diarrhoea and PGE2-induced enteropooling in rats. The compounds also produced a significant reduction in gastrointestinal motility in the charcoal meal test in Wister rats.
Abstract: Two new amides, aurantiamide and aurantiamide acetate, were isolated from Piper aurantiacum Their structures were determined as N-(N′-benzoyl-S-phenylalaninyl)-S-phenylalaninol and its acetate, respectively, from chemical and spectroscopic studies The structures and stereochemistry were confirmed by synthesis The corresponding diastereoisomers were also synthesized and their spectroscopic properties compared with those of the natural compounds
Abstract: Alstonia scholaris: The structure of the indole alkaloid nareline Besides the known akuammidine, picralinal, picrinine and pseudoakuammigine a new indole alkaloid called nareline (M=352) was isolated from Alstonia scholaris R. BR., which belongs to the plant family of Apocynaceae. Its structure 2 was deduced by single crystal X-ray diffraction. 2 represents the absolute configuration. The spectroscopic data of 2 and its derivatives (Scheme 1) as well as their chemical behavior support this structure. In biogenetic sense nareline is related to the bases akuammiline (4) and picraline (5) (Scheme 2). In contrast to those the C-atom 5 is exocyclic and represents an aldehyde group which forms together with the oxygen atom of the N (4)-hydroxylamine group a cyclic half acetale. - By oxidation (CrO3/CH3COOH) of 2 the oxindol derivative 19 (oxonareline) is formed which contains a cyclic acetal as a partial structure element (Scheme 4).
Abstract: Two new unsaturated amides, retrofractamides A and C, were isolated from the total above-ground parts of Piper retrofractum . Retrofractamide A was shown to be N -isobutyl-9(3′,4′-methylenedioxyphenyl)2 E ,4 E ,8 E -nonatrienamide from spectroscopic and chemical investigations. The structure 6 for retrofractamide C was suggested from spectroscopic and chemical studies and was confirmed by a total stereoselective synthesis. The presence of sesamin and 3,4,5-trimethoxydihydrocinnamic acid as well as two higher homologues of retrofractamide A, viz. pipericide (retrofractamide B) and retrofractamide D was demonstrated. The synthesis of pipericide was also achieved.
TL;DR: This tutorial review describes selected recent examples of how the metal-catalysed C-H bond functionalisation has been able to positively affect the synthesis of natural products.
Abstract: Metal-catalysed C–H bond functionalisation has had a significant impact on how chemists make molecules. Translating the methodological developments to their use in the assembly of complex natural products is an important challenge for the continued advancement of chemical synthesis. In this tutorial review, we describe selected recent examples of how the metal-catalysed C–H bond functionalisation has been able to positively affect the synthesis of natural products.
Abstract: The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed. Nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references. © 1997 Elsevier Science Ltd
TL;DR: This review describes the biochemistry of tubulin, microtubules, and the mitotic spindle and describes the natural and synthetic agents which are known to interact with tubulin.
Abstract: Tubulin is the biochemical target for several clinically used anticancer drugs, including paclitaxel and the vinca alkaloids vincristine and vinblastine. This review describes both the natural and synthetic agents which are known to interact with tubulin. Syntheses of the more complex agents are referenced and the potential clinical use of the compounds is discussed. This review describes the biochemistry of tubulin, microtubules, and the mitotic spindle. The agents are discussed in relation to the type of binding site on the protein with which they interact. These are the colchicine, vinca alkaloid, rhizoxin/maytansine, and tubulin sulfhydryl binding sites. Also included are the agents which either bind at other sites or unknown sites on tubulin. The literature is reviewed up to October 1997. © 1998 John Wiley & Sons, Inc., Med Res Rev, 18, No. 4, 259–296, 1998.
TL;DR: Recently completed total syntheses showcasing creative and ingenious incorporation of C-Hactivation as a strategic manoeuver are compared with their "non-C-H activation" counterparts, illuminating a new paradigm in strategic synthetic design.
Abstract: The recent advent of transition-metal mediated CH activation is revolutionizing the synthetic field and gradually infusing a “CH activation mind-set” in both students and practitioners of organic synthesis. As a powerful testament of this emerging synthetic tool, applications of CH activation in the context of total synthesis of complex natural products are beginning to blossom. Herein, recently completed total syntheses showcasing creative and ingenious incorporation of CH activation as a strategic manoeuver are compared with their “non-CH activation” counterparts, illuminating a new paradigm in strategic synthetic design.
Author's H-index: 16