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Stemona Alkaloids (stemona + alkaloid)
Selected AbstractsStrategies for the Synthesis of Stemona Alkaloids,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2009Ramon Alibés Abstract The extracts of several plants of the Stemonaceae family have long been used in Asian countries against differentdiseases and for their antiparasitic properties. Significant constituents of these extracts are a series of structurally related secondary metabolites named Stemona alkaloids. All the Stemona alkaloids are polycyclic and contain multiple stereocenters. Most of them present a central pyrrolo[1,2- a]azepine system and the majority also incorporate at least one ,-methyl-,-butyrolactone substructure. Their challenging molecular architectures have motivated the development of new strategies for the construction of their skeletons, but only a small number of total syntheses have been published and they are still limited to quite a small number of targets. This microreview briefly examines most of the synthetic approaches to these alkaloids, according to the strategies devised to assemble their intricate structures, stressing the main similarities and differences encountered in the work developed by different laboratories, as well as the variations introduced along the synthetic route when pursuing different alkaloids through a common strategy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Rapid structural determination of alkaloids in a crude extract of Stemona saxorum by high-performance liquid chromatography/electrospray ionization coupled with tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2009Shu-Ying Peng The electrospray ionization (ESI) mass spectrometric behavior of five Stemona alkaloids, stemokerrin, oxystemokerrin, oxystemokerrilactone, oxystemokerrin N -oxide and stemokerrin N -oxide, was studied using an ESI tandem mass technique (MSn). These compounds, isolated from Stemonasaxorum endemic in Vietnam, represent a class of alkaloids containing a pyrido[1,2-a]azepine A,B-ring core with a 1-hydroxypropyl side chain attached to C-4. Their fragmentation pathways were elucidated by ESI-MSn results and the elemental composition of the major product ions was confirmed by accurate mass measurement. In order to rationalize some fragmentation pathways, the relative Gibbs free energies of some product ions were estimated using the B3LYP/6-31+G(d) method. Based on the ESI-MSn results of five reference compounds, a reversed-phase high-performance liquid chromatography with tandem mass spectrometry (RP-HPLC/MSn) method was developed for the characterization of Stemona alkaloids with a pyrido[1,2-a]azepine A,B-ring core from the extract of S. saxorum. A total of 41 components were rapidly identified or tentatively characterized, of which 12 compounds were identified as Stemona alkaloids with a pyrido[1,2-a]azepine A,B-ring core, including four new compounds. This method is convenient and sensitive, especially for minor components in complex natural product extracts. Copyright © 2009 John Wiley & Sons, Ltd. [source] Novel Alkaloids from the Roots of Stemona sessilifoliaCHEMISTRY & BIODIVERSITY, Issue 3 2007Peng Wang Abstract Four new Stemona alkaloids, sessilistemonamines A,C (1,3, resp.) and dihydrostemoninine (4), were isolated from the roots of Stemona sessilifolia. Their structures and relative configurations were elucidated by means of in-depth 1D- and 2D-NMR-spectroscopic as well as mass-spectrometric experiments; and the structure of 4 was solved by X-ray single-crystal diffraction. The stereoisomeric compounds 1,3 share an unprecedented tetracyclic decahydro-1H -furo[2,,3,:4,5]cyclopenta[1,2- b]pyrrolo[1,2- a]azepine nucleus. Compounds 1 and 2 were found to be moderately active in terms of acetylcholinesterase (AchE) inhibition, with IC50 values of 68.8±9.5 and 17.1±2.5,,M, resp. [source] | ||||||||||