95462-15-0Relevant articles and documents
Semi-automated separation of the epimeric dehydropyrrolizidine alkaloids lycopsamine and intermedine: Preparation of their N-oxides and NMR comparison with diastereoisomeric rinderine and echinatine
Colegate, Steven M.,Gardner, Dale R.,Betz, Joseph M.,Panter, Kip E.
, p. 429 - 438 (2014/11/12)
Introduction The diversity of structure and, particularly, stereochemical variation of the dehydropyrrolizidine alkaloids can present challenges for analysis and the isolation of pure compounds for the preparation of analytical standards and for toxicology studies. Objective To investigate methods for the separation of gram-scale quantities of the epimeric dehydropyrrolizidine alkaloids lycopsamine and intermedine and to compare their NMR spectroscopic data with those of their heliotridine-based analogues echinatine and rinderine. Methods Lycopsamine and intermedine were extracted, predominantly as their N-oxides and along with their acetylated derivatives, from commercial samples of comfrey (Symphytum officinale) root. Alkaloid enrichment involved liquid-liquid partitioning of the crude methanol extract between dilute aqueous acid and n-butanol, reduction of N-oxides and subsequent continuous liquid-liquid extraction of free base alkaloids into CHCl3. The alkaloid-rich fraction was further subjected to semi-automated flash chromatography using boronated soda glass beads or boronated quartz sand. Results Boronated soda glass beads (or quartz sand) chromatography adapted to a Biotage Isolera Flash Chromatography System enabled large-scale separation (at least up to 1-2 g quantities) of lycopsamine and intermedine. The structures were confirmed using one- and two-dimensional 1H- and 13C-NMR spectroscopy. Examination of the NMR data for lycopsamine, intermedine and their heliotridine-based analogues echinatine and rinderine allowed for some amendments of literature data and provided useful comparisons for determining relative configurations in monoester dehydropyrrolizidine alkaloids. A similar NMR comparison of lycopsamine and intermedine with their N-oxides showed the effects of N-oxidation on some key chemical shifts. A levorotatory shift in specific rotation from +3.29° to -1.5° was observed for lycopsamine when dissolved in ethanol or methanol respectively. Conclusion A semi-automated flash chromatographic process using boronated soda glass beads was standardised and confirmed as a useful, larger scale preparative approach for separating the epimers lycopsamine and intermedine. The useful NMR correlations to stereochemical arrangements within this specific class of dehydropyrrolizidine alkaloid cannot be confidently extrapolated to other similar dehydropyrrolizidine alkaloids.
Synthesis of pyrrolizidine alkaloids indicine, intermedine, lycopsamine, and analogues and their N-oxides. Potential antitumor agents
Zalkow,Glinski,Gelbaum,Fleischmann,McGowan,Gordon
, p. 687 - 694 (2007/10/02)
(-)- and (+)-trachelanthic and (-)- and (+)-viridifloric acids were synthesized and their isopropylidene derivatives were regiospecifically coupled, at C-9, with (-)-retronecine (2) obtained by hydrolysis of monocrotaline (1), isolated from Crotalaria spectabilis. Hydrolysis, followed by oxidation, led to the N-oxides of indicine (7), intermedine (13), lycopsamine (15), and the new nonnatural product 16, respectively. Each of these analogues was screened in the P388 lymphocytic leukemia system at the same time as indicine N-oxide, and the results were compared. Other related analogues were prepared and similarly screened and the results compared with those from indicine N-oxide.
