Mass spectra of N-oxides of pyrrolizidine alkaloids

Summary The mass spectra of the N-oxides of pyrrolizidine alkaloids show three main types of ions formed as the result of the detachment of the oxygen of the NO group, dehydration with subsequent dehydrogenation, and isomerization of the nucleus. In a number of spectra the proportion of ions formed by the localization of the charge in the side chain increases.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 620–626, September–October, 1974.     

Macrocyclic bis-quinolizidine alkaloids from Xestospongia muta

A new stereoisomer Meso-araguspongine C together with nine reported macrocyclic bis-quinolizidine alkaloids araguspongines A, C, E, L, N?P, petrosin, and petrosin A were isolated from marine sponge Xestospongia muta. Stereochemistry of meso-araguspongine C (2) and araguspongines N-P (3?5) were established by their NMR data and conformational analyses. Both araguspongine C (1) and meso-araguspongine C (2) exhibited great cytotoxic activity towards HepG-2, HL-60, LU-1, MCF-7, and SK-Mel-2 human cancer cells (IC₅₀ in the range of 0.43–1.02 μM). At a concentration of 20 μM, isolated compounds (1?10) also showed modest inhibitory effects (from 7.6 to 40.8%) on the NO production in LPS activated RAW264.7 macrophages.     

Two new pyrrolizidine alkaloids from Senecio nemorensis

Two new compounds, including petasinoside A and chloridate-[N-chloromethyl-hectorine], were isolated from Senecio nemorensis. The structures of these compounds were elucidated by spectroscopic methods including 1D and 2D NMR experiments.     

Flexible strategy for the synthesis of pyrrolizidine alkaloids

A general strategy for the production of pyrrolizidine alkaloids is described, starting from intermediate (+)-9. The key features are diastereoselective dihydroxylation, inversion at the ring junction by hydroboration of an enamine, and ring closure to form the bicyclo ring system. This route is attractive because of its brevity and versatility; four natural products were prepared with differing stereochemistry and substitution patterns. Finally, this work allowed assignment of the absolute stereochemistry of 2,3,7-triepiaustraline and hyacinthacine A 7.     

Bisquaternary salts of pyrrolizidine alkaloids and their derivatives

Summary ,-Bisquaternary salts of the pyrrolizidine series have been synthesized by the reaction of ,-dibromoalkanes with some products of the cleavage of pyrrolizidine alkaloids (lindelofidine, hydroxyheliotridene, and their esters).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 77–80, January–February, 1977.     

Update on analytical methods for toxic pyrrolizidine alkaloids

Methods for the determination of toxic pyrrolizidine alkaloids in plants and foods are described with emphasis on the important aspects of sample extraction and clean-up and the now preferred determination by liquid chromatography–mass spectrometry. The efficiencies of different extraction solvents and methods are described, as are the methods of reduction of N-oxides. Appropriate liquid chromatography–mass spectrometry conditions are tabulated. This concise review is intended to guide analysts towards adopting a more unified and reliable approach to the analysis of these important toxins.     

Synthetic RCM approaches to enantiopure polyhydroxylated pyrrolizidine alkaloids

RCM approach to hindered 5-5-fused bicyclic pyrrolizidine system starting from chiral pyrrolidine, obtained from d-(+)-mannose, has been achieved in convenient yield.     

Three new pyrrolizidine alkaloids derivatives from Liparis nervosa

Three new pyrrolizidine alkaloids, nervosine VⅡ (1), nervosine VⅢ(2) and nervosine Ⅸ(3) were isolated from the whole plant extract of Liparis nervosa. Their structures were elucidated by extensive spectroscopic analyses(including 1D, 2D NMR, and HR-ESI-MS) and chemical methods. Compounds 1–3were evaluated for their cytotoxic activity against A549, MCF-7and H460 human cancer cell lines.     

Asymmetric and enantiospecific syntheses of 1-hydroxymethyl pyrrolizidine alkaloids

Isoretronecanol and trachelantamidine (laburnine) are naturally occurring pyrrolizidine alkaloids which display potent biological activity, and as such these compounds have, in recent years, attracted significant interest from the bioorganic and synthetic communities. This review delineates both the asymmetric and enantiospecific syntheses of 1-hydroxymethyl pyrrolizidine alkaloids including isoretronecanol, trachelantamidine (laburnine) and related hydroxylated compounds.     

Mass spectra and stereochemistry of some macrocyclic pyrrolizidine alkaloids

Conclusions On the basis of the results of a comparison of the mass spectra of macrocyclic pyrrolizidine alkaloids with a known configuration of the side chain (trichodesmine, monocrotaline) with the spectra of incanine, crispatine, and fulvine a hypothesis has been put forward on the relative positions of the substituents at C₂ and C₃ in the molecules of the three latter compounds.Order of the Red Banner of Labor Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 40–44, January–February, 1974.