Pyrrolizidine spectroscopy

A Papua New Guinea sponge, Pseudoceratina sp., contains the unusual alkaloids ceratamines A (1142) and B (1143), and a biogenesis involving histidine and tyrosine is proposed (1173). The fermentation broth from Aspergillus fischeri var. thermomutatus has yielded CJ-12662 (1144) and UK-88051 (1145) (1174). The former metabolite was confirmed by X-ray spectroscopy and partial synthesis. A marine-derived Streptomyces sp. produces the novel pyrrolizidine 5-chlorobohem-amine C (1146), which was shown not to be an isolation artifact (1175). The Chinese medicinal plant Huperzia serrata has furnished 2-chlorohyperzine E (1147) (1176). 

In contrast to the dialkylpyrrolidine theme that characterizes the venoms of many Solenopsis (Diplorhoptrum) species (6), that of 3. xenovenenum is distinctive in containing a pyrrolizidine as the sole alkaloid. and C NMR spectroscopy show... 

There are only two known, naturally occurring trihydric saturated pyrrolizidine bases. The relative stereochemistry of rosmarinecine (123) was determined by Warren and co-workers.78 For the other base, croalbinecine (124), the chirality at C-l, C-7, and C-8 was defined by Sawhney et al.19 by correlation with turneforcidine (113) as shown in Eq. (33). The location of the third hydroxy group at C-2, indicated by NMR spectroscopy, was confirmed by decoupling experiments. It was further suggested by these workers79 that the configuration at C-2 is /i-hydroxy, on the basis of the... 

Pmr. Proton magnetic resonance (pmr) spectroscopy provides a reliable analysis of pyrrolizidine alkaloids if sufficient quantities of alkaloid 1 mg) are present The amount of total alkaloid is estimated by comparison of the area of the vinyl proton (H2) signal (present in all 1,2-unsaturated and seco alkaloids) with that of an added internal standard ( dinitrobenzene)... 

Ms. Mass spectroscopy has been used to characterize pyrrolizidine alkaloids since the mid 1960 s and the major fragmentation patterns have been determined (32-34). We have found that the rather low-intensity molecular ions observed in electron Impact (El) spectra can be dramatically enhanced by use of chemical ionization (isobutane) where intense ions corresponding to the molecular ion plus hydrogen are observed. The El and Cl spectra of lycopsamine shown in Figure 8 illustrate this phenomenon. 

A large number of naturally occurring pyrrolizidine compounds are known, and the C spectroscopy of these compounds has been extensively reviewed <83H(20)863, 90Pli>. Typical chemical shifts for these types of alkaloids are around 137 ppm for C-1, 125 ppm for C-2, 60 ppm for C-3, 55 ppm for C-5, 25-35 ppm for C-6, and 75 ppm for C-7a. C-7 is often oxygenated with chemical shifts around 75 ppm, but some nonoxygenated derivatives have been reported with chemical shifts for C-7 of around 30 ppm. 

Bicchi C, Rubiolo P, Frattini C (1989b) Capillary gas chromatography-Fourier transform infra-red spectroscopy of pyrrolizidine alkaloids of Senecio inaequidens DC. J Chromatogr 473 161-170... 

Pieters LA, Hartmann T, Janssens J, Vlietinck AJ (1989) Comparison of capillary gas chromatography with H an C nuclear magnetic resonance spectroscopy for the quantitation of pyrrolizidine alkaloids from Senecio vernalis. J Chromatogr 462 387-... 

Pyrrolizidine alkaloids poison animals grazing on toxic wild plants and those fed contaminated feed, causing economic losses. They poison humans through deliberate consumption of certain foods and herbal medicines and through consumption of food contaminated by wild plants, such as via transport of the toxins by bees into honey. Analytical methods are required for different purposes - to detect the presence of pyrrolizidine alkaloids, to quantify the total level of the toxins, or to measure the quantity of individual compounds. The task is made more challenging by the variety of PAs, their widespread nature and their different forms. Analytical methods are based on color reactions, enzyme linked immunosorbent assays (ELlSAs), spectroscopy, and the full range of chromatographic techniques. A lack of reference standards and... 

Segall HJ, Dallas JL (1983) H-l-NMR spectroscopy of pyrrolizidine alkaloids. Phytochemistry 22 1271-1273... 

Molyneux RJ, Johnson AE, Boitman JN, Benson ME 1979 Chemistry of toxic range plants. Determination of pyrrolizidine alkaloid content and composition in Senecio species by nuclear magnetic resonance spectroscopy. J Agr Food Chem 27 494... 

Gas liquid chromatography — mass spectrometry of silylated derivatives is a very sensitive method for detection of pyrrolizidine alkaloids 111). The many alkaloids containing retronecine (18) can be readily determined either by H n.m.r. spectroscopy utilising the downfield signal for the vinyl proton 211) or by gas liquid chromatography of fluorinated retronecine derivatives 101). 

Gupta, V. P., S. K. Handoo, and R. S. Sawhney Experimental Analysis of Ultraviolet Spectra of Some Pyrrolizidine Esters. Indian J. Pure Appl. Phys. 13, 776 (1975) SiMANEK, V., A. Klasek, and F. Santav Ultraviolet Absorption Spectroscopy of Some Pyrrolizidine Alkaloids. Collect. Czech. Chem. Commun. 34, 1832 (1969). 

Molyneux, R. j., a. E. Johnson, J. N. Roitman, and M. E. Benson Chemistry of Toxic Range Plants. Determination of Pyrrolizidine Alkaloid Content and Composition in Senecio species by Nuclear Magnetic Resonance Spectroscopy. J. Agric. Food Chem. 27, 494 (1979). 

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