Bisquinolizidine alkaloid

Bisquinolizidine alkaloids have also been widely studied by this technique. For instance, the crystal structure of (—)-A16(17 ,-dehydrolupaninium perchlorate 23 was obtained from sealed-tube and synchroton X-ray diffraction data, and showed that the A, B, C, and D rings assume distorted half-chair, chair, distorted sofa, and chair conformations, respectively it was also used to determine the most precise dimensions so far known for the iminium group <1999JST245>. The crystal structure of quinolizinium hexafluorophosphate has also been studied <2001CSC174>. 

The bisquinolizidine alkaloid petrosine, C30H50N2O2, was isolated from Pe-trosia seriata 112). IR absorption bands occur at 1712 (—CO—), 2770, and 2810 cm (trans-quinolizidine) protons of a secondary methyl group are at 8 0.94 J = 6.4 Hz) in the H-NMR spectrum. Examination of C-NMR and H-NMR spectra as well as X-ray structural analysis revealed the presence of two quinolizidine fragments in the petrosine molecule (65). They are joined by pen-... 

A new method for the quantitative determination of the conformational equilibrium of bisquinolizidine alkaloids in solution, by H and NMR, was developed by Wysocka and Brukwicki [199]. Using sparteine and 5,6-dehydromultiflorine. Fig. (30), as model compounds for a C ring in boat and chair conformation, respectively, the authors showed that the percentage of conformers with the C ring in boat conformation can be determined on the basis of the experimental chemical shifts of C-12 and C-14 and of the J coupling value of H-7/H-17P, by the formula Fb = (5-6c) /(6b-6c), where 5 is the experimentel value, and 5b and 5c represent the 5 or J coupling values of the model compoimds in boat and chair conformation, respectively. 

Fig. (30). Bisquinolizidine alkaloid 5,6-dehydromultifIurine with C ring in chair conformation [199]...

Some plants accumulate alkaloids with very different chemical structures which are nevertheless related biosynthetically. In some cases the biosynthetic route may be branched, but in some it is rather clear that the more complicated structures arise from the simpler molecules. The latter condition is encountered in lupines. While the majority of alkaloids are of a coupled quinolizidine structure, two uncommon alkaloids, lupinine and epilupinine, are of a simple quinolizidine structure. The idea that lupinine is a precursor of sparteine, i.e., a bisquinolizidine, was first proven by experiments in which radioactive lupinine was fed to the plants and radioactive sparteine and its derivatives were isolated (Schuette, 1960 Nowacki et al.y 1961). In this study, varieties of Lupinus luteus from Palestine, Portugal, and central Europe were tested. There were plants that produced only one major alkaloid, either sparteine or lupinine however, the hybrid plants which produced sparteine also produced a small amount of lupinine. Consequently, it was a typical example of intermediate inheritance. The F2... 

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