Nuphar alkaloids spectroscopy

Nupharolidine (9) was isolated from Nuphar lutea (28). Its structure was determined by IR, 1H-NMR, and mass spectroscopy. Compound 9 was the first example of a Nuphar alkaloid with a hydroxyl group in the quinolizidine system. This alkaloid is isomeric with castoramine (59), nuphamine, and isocastora-mine (10). 

C-NMR spectrometry has assumed a very efficient role in the determination of the structure and stereochemistry of Nuphar alkaloids and their derivatives. Accurate assignments of chemical shift values to particular carbon atoms in the molecules and clear changes in chemical shift values of particular carbon atoms, owing to conformational transformations, are well within the rules generally accepted for I3C-NMR spectroscopy, which facilitates identification of the signals in the l3C-NMR spectra. 

N. luteum also yielded an unresolved mixture of 6-hydroxy- and 6 -hydroxy-neothiobinupharidine, (27) and (28), respectively, in a ratio of 23 79. The mixture, which gave a single product, neothiobinupharidine, when reduced with borohydrate, was analysed by n.m.r. and mass spectroscopy. The latter technique has proved particularly important for structural studies in this area and its application has been assisted by a useful study of the mass spectra of Nuphar alkaloids of the monomeric and thiospirane types. ... 

Valenta and Liu have given an account of the structure and synthesis of Ormosia alkaloids, and a review of the Nuphar alkaloids has been published. Carbon-13 n.m.r. and mass spectroscopy of quinoiizidine alkaloids have been reviewed. 

A new thiohemiaminal type of alkaloid was also isolated from Nuphar lutea (33), and its structure was determined by NMR spectroscopy and by NaBD4 reduction to thiobinupharidine-6 -d,. The new compound is thus 6 -epihydroxy-thiobinupharidine (22). 

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