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The 13C NMR spectra of the isomeric alkaloids lupinine and epilupinine and their perchlorates, methiodides and N-oxides are discussed. Chemical shift changes due to protonation, quaternizatiOn and N-oxidation are andysed. The trans-quinolizidine ring fusion is proved for epilupinine salts and for the N-oxide. hpinine also exists predominantly with the trans ring fusion, but the cis ring fusion is found in the methiodide. An equiliirium of two stereoisomers, one with tram-and the other with cis-ring fusion, has been established for lupinine perchlorate in D20 solution. Lupinine N-oxides isolated in the crystalline state are shown to have both trans-and the cis-ring fusion.

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