FURTHER-STUDIES ON THE STEREOCHEMISTRY OF SPARTEINE, ITS ISOMERS AND DERIVATIVES .22. C-13 NMR ANALYSIS OF SPARTEINE DERIVATIVES SUBSTITUTED IN EXTERNAL RINGS - MONOSALTS

The C-13 NMR spectra of six sparteine derivatives were analysed. In fo ur of them, the substituent phenyl, methyl or cyano was in the externa l A ring of the molecule at C(2), while in the other two, the substitu ent was attached to C(15) in ring D. The analysis was based on a compa rison of the spectra of the studied monocations with the spectra of th e sparteine monocation taken under the same conditions, including the off-resonance spectra. This work was aimed at determining the characte r of the changes in the chemical shift (substituent and protonation ef fects), to provide a greater insight into the configurational-conforma tional changes of the sparteine skeleton in CD3CN solution. All the an alysed derivatives adopt the all-chair trans-A/B: cis-C/D bis-quinoliz idine skeleton.