13C NMR and 1H lanthanide induced shifts of naturally occurring alkamides with cyclic amide moieties -amides from falcata

The 13C NMR spectra of 12 alkamides, especially of piperidides and piperideides isolated from different Achillea species were recorded. Assignments were based on systematic comparisons within the series of spectra and on selective 13C-{1H} decoupling experiments. Due to the dynamic behaviour of α, β-unsaturated 5- and 6-ring amides some carbon atoms of the cyclic amine moiety and the acid rest give rise to rather broad signals. Complementary information on the conformation of the amide bond and the geometry of the acid chain was obtained by means of 1h-lanthanide induced shifts (LIS). A re-investigation of the roots of Achillea falcata afforded in addition to known olefinic C10-carbonic acid amides a further new derivative of that series, 2E,4E, 8Z-deca-2,4,8-trienoic acid piperideide, together with three known acetylenic C11-carbonic acid amides, all derived from 2E,4E-undeca-2,4-diene-8,10-diynoic acid.