HETERONUCLEAR NMR-STUDIES OF THE CHROMONE ALKALOIDS AND REVISION OF THE STRUCTURE OF SOME PIPERIDINO-CHROMONE ALKALOIDS

The C-13-NMR spectra of seven chromone alkaloids isolated from Schuman niophyton magnificum have been obtained. Assignment of signals was car ried out with the help of heteronuclear coupling experiments and other correlation techniques on the alkaloids an their acyl derivatives. On the basis of the signals observed the structures of the piperidino-al kaloid schumannificine and its N-methyl and anhydro analogues have bee n revised to that of a piperidone right linked to the noreugenin via a carbon-carbon bond and a lactol bridge.