Stereochemical and NMR computational study of some natural dimeric bisindole alkaloids

The initial conformational search followed by the optimization of geometric parameters and high-level calculation of H-1 and C-13 NMR chemical shifts were carried out for 12 bisindole alkaloids of the Corynanthe-Strychnos series. Configurational assignments of all compounds from this series were performed based on the correlation of calculated and experimental NMR chemical shifts. For some alkaloids, the reassignment of the individual resonances together with spectral assignment of experimentally unresolved signals were suggested.