Nudicaulins, yellow flower pigments of papaver nudicaule: Revised constitution and assignment of absolute configuration

Article abstract of DOI:10.1021/ol303211w

The constitution of the aglycon of nudicaulin has been revised to be a pentacyclic indole alkaloid. The relative and absolute configurations of the two diastereomers, nudicaulins I (3a) and II (3b), have been assigned by NMR, conformational analyses, and interpretation of the experimental ECD spectra by quantum-chemical calculations.