Absolute configuration of seco‐eudesmanolide inuloxin D from experimental and predicted chiroptical studies of its 4‐O‐acetyl derivative

Abstract

Sesquitepenoids inuloxins A–D, belonging to different subgroups, were isolated from Dittrichia viscosa and showed potential biocontrol of some parasitic plants as Pelipanche, Orobanche, and Cuscuta species. The absolute configurations of the first three inuloxins A–C were previously determined by using experimental and computational chiroptical spectroscopic methods. The absolute configuration of inuloxin D remains to be established. The bioactive inuloxin E, closely related to inuloxin D, was recently isolated from the same plant organic extract. The same relative configuration of inuloxin D was assigned to inuloxin E by comparison of their NMR spectroscopic data. The absolute configurations of inuloxin D and inuloxin E are suggested in this work by analysis of the experimental and predicted chiroptical properties of the 4‐O‐acetyl derivative of inuloxin D.

Chiroptical spectroscopic studies for the absolute configuration determination of hexahydrocurcumin and octahydrocurcumin

“…The magnitudes of predicted and experimental values for (+)‐( R , R )‐OHC differ significantly. Such significant differences between predicted and experimental ORD magnitudes were noted previously for other natural products 50–52 …”

“…Such significant differences between predicted and experimental ORD magnitudes were noted previously for other natural products. [50][51][52] Because ωB97X-D functional calculations better reproduced the experimental ECD spectrum of HHC, out of curiosity, we have also undertaken the ORD calculations for (R)-HHC with this functional. However, the ORD calculations with the ωB97X-D functional for (R)-HHC give magnitudes similar to those of experiment but with opposite signs (see Figure 11).…”