Carbon‐13 NMR spectral studies on some labdane diterpenoids

Abstract Carbon‐13 NMR signal assignments of the labdane diterpenoids andrographolide and 14‐deoxyandrographolide, along with their acetates, and isodeoxyandrographolide have been made. This study indicates that the C‐6 and C‐11 resonance assignments of isovirescenol‐B, made earlier, should be interchanged.