Scutebarbatines W-Z, new neo-clerodane diterpenoids from Scutellaria barbata and structure revision of a series of 13-spiro neo-clerodanes

Four new neo-clerodane Diterpenoids, scutebarbatines W-Z (1-4), were isolated from the ethanol extract of Scutellaria barbata (Labiatae), and their structures were elucidated on the basis of extensive spectroscopic studies. In addition, the proposed structures of at least seven 13-spiro subtype neo-clerodanes: scutehenanine B (5), scutebarbatine G (6), 6-O-nicotinoylscutebarbatine G (7), barbatin A (8), 6,7-di-O-nicotinoylscutebarbatine G (9), 6-O-nicotinoyl-7-O-acetylscutebarbatine G (10), and scutebarbatine F (11), reported by Dai and co-workers from the same species, were incorrectly assigned and have been revised by reanalysis of the published NMR data.