Studies on the Constituents of Scutellaria Species. XVIII. Structures of Neoclerodane-Type Diterpenoids from the Whole Herb of Scutellaria rivularis WALL.

Five neoclerodane-type diterpenoid lactones, scuterivulactones A, B, C1, C2 and D, have been isolated (scuterivulactone C2 was separated as the acetate) from the whole herb of Scutellaria rivularis WALL. (Labiaceae), and their structures have been determined based on chemical and physicochemical evidence as follows : scuterivulactone A, (4S, 11S)-11-acetoxy-6α-benzoyloxy-3, 4-epoxy-8β-hydroxy-13(14)-neocleroden-15, 16-olide; scuterivulactone B, (4R, 13R)-11β-acetoxy-6α-benzoyloxy-8β, 13-epoxy-3-oxo-15, 16-neoclerodanolide; scuterivulactone C1, (4R, 13R)-11β-acetoxy-6α-benzoyloxy-3α, 4β-dihydroxy-8β, 13-epoxy-15, 16-neoclerodanolide; scuterivulactone C2, (4R*, 13S*)-11β-acetoxy-6α-benzoyloxy-3α, 4β-dihydroxy-8β, 13-epoxy-15, 16-neoclerodanolide; and scuterivulactone D, (4R)-6α-benzoyloxy-3α, 4β-dihydroxy-11, 13(14)-neoclerodadien-15, 16-olide.