Cassane diterpenoids from the roots of Caesalpinia decapetala var. japonica and structure revision of caesaljapin.

Two cassane-type furanoditerpenoids, designated caesalacetal and caesalpinetate, and a norditerpenoid designated caesalpinone were isolated from the roots of Caesalpinia decapetala var. japonica along with seven known diterpenoids. Structures were elucidated by interpretation of their spectroscopic data, and the absolute structure of caesalacetal was confirmed by X-ray crystallographic analysis. Furthermore, the structure of a previously reported furanoditerpenoid, caesaljapin, was revised as its C-4 epimer on the basis of detailed NMR spectroscopic data as well as X-ray crystallographic analysis.