ent-kaurane diterpenoids from Annona glabra

Three new kaurane diterpenoids, annoglabasin C (16 alpha-acetoxy-ent-kauran -19-oic acid-17-methyl ester) (1), annoglabasin D (16 alpha-acetoxy-ent-kau ran-19-al-17-methyl ester) (2), and annoglabasin E (16 alpha-hydro-19-ol-en t-kauran-ol-17-oic acid) (3), and a new norkaurane diterpenoid, annoglabasi n F (16 alpha-acetoxy-19- nor-ent-kauran-4 alpha-ol-17-methyl ester) (4), a long with 13 known kaurane derivatives were is elated from the stems of Ann ona glabra. 16 alpha-Methoxy-ent-kauran-19-oic acid (5) and 16 alpha-hydro- ent-kauran-17,19-dimethyl ester (6) were obtained for the first time as nat ural products. The structures of compounds 1-6 were characterized by spectr al analysis.