ent-Kaurane Diterpenoids from Annona glabra

Abstract

Three new kaurane diterpenoids, annoglabasin C (16alpha-acetoxy-ent-kauran-19-oic acid-17-methyl ester) (1), annoglabasin D (16alpha-acetoxy-ent-kauran-19-al-17-methyl ester) (2), and annoglabasin E (16alpha-hydro-19-ol-ent-kauran-17-oic acid) (3), and a new norkaurane diterpenoid, annoglabasin F (16alpha-acetoxy-19-nor-ent-kauran-4alpha-ol-17-methyl ester) (4), along with 13 known kaurane derivatives were isolated from the stems of Annona glabra. 16alpha-Methoxy-ent-kauran-19-oic acid (5) and 16alpha-hydro-ent-kauran-17,19-dimethyl ester (6) were obtained for the first time as natural products. The structures of compounds 1-6 were characterized by spectral analysis.