New ent-Kaurane Diterpenoids with Anti-Platelet Aggregation Activity from Annona squamosa

A phytochemical investigation on the stems of Annona squamosa led to the isolation of six new ent-kaurane diterpenoids, annomosin A (16beta-hydroxy-19-al-ent-kauran-17-yl 16beta-hydro-19-al-ent-kauran-17-oate) (1), annosquamosin C (16alpha-hydro-17-hydroxy-19-nor-ent-kauran-4alpha-ol) (2), annosquamosin D (16beta-acetoxy-17-hydroxy-19-nor-ent-kauran-4alpha-ol) (3), annosquamosin E (16beta-hydroxy-17-acetoxy-19-nor-ent-kauran-4alpha-formate) (4),...