Ent-isopimarane diterpenoids from the Cameroonian Croton oligandrus Pierre ex Hutch

Ent-isopimarane diterpenoids have been isolated from extracts of the fruits, leaves and stem bark of the Cameroonian Croton oligandrus Pierre ex Hutch (Euphorbiaceae). The fruits yielded eight compounds, including the previously undescribed ent-19-hydroxyisopimara-8(9),15-dien-7-one (2), ent-isopimara-7(8),15-dien-6,19-diol (4) and ent-isopimara-7(8),15-dien-19-yl octadecanoate (5), the leaves yielded five compounds, again including ent-isopimara-7(8),15-dien-19-yl octadecanoate (5) and ent-19-hydroxyisopimara-8(9),15-dien-7-one (2). The stem bark yielded nine known compounds, including ent-isopimarane diterpenoids, clerodanes, triterpenoids and common phytosterols. The chemical structures of the compounds were determined using NMR, IR and MS experiments. The absolute configuration of the isopimarane diterpenoids was deduced using electronic circular dichroism (ECD) experiments.