Two new, 1-oxygenated ent-kaurane-type diterpenes from Croton kongensis

One new ent-8,9-secokaurane diterpene, kongensin D (1), and one new ent-kaurane diterpene, kongensin E (2), along with one known compound, (7 alpha) -7,18-dihydroxy-ent-kaur-16-en- 15 -one 18-acetate (3), were isolated from the aerial parts of Croton kongensis. The structures of the new compounds were elucidated by means of HR-MS and in-depth NMR experiments, and by comparison with literature data. Compounds I and 2 showed an unusual oxygenation pattern with an OH or AcO group at C(l).