Dimorpoloids A–D, Three Rearranged Diterpenoids and One Unique Daphnane-Type Diterpenoid from Dimorphocalyx poilanei

The first phytochemical investigation of Dimorphocalyx poilanei led to the isolation and characterization of four novel diterpenoids, namely, dimorpoloids A-D (1-4), along with two biosynthetically related known diterpenoids. Compounds 1 and 2 are rearranged ent-cleistanthane diterpenoids with a 6/7/6-fused tricyclic scaffold. Compound 3 is a rearranged 17-nor-ent-labdane-type diterpenoid, distinguished by a novel tropone ring system in its molecular architecture. Compound 4 represents the first daphnane-type diterpenoid featuring an aromatic C-ring system. Their structures were elucidated by spectroscopic analysis and quantum chemical calculations. Putative biosynthetic pathways for compounds 1-3 are proposed. Compounds 1 and 3-6 exhibited antiadipogenic effects in 3T3-L1 adipocytes, and the most potent compound 6 showed an EC50 value of 3.29 ± 0.53 μM.