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Investigation of the Australian rainforest plant Croton insularis revealed seven new cis‐, two new trans‐cyclopropane casbanes, and the first trans‐cyclopropane seco‐casbane. The relative configuration of the cyclopropane moiety for all compounds (EBC‐182, 217, 218, 220, 343, 357, 358, 361, 365, 373; EBC=EcoBiotics Compound) was assigned using 13C NMR data. Comparison of the experimental electronic circular dichroism (ECD) spectra with the theoretical curves, calculated by TD‐DFT at the B3LYP/6‐31+G**//B3LYP/6‐31+G** level, in conjunction with NOE data afforded the absolute configuration. EBC‐180, 181 and 220 displayed potent activity against cervical carcinoma (HeLa cells). Ask for casbanes andCrotongiveth: The Australian rainforest plant Croton Insularis revealed new cis‐ and trans‐casbanes, along with the first trans‐seco‐casbane. Absolute configuration of all 10 casbanes was determined by ECD and one derivative displayed potent activity against HeLa cells. [ABSTRACT FROM AUTHOR]

EBC-162 isolated from Croton insularis, obtained from the northern rainforest of Australia, was structurally affirmed as crotofolin C ( 4). Novel oxidative degradation products, EBC-233 and EBC-300, which are the first crotofolane endoperoxides, were also isolated. Both endoperoxides were found to be stable intermediates, which are proposed to undergo an unprecedented homo-Baeyer-Villiger biosynthetic rearrangement to give a new class of 1,14- seco-crotofolane diterpenes. Prolonged storage of all isolates assisted in authenticating their natural product status. Anticancer activities of reported compounds are presented. [ABSTRACT FROM AUTHOR]