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The Australian rainforest plant, Croton insularis, has provided a further casbane diterpene family member in the form of EBC‐342, which contains a novel tetrahydrofuran ring. A combination of DP4 and TD‐DFT CD methods were required to confirm both structure and absolute stereochemistry. [ABSTRACT FROM AUTHOR]

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]

Investigation of the Australian rainforest plant Croton insularis led to isolation of the first casbane hydroperoxide diterpenes EBC-304 and EBC-320. Extensive DFT and electronic circular dichroism (ECD) calculations in combination with 2D NMR spectroscopy determined the absolute configurations. EBC-304 and EBC-320 both display significant cytotoxicity. [ABSTRACT FROM AUTHOR]

Two novel (EBC‐204 and EBC‐205), together with three known, halimanes were isolated from the Australian rainforest plant Croton insularis. EBC‐203 strongly inhibited K562 leukemia cell growth. Halimanes, which only a few decades ago were considered rare natural products, have been isolated from the Australian rainforest plant Croton insularis. New halimanes EBC‐204 and EBC‐205, along with the known halimane, crotohalimaneic acid, herein named EBC‐202, were characterized. [ABSTRACT FROM AUTHOR]

The seco-casbane framework, first isolated from Croton insularis, is surprisingly rare. Further evaluation of this Australian rainforest plant unearthed two additional members, EBC-328 and EBC-363. TD DFT predicted electronic circular dichroism (ECD) spectra were critical for remote absolute stereochemical determination. EBC-328 displayed cytotoxic activity towards leukemia cells (K562). Potential biosynthetic relationships are discussed. [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]

EBC-219 ( 4), isolated from Croton insularis (Baill), was established by spectroscopic and DFT methods as the first member of a new diterpene skeletal class, uniquely defined by the presence of a bicyclo[10.2.1] bridgehead olefin. The proposed biogenetic pathway to 4 from the co-isolated natural products EBC-131 ( 1), EBC-180 ( 2) and EBC-181 ( 3) is highly likely. EBC-180 ( 2) and EBC-181 ( 3) showed moderate to strong cytotoxic activity against various cancer cell lines. [ABSTRACT FROM AUTHOR]

Investigation of Croton insularis afforded the first in class seco-casbane diterpene, EBC-329. A highly oxidised casbane, EBC-324, was also isolated. The structural motif within EBC-324, which consists of an epoxidised hemi-acetal endoperoxide, is new to the casbane family. [ABSTRACT FROM AUTHOR]