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Structurally unique halimanes EBC‐232 and EBC‐323, isolated from the Australian rainforest plant Croton insularis, proved considerably difficult to elucidate. The two diastereomers, which consist an unusual oxo‐6,7‐spiro ring system fused to a dihydrofuran, were solved by unification and consultation of five in silico NMR elucidation and prediction methods [i.e. ACDLabs, olefin strain energy (OSE), DP4, DU8+ and TD DFT CD]. Structure elucidation challenges of this nature are prime test case examples for empowering future AI learning in structure elucidation. [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]

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]

Five new pimarane and related-type diterpenes (i.e. EBC-316, 325-327, and 345 (10-15)), together with two known pimaranes (EBC-221 (8) and EBC-346 (9)), were isolated from the stems of Croton insularis, found in the Australian rainforest. All pimarane diterpenes disclosed herein are suggested to be biogenetically related to the same keto-Jacobs- Reynolds intermediate 2, via ring A and C oxidation. Anticancer activities of compounds 11-13 are reported. [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]

Two novel seco-casbanes EBC-328 (I) and EBC-363 (II) from the australian rainforest plant Croton insularis. [ABSTRACT FROM AUTHOR]