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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]

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]