11-oxygenated cytotoxic 8,9-secokauranes from a New Zealand liverwort, Lepidolaena taylorii.

Four new cytotoxic 8,9-secokauranes have been identified from the liverwort Lepidolaena taylorii. The 11-oxygenation found in three of these has not been encountered in the 8,9-secokauranes known from higher plants. NMR studies were combined with molecular modelling to determine the preferred conformations. Six structurally related kauren-15-ones were also found, including three new compounds. Some of these compounds showed differential cytotoxic activity against human tumor cell lines. The probable mode of cytotoxic action was supported by Michael addition of a thiol. Two 8,9-secokauranes were the main cytotoxins in another New Zealand liverwort. L. palpebrifolia.