Two new oxygenated terpenes ( and ) have been characterized from the Australian nudibranch . Broadened H NMR signals, together with the absence of individual carbon NMR signals, complicated analysis of 5,9-epoxydendrillolide A (); increasing the temperature to 323 K revealed the missing NMR signals. Low-temperature H NMR experiments provided an activation barrier of ∼15 kcal mol and, together with DFT calculations, supported interconversion of a twist chair conformer with two different chair conformers. X-ray crystallographic analysis coupled with biosynthetic reasoning suggested a (5, 8, 9, 13, 14, 15, 16) configuration. Ketone demonstrated similar dynamic conformational processes to .
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