Linear and cyclic C18 terpenoids from the Southern Australian marine brown alga Cystophora moniliformis

Chemical investigation of the Southern Australian marine brown alga Cystophora moniliformis resulted in the isolation of two new cyclic epmeric terpene diols, moniliforminol A (25) and moniliforminol B (26), a new linear farnesylacetone derivative (27), and the previously described terpenoids 19-24. This study also resulted in the first complete 2D NMR characterization for compounds 21 to 24 as well as the first report of 24 as a natural product. All structures were elucidated by detailed spectroscopic analysis, with the relative configurations of 25 and 26 being established by selective 1D NOE NMR experiments. The absolute configuration of 26 wits assigned on the basis of circular dichroism (CD), which also permitted that of 25 to be tentatively assigned.