New brominated labdane diterpenes from the red alga Laurencia obtusa.

Two labdane type brominated diterpenes (1 and 2) containing unprecedented eight- and seven-membered ether rings have been isolated from the organic extract of the red alga Laurencia obtusa, collected from Mitikas Bay in the Ionean Sea, Greece. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analysis, including 2D NMR experiments.

Novel cytotoxic brominated diterpenes from the red alga Laurencia obtusa.

Five new brominated diterpenes, along with two known, have been isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Preveza in the Ionean Sea, Greece. The novel metabolites prevezols B-E possess two new carbon skeletons, to the best of our knowledge, unprecedented in the literature. The structures and the relative stereochemistry of the new natural products were established by means of spectral data analyses.