Sphaeroane and Neodolabellane Diterpenes from the Red Alga Sphaerococcus coronopifolius

Investigation of minor metabolites in the extracts of the red alga Sphaerococcus coronopifolius collected from the rocky coasts of Corfu Island in the Ionian Sea yielded two new diterpene alcohols, sphaerollanes I,and II (1, 2) featuring neodolabellane skeletons, and the new sphaeroane diterpene alcohol 16-hydroxy-9S*-acetoxy-8-epi-isosphaerodiene-2 (3), along with two previously reported metabolites 4, 5. The structures of the new natural products, as well as their relative stereochemistry, were elucidated on the basis of extensive spectral analysis, including 2D-NMR experiments.