Dolastanes from the brown alga Dilophus spiralis: absolute stereochemistry and evaluation of cytotoxicity

Five new dolastanes (1–5) were isolated from the brown alga Dilophus spiralis. The structural elucidation of the isolated compounds and the assignment of relative stereochemistry were based on analyses of their spectroscopic data. The structure proposed for 1 was confirmed by single crystal X-ray diffraction analysis, whereas its absolute stereochemistry was determined using the modified Mosherʹs method. The cytotoxicity of 1–4 was evaluated against seven cell lines.