Symbiodinolide is a polyol marine natural product isolated from dinoflagellate Symbiodinium sp. This natural product exhibits voltage-dependent N-type Ca²⁺ channel-opening activity at 7 nM and COX-1 inhibition activity at 2 µM. The planar structure of symbiodinolide was elucidated by the detailed 2D NMR analysis. However, the huge and complex molecular structure of this molecule featuring a molecular weight of 2,860 and the presence of 61 chiral centers has hampered the complete stereochemical determination. Herein, we report our synthetic study of symbiodinolide toward the structural elucidation.