A novel 37-membered macrolides, theonezolides A similar to C, and two novel manzamine-related alkaloids, nakadomarin A and ma'eganedin A, were isolated from Okinawan marine sponges, while three new polyhydroxyl compounds, luteophanols A similar to C, were obtained from a marine dinoflagellate. The structures were elucidated on the basis of the spectroscopic data. The absolute stereochemistry of the C-4 similar to C-17 fragment of theonezolides A similar to C was established by synthetic studies, and a plausible biogenetic path of nakadomarin A was proposed.