Biofouling poses one of the most serious problems to marine industry and aquaculture development. Five structurally similar compounds were isolated from the crude extract of a marine Streptomyces strain. Antifouling activities of these compounds and four other structurally-related compounds isolated from another marine Streptomyces species were compared to generate structure–activity relationship data. Based on structure–activity relationship analysis, another compound with a simplified structure but excellent antifouling activities was synthesized. The optimized compound was synthesized by Medicilon.