A marine-derived Streptomyces strain, SSC21, was isolated from the sediment of Suncheon Bay, Republic of Korea. Chemical analysis of the bacterial strain resulted in the isolation of four new metabolites, suncheonosides A-D (1-4, respectively), each bearing a sulfur atom. The planar structures of the suncheonosides were identified as hexasubstituted benzothioate glycosides by combined spectroscopic analyses. Analysis of the configuration of the sugar moieties based on ROESY nuclear magnetic resonance correlations, one-bond (1)H-(13)C coupling constant analysis, and chemical derivatizations indicated that the suncheonosides incorporate only l-rhamnose. Suncheonosides A, B, and D promoted adiponectin production in a concentration-dependent manner during adipogenesis in human mesenchymal stem cells, suggesting antidiabetic potential.