Actinobacteria have been extensively studied thus far, and they are known to produce pharmaceutically important compounds.1,2 Soil serves as the primary source of actinobacteria and, therefore, we attempted to obtain novel metabolites from actinobacteria isolated from soil samples. During our screening program for novel metabolites, a new metabolite possessing a thioester named JBIR-69 (1, Figure 1a), together with a known compound, 3-isopropylmalate methyl ester, was isolated from the culture broth of Streptomyces sp. OG05. This paper describes the fermentation, isolation, structural elucidation, and, in brief, the biological activity of 1.