*Communication* **Unique Cyclized Thiolopyrrolones from the Marine-Derived** *Streptomyces* **sp. BTBU20218885**

**Fuhang Song 1,†, Jiansen Hu 2,†, Xinwan Zhang 3, Wei Xu 3, Jinpeng Yang 3, Shaoyong Li 4 and Xiuli Xu 3,\***


† These authors contributed equally to this work.

**Abstract:** Two new cyclized thiolopyrrolone derivatives, namely, thiolopyrrolone A (**1**) and 2,2- dioxidothiolutin (**2**), together with the kn own compound, thiolutin (**3**) were identified from a marinederived *Streptomyces* sp. BTBU20218885, which was isolated from a mud sample collected from the coastal region of Xiamen, China. Their chemical structures were determined using spectroscopic data, including HRESIMS, 1D and 2D NMR techniques. **1** possessed a unique unsymmetrical sulfur-containing thiolopyrrolone structure. All the compounds were tested for bioactivities against *Staphylococcus aureus*, *Escherichia coli*, Bacille Calmette–Guérin (BCG), *Mycobacterium tuberculosis*, and *Candida albicans*. **1** displayed antibacterial activities against BCG, *M. tuberculosis*, and *S. aureus* with minimum inhibitory concentration (MIC) values of 10, 10, and 100 μg/mL, respectively. Thiolutin (**3**) showed antibacterial activities against *E. coli*, BCG, *M. tuberculosis*, and *S. aureus* with MIC values of 6.25, 0.3125, 0.625, and 3.125 μg/mL, respectively.

**Keywords:** marine-derived *Streptomyces*; thiolopyrrolone; antibacterial; *M. tuberculosis*
