Aromatic Polyketides from the Mangrove-Derived Streptomyces sp. SCSIO 40069

A chemical investigation of Streptomyces sp. SCSIO 40069 resulted in the isolation of a series of aromatic polyketides with rare skeletons, including five new compounds RM18c–RM18g (1–5) and three known ones (6–8). Their structures and absolute configurations were determined by diverse methods, including HRMS and NMR spectra, chemical reaction, Snatzke’s method, quantum mechanical–nuclear magnetic resonance (QM-NMR), and X-ray crystallographic analysis. Compounds 1, 2, 4b, and 8 displayed moderate or weak antibacterial activities.