New α-Pyridones with Quorum-Sensing Inhibitory Activity from Diversity-Enhanced Extracts of a Streptomyces sp. Derived from Marine Algae

Four new α-pyrones (1–4) and eight known analogues (5–12) were identified from the secondary metabolites of Streptomyces sp. OUCMDZ-3436 derived from the marine green algae Enteromorpha prolifera. Seven new α-pyridones (14–20) were constructed by diversity-oriented synthesis, which has been an effective approach to expanding the chemical space of natural-product-like compounds. Compounds 16, 17, 19, and 20 were found to have inhibitory effect on the gene expression controlled by quorum sensing in Pseudomonas aeruginosa QSIS-lasI.