Antibacterial p‑Terphenyl with a Rare 2,2′-Bithiazole Substructure and Related Compounds Isolated from the Marine-Derived Actinomycete Nocardiopsis sp. HDN154086

Assisted by MS/MS-based molecular networking and X-ray diffraction analysis, five newp-terphenyl derivatives, namely, nocarterphenyls D-H (1-5), were obtained and characterized from the cultures of the marine sediment-derived actinomyceteNocardiopsissp. HDN154086. The skeleton of nocarterphenyl D (1) was defined to possess a rare 2,2′-bithiazole scaffold, naturally occurring for the first time, and nocarterphenyls E-H (2-5) arep-terphenylquinones with unusual thioether linked fatty acid methyl ester substitutions. Compound1showed promising activity against multiple bacteria with MIC values ranging from 1.5 to 6.2 μM, and2exhibited notable antibacterial activity against MRSA which surpassed the positive control ciprofloxacin.