Cytotoxic Kendomycins Containing the Carbacylic <i>Ansa</i> Scaffold from the Marine-Derived <i>Verrucosispora</i> sp. SCSIO 07399

Three new kendomycin analogues, kendomycins B–D (1–3), were discovered from the marine-derived actinomycete Verrucosispora sp. SCSIO 07399. The structures of 1–3 were elucidated using diverse spectroscopic data analyses, X-ray crystallography, and semisynthetic derivatization. In vitro antimicrobial assays revealed that 1–3 all display good antibacterial activities against six Gram-positive bacteria with MIC values ranging from 0.5 to 8.0 μg/mL. Additionally, 1–3 were found to be moderately cytotoxic against MGC803, A549, HeLa, HepG2, MCF-7, and RKO human tumor cell lines; IC50 values ranged from 2.2 to 44 μM.