Iakyricidins A–D,Antiproliferative PiericidinAnalogues Bearing a Carbonyl Group or Cyclic Skeleton from Streptomyces iakyrus SCSIO NS104

Iakyricidins A–D (1–4), a carbonyl-containing piericidin derivative and three novel piericidin analogues bearing cyclic skeletons, were isolated from the mangrove sediment derived strain Streptomyces iakyrus SCSIO NS104. These structures were established by spectroscopic techniques, Mosher’s method, and ECD calculations. Compounds 2–4 represent a novel skeleton of piericidins with branched chain C–C cyclization, and their biosynthetic pathways are proposed. Compound 1, the first natural carbonyl-containing piericidin derivate, exhibited potent antiproliferative activity against ACHN with an IC50 value of 20 nM.