Revised structure and synthesis of celastramycin a, a potent innate immune suppressor.

After searching for natural substances that regulate innate immunity using the ex vivo Drosophila culture system, a benzoyl pyrrole-type compound, celastramycin A, was identified and isolated as a potent suppressor. By synthesizing the previously reported structure 1 and another benzoyl pyrrole-type compound 2 reported in a Japanese patent, the correct structure of celastramycin A was confirmed to be 2. Compound 2 suppressed the production of IL-8 (IC(50) 0.06 microg/mL) in human umbilical vein endothelial cells (HUVECs).