Hemslecin C, a compound with a novel skeleton, is synthesized by refluxing hemslecin A with KOH in alcohol. Hemslecin C was structurally characterized by specific optical rotation measurement, high-resolution mass spectroscopy, and nuclear magnetic resonance spectroscopic analysis. In addition, the molecular structure of hemslecin C was unambiguously determined by X-ray single-crystal determination. We found that its structure was different from that reported in the literature. The acetyl group of hemslecin A is transferred to the...