Caesanines A–D, New Cassane Diterpenes with Unprecedented N Bridge from <i>Caesalpinia sappan</i>

Serial antibacterial furanoditerpenes caesanines A–D (<b>1</b>–<b>4</b>), possessing a cassane-type diterpenoid skeleton with an unusual N bridge between C-19/C-20, were identified from a Chinese herb <i>Caesalpinia sappan</i> Linn. In addition, caesanine D (<b>4</b>) showed the first class of dicassane diterpenoid ethers. Their structures were determined by different spectroscopic methods and ECD calculation. Caesanines A and B exhibited strong activities against MRSA suggesting a promising entry point for the development of anti-infective drugs