Oppositane-Type Sesquiterpenoids from the Formosan Soft Coral Sinularia leptoclados

Two new natural products, the oppositane-type sesquiterpenoids leptocladolins A and B (1 and 2), along with two known compounds 1 beta-hydroxy-6 alpha-acetoxyeudesm-4(15)-ene (3) and 1 beta,6 alpha-dihydroxyeudesm-4(15)-ene (4) were obtained from a Formosan soft coral Sinularia leptoclados. The relative structures of 1 and 3 were confirmed by X-ray diffraction analysis. The absolute structures of 1 and 3 were determined by the Mosher's method. It was found that 4 significantly inhibited the upregulation of pro-inflammatory iNOS protein in LPS-stimulated RAW264.7 macrophage cells.