Cembranoid constituents from an Australian collection of the soft coral <i>Sinularia flexibilis</i>

Two new cembranoid lactones have been isolated from Barrier Reef collections of Sinularia flexibilis. Other metabolites include four previously reported macrocyclic diterprenes. The structure and relative configuration of flexibilide (4), C20H30O4, was determined by single- crystal X-ray diffraction methods. The colourless crystals are orthorhombic, space group P212121, a 10.682, b 30.404, c 5.779 ?, Z 4.