Lemnalemnanes A-C, Three Rare Rearranged Sesquiterpenoids from the Soft Corals Paralemnalia thyrsoides and Lemnalia sp.

Three novel sesquiterpenoids, lemnalemnanes A-C ( 1 - 3 ), were obtained from marine soft corals Paralemnalia thyrsoides and Lemnalia sp. Their structures were determined by 1D/2D NMR spectroscopy, HRESIMS, single-crystal X-ray diffraction analysis (Cu Kα), Mosher's method, and ECD quantum chemistry calculations. Lemnalemnane A ( 1 ) possessed an intriguing basket-like structure with a spiro[bicyclo[3.3.1]nonane-furan core, while lemnalemnanes B ( 2 ) and C ( 3 ) exhibited unusual 6/6/5 and 6/5/5 carbon skeletons, respectively. In the proposed biosynthesis pathway, 1 - 3 were suspected to originate from the same precursor, 4- O -deacetylparalemnolin D ( 4 ), a compound coisolated from both aforementioned species. Furthermore, lemnalemnane C ( 3 ) exhibited strong in vivo promoting-angiogenesis activity.