Sarsolenane and Capnosane Diterpenes from the Hainan Soft Coral Sarcophyton trocheliophorum Marenzeller as PTP1B Inhibitors

Two new sarsolenane diterpenes, dihydrosarsolenone (2), methyl dihydrosarsolenoneate (3), and two new capnosane diterpenes, sarsolilides B (5) and C (6), were isolated together with the known analogue, sarsolilide A (4), from the Hainan soft coral Sarcophyton trocheliophorum Marenzeller. Their structures were elucidated by detailed spectroscopic analysis and by comparison with reported data, leading to a structure revision of sarsolenone (1). The absolute configurations of 2 and 5 were determined by TDDFT ECD calculations, and they could be used as ECD reference compounds in the determination of the absolute configuration of their related derivatives. Compounds 4 and 5 exhibited inhibitory activity in vitro against protein tyrosine phosphatases 1B (PTP1B), representing the first report of PTP1B inhibitory activity for capnosane diterpenes. Sarsolenane diterpenes 2 and 3 and capnosane diterpenes 5 and 6 were isolated from the Hainan soft coral S. trocheliophorum. The absolute configurations of 2 and 5 were determined by TDDFD ECD calculations, affording the configurational assignment of other analogues by ECD comparison or by biogenetic correlations. Compound 4 showed PTP1B inhibitory activity with IC50 values of 6.8 μM.