New briarane stecholide diterpenes from the Indonesian gorgonian Briareum sp.

The Indonesian gorgonian Briareum sp. has afforded two new briarane stecholide diterpenes: 2,9-diacetyl-2-debutyrylstecholide H (1) and 13-dehydroxystecholide J (2), the semisynthetic 2 beta-acetoxy-2-(debutyryloxy)stecholide E acetate (3), which was isolated as a natural product for the first time, along with the known compounds stecholides I-M (4-8), stecholide A acetate (9), and stecholide C acetate (10). The structures of the new compounds were deduced by extensive NMR studies (H-1, C-13, H-1-H-1 COSY, NOESY, HMQC, and HMBC) and FABMS data (HR and LR). Cytotoxic activity was found for the first time in stecholide L (7).