Sesquiterpene isocyanides, isothiocyanates, thiocyanates, and formamides from the Thai sponge Halichondria sp.

Abstract Nine new nitrogenous sesquiterpenes ( 1 – 9 ) were isolated together with 11 known compounds ( 10 – 20 ) from the Thai marine sponge Halichondria sp. The structures of the isolated compounds were determined on the basis of extensive NMR studies and high-resolution MS measurements as well as comparison with literature data. Sixteen of these metabolites were evaluated for cytotoxic activity against six tumor cell lines.