Thorectandrols C, D, and E, new sesterterpenes from the marine sponge Thorectandra sp.

Extracts of the marine sponge Thorectandra sp. have been found to contain three new sesterterpenes, thorectandrols C (4), D (5), and E (6), together with the known compounds luffarin R (7), luffarin V (8), and palauolide (9). The structures were determined by extensive NMR spectral data analysis. Their relative stereochemistry was defined using NOE correlations and coupling constants, while CD data were used to suggest their absolute stereochemistry. Cytotoxicity data for compounds 4-9 as well as the previously reported compounds thorectandrols A and B and palauolol (1-3) against six or more human tumor cell lines are also reported.