Axiriabilines A-D, uncommon nitrogenous eudesmane-type sesquiterpenes from the Hainan sponge Axinyssa variabilis

Abstract Four new uncommon nitrogenous eudesmane-type sesquiterpenes, axiriabilines A−D ( 1 – 4 ), and two known related ones ( 5 and 6 ), were isolated from the Hainan sponge Axinyssa variabilis . The structures of the new compounds were elucidated on the basis of extensive spectroscopic analysis and by comparison of their NMR data with those reported in the literature. The absolute configurations of compounds 1 and 4 were determined by TDDFT ECD calculations. All the new compounds were found to exhibit no cytotoxicity against several cancer cells.