New triterpenoid saponins from the sponge Melophlus isis

Four new triterpenoid saponins were isolated, along with two known 30-norlanostane-type saponins-sarasinosides A(1) (1) and A(3) (2)-from the sponge Melophlus isis collected from Guam. The structures of these new compounds (3-6) proved to be 30-norlanosta-8(14),24-dien-23-ones bearing two hydroxyl groups or the corresponding methoxy groups at the 9 alpha,15 alpha- and 9 alpha,15 beta-positions and the pentasaccharide portion identical with those of 1 and 2 at the 3 beta position, by spectral, chemical, and GC analyses.