New Triterpenoid Saponins from the Sponge Melophlus isis

Four new triterpenoid saponins were isolated, along with two known 30-norlanostane-type saponins sarasinosides A1 (1) and A3 (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 9α,15α- and 9α,15β-positions and the pentasaccharide portion identical with those of 1 and 2 at the 3β position, by spectral, chemical, and GC analyses.