Two new sarasinosides from the sponge Melophlus sarasinorum

Abstract

Two new 30-norlanostane-type oligoglycosides (6, 7) along with five known sarasinosides A1 (1), A2 (2), A3 (3), M (4), L (5) were isolated from the ethanol extract of the Australian sponge Melophlus sarasinorum. The skeleton of new sarasinoside A4 (6) possesses a rare 8α,9α-oxido-8,9-seco-moiety. Sarasinoside A5 (7) proved to be a 9-deoxy-congener of the previously described sarasinoside L (5). Compounds 1-7 have identical pentasaccharide chains and differ in the aglycone portions. The structures have been elucidated on the basis of NMR, MALDI-TOF MS and GC analyses.