The isolation and chamcterixation of two novel triterpene glycosides from a sponge of the genus &@Is, collected at a depth of 500 m in the South of New Caledonia, are described. The structures are charucterixed by the presence of a branched oligosacd&de chain, composed of three (1) and four (2) D-galactopyranose units, respectively. Analysis of the oligo~~&de structures was achieved by ['H, tH) correlation spectroscopy, two-dimensional homon~lear Hartmann-Hahn, and 'H-detected [*H t3C) one bond @&K&Z) and multiple-bond (HMBC) shift correlation NMR experiments. The'novel lanostane derived aglycone features a rare la-carboxyl gidup and a 24-methylene, 25methyl side chain.
lFWRODUCTION
Steroidal and triterpene oligoglycosides are the predominant metabolites of starfishes and sea cucumbers, respectively.lBesides these echinoderms, only a limited number of marine organisms have been shown to contain glycosides. For example, pregnane-or cholestane-type steroidal m~oglyc~id~ or diglycosides have been reported from soft coral@, ophiuroids~, gorgonian@ and fishes". More recentely glycosidea have also baen isolated from some sponges; several nor-lanostane-triterpenoid oligoglycosides from Asteropus mrasimum '.*, a 4methyl steroidal diglycoside from Erylus Jen&nkJ& and a steroidal saponin from PacJmtreJJa gem@'. In sea& of novel bioactive marine natural products from new-caledonian organisms, we have isolated two new lanostane derived triterpene oliiogalactosides, from a sponge of the genus E&us collected at a depth of 500 m in the South of New Caledonia.
In the present work we report the compIete stmctuml assigmt~ents of Eryloside C (I) and D (2k. Structure elucidation of oligosaccharide portions has been accomplished exclusively on the basis of two-dimensional proton-proton and proton-carbon chemical shitl correlation spectroscopy. a) Y. K&man et aI. gave the name erybside A to the 3~-O-[~~~~op~oayl-(l~2)-fi-Pgalactop~o~l]-23~-hydroxy-4u-~~yl-5a~~e~-8,14~e~, is&ted from &J&S kwdenkldi ' . In the same pper the Authors claim tbe isolation of e second glycoside, sssi8ned es eryloside B, dose stmchre is not yet de&mined (Y. Kashmm, personal information to one of the Authors, Jidgi Minale).