Ircinia wistarii

C25H32O4, Mr 396.53, oil, [a]g +130 (CH2CI2). Diter-penoid constituent of Ircinia wistarii. 

A unique tetracyclic furanosesterterpene, wistarin (195), has been discovered in Ircinia wistarii in addition to the previously known isomer ircinianin (196) 131). 196 decomposed readily, whereas 195 was relatively stable. As wistarin (195) was not detected among the decomposition products of 196 and 196 did not undergo cyclization to 195 on treatment with dilute acid, base or Lewis acids, it was proposed that 195 was a natural product and not an artifact. The biosynthesis of these sesterterpenes must involve a different folding of the acyclic 25-precursor. 

Gregson, R.P., and D. Ouvrier Wistarin, a Tetracyclic Furanosesterterpene from the Marine Sponge Ircinia wistarii. J. Nat. Prod. 45, 412 (1982). 

Four unstable sulfate esters (373-376) of known furanosesterterpenes were obtained from Ircinia variabilis and from /. or os from the northern Adriatic Sea [328], The 22-O-sulfates of palinurin (377) and fasiculatin (378) were isolated from 7. variabilis and from /. fasiculata respectively. Both were toxic to brine shrimp [329]. Ircinianin sulfate (379) was isolated from /. (Psammocinia) wistarii from the Great Barrier Reef as a very unstable metabolite [330]. 

Coll, J.C., Kearns, P.S., Rideout, J.A., and Hooper, J. (1997) Irdnianin sulfate from the marine sponge Ircinia Psammocinia) wistarii. J. Nat. Prod., 60,1178-1179. 

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