Sesquiterpenoids of the Sponge Dysidea fragilis of the North‐Brittany Sea

The title sponge is shown to contain eight new sesquiterpenoids for which a common, unusual biogenetic origin is postulated. The compounds are shown to be: (–)‐(1 R *,4 R *)‐3‐(3′‐furyl)methyl‐2‐ p ‐menthen‐7‐yl acetate ((–)‐ 8b ); two diols separated as the monoacetates (–)‐(1 S *,4 R *)‐3‐(3′‐furyl)methyl‐l‐hydroxy‐2‐ p ‐menthen‐7‐yl acetate ((–)‐ 13a ) and the (–)‐(1 R *,4 R *)‐epimer (–)‐ 13b , the two C(4)‐epimeric 4‐ethoxy‐3‐(1′(7′),2′‐ p ‐menthadien‐3′‐yl)methyl‐2‐buten‐4‐olides ((+)‐ 14a and (–)‐ 14b ), (–)‐3‐(3′‐furyl)methyl‐7‐nor‐2‐ p ‐menthen‐l‐one ((–)‐ 11 ), (–)‐(3Z)‐1‐(3′‐furyl)‐4,8‐dimethylnona‐3, 7‐dien‐2‐yl acetate ((–)‐ 17 ), and (+)‐3‐(5′,7′‐seco‐2′(10′)‐pinen‐7′‐yl)methylfuran ((+)‐ 15 ).