Cacospongione A, cacospongienone A, and cacospongienone B, new C 21 difuran terpenoids from the marine sponge Cacospongia scalaris S CHMIDT of the Côte d' Azur

The sponge Cacospongia scalaris (family Thorectidae), collected at the Cap de Nice (Cǒte d'Azur), is shown to contain a series of truncated, linear C 21 difuran terpenoids comprising the known sponge products furospongin‐1 ((+)‐ 1 ), furospongin‐2 ( 2 ), and dihydrofurospongin‐2 ((−)‐( E )‐ 3 ), besides the new products cacospongione A ((−)‐ 4 ), cacospongienone A ((−)‐( Z )‐ 6 ), and cacospongienone B ((−)‐( E )‐ 6 ), whose absolute configurations have been assigned by chemical correlations with (+)‐ 1 . Possibly, one of the two cacospongienones is an artifact, as these two terpenoids interconvert on standing. This is the first finding of linear C 21 difuran terpenoids, which are typical of the Spongiidae, in a member of the family Thorectidae.