Biosynthesis of isocyanoterpenes in sponges

A marine sponge from Hawaii, Ciocalypta sp., incorporated [¹⁴C]cyanide (1.8%) into 2-isocyanopupukeanane (8). Doubly labeled [¹³C,¹⁵N]cyanide was incorporated intact (1.46%) into 9-isocyanoneopupukeanane (10). Another sponge, Acanthella sp., from Guam incorporated [¹⁴C]cyanide (1.5%) into kalihinol-F (11). Labeled 11 was transformed into the corresponding triamine and hence the trisbenzylurea, which after purification was devoid of radioactivity, thereby proving that cyanide serves as specific precursor for the isocyano function.