Structurally diverse new alkaloids from Palauan collections of the apratoxin-producing marine cyanobacterium Lyngbya sp.

Various collections of the apratoxin-producing marine cyanobacterium Lyngbya sp. from Palau have afforded several new nitrogenous metabolites. Lyngbyabellin C is a dichlorinated, thiazole hydroxy acid-containing, cytotoxic macrolide that is related to other lyngbyabellins, to dolabellin, and to hectochlorin. Its selective decomposition tendency to form homohydroxydolabellin suggests that the sea hare isolate dolabellin may be an isolation artifact. In addition to the known lyngbyapeptin A, two new related modified tetrapeptides, lyngbyapeptins B and C, have been isolated. Furthermore, a new cytotoxic N-acylpyrrolinone, termed palauʹimide, was found. Structure elucidation of these metabolites involved extensive application of NMR spectroscopy.