Lyngbyabellins K-N from Two Palmyra Atoll Collections of the Marine Cyanobacterium Moorea bouillonii

Five lipopeptides of the lyngbyabellin structure class, four cyclic (13 and 5) and one linear (4), were isolated from the extracts of two collections of filamentous marine cyanobacteria obtained from the Palmyra Atoll in the Central Pacific Ocean. Their planar structures and absolute configurations were elucidated through a combination of spectroscopic and chromatographic analyses as well as chemical synthesis of fragments. In addition to structural features typical of the lyngbyabellins, such as two thiazole rings and a chlorinated 2-methyloctanoate residue, these new compounds possess several unique aspects. Of note, metabolites 2 and 3 possess rare monochlorination on the 3-acyloxy-2-methyloctanoate residue, whereas lyngbyabellin N (5) has an unusual N,N-dimethylvaline terminus. Lyngbyabellin N also possesses a leucine statine residue and shows strong cytotoxic activity against the HCT116 colon cancer cell line (IC50 = 40.9?+/-?3.3 nM).