Continuing studies on the cyanobacterium Lyngbya sp.:: Isolation and structure determination of 15-norlyngbyapeptin a and lyngbyabellin D

Re-collections of the cyanobacterium Lyngbya sp. have yielded two more members of the lyngbyapeptin and lyngbyabellin families. The gross structures of 15-norlyngbyapeptin A (1) and lyngbyabellin D (3) were deduced through standard 2D NMR techniques, with the absolute configuration of both elucidated through degradation and comparison with commercially available and synthetic standards. Degradation to the a-amino acid and NOE correlations determined the absolute and relative configuration of the 4-amino-3-hydroxy-5-methylhexanoic acid unit in 3. Lyngbyabellin D (3) displayed an IC50 value of 0.1 mM against the KB cell line.